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In response to herbivory, plants emit volatile compounds that play important roles in plant defense. Herbivore-induced plant volatiles (HIPVs) can deter herbivores, recruit natural enemies, and warn other plants of possible herbivore attack. Following HIPV detection, neighboring plants often respond by enhancing their anti-herbivore defenses, but a recent study found that herbivores can manipulate HIPV-interplant communication for their own benefit and suppress defenses in neighboring plants. Herbivores induce species-specific blends of HIPVs and how these different blends affect the specificity of plant defense responses remains unclear. Here we assessed how HIPVs from zucchini plants (Cucurbita pepo) challenged with different herbivore species affect resistance in neighboring plants. Volatile “emitter” plants were damaged by one of three herbivore species: saltmarsh caterpillars (Estigmene acrea), squash bugs (Anasa tristis), or striped cucumber beetles (Acalymma vittatum), or were left as undamaged controls. Neighboring “receiver” plants were exposed to HIPVs or control volatiles and then challenged by the associated herbivore species. As measures of plant resistance, we quantified herbivore feeding damage and defense-related phytohormones in receivers. We found that the three herbivore species induced different HIPV blends from squash plants. HIPVs induced by saltmarsh caterpillars suppressed defenses in receivers, leading to greater herbivory and lower defense induction compared to controls. In contrast, HIPVs induced by cucumber beetles and squash bugs did not affect plant resistance to subsequent herbivory in receivers. Our study shows that herbivore species identity affects volatile-mediated interplant communication in zucchini, revealing a new example of herbivore defense suppression through volatile cues.

The squash bug, Anasa tristis (De Geer) is a serious pest of cucurbit crops. The egg parasitoid, Gryon pennsylvanicum (Ashmead), is the primary parasitoid of the squash bug and has been considered ...

Squash bug, Anasa tristis DeGeer (Hemiptera: Coreidae), is a major pest of squash and pumpkins in the United States. In order to better understand the importance of natural egg parasitism of this species in Virginia, we conducted a 2-yr statewide survey. In total, 1,127 squash bug egg masses (~20,000 total eggs) were sampled from squash and pumpkins from 43 counties in Virginia from 2014 to 2015. Egg masses were brought back to the lab to record levels of squash bug nymphal emergence or adult parasitoid eclosion and identification. Over 50% of the total squash bug eggs collected statewide were parasitized. Gryon pennsylvanicum Ashmead (Hymenoptera: Scelionidae) was the predominant egg parasitoid accounting for over 98% of all parasitoid adults recovered. The only other species emerging from squash bug eggs was Anastatus reduvii Howard (Hymenoptera: Eupelmidae), which is a generalist parasitoid. G. pennsylvanicum was found in 75% of the counties surveyed with the highest levels of parasitism occurring in the Northern, Southwestern Mountain, and Western Piedmont regions of the state and the lowest levels of parasitism occurring in the Tidewater region in the southeastern portion of the state. Based on this 2-yr survey, G. pennsylvanicum was determined to be a major natural enemy of squash bug, significantly reducing the number of nymphs that emerge from deposited eggs. Conservation of this natural enemy should therefore be a priority for integrated pest management programs in cucurbits.

The squash bug, Anasa tristis (De Geer), is a major pest of squash, pumpkin, and other cucurbits throughout North America. A. tristis is a piercingsucking feeder that causes extensive foliar wilting and fruit scarring and transmits plant pathogens. Current biological agents to control A. tristis are limited in efficacy, and newer control methods must be developed. Here we present studies of immune system transcripts as the initial step in identifying potentially vulnerable targets for control of gene expression. Following immune stimulation with bacteria, transcript levels of six components of the inducible innate system in adult female A. tristis were measured using quantitative PCR. An antibacterial peptide-encoding transcript, anacin; an enzyme central to melanization, prophenoloxidase; and three sentinel proteins, scavenger receptor, β-1,3-glucan-binding protein, and peptidoglycan-binding protein were upregulated by bacterial elicitation. Expression of a putative immunoregulatory cytokine, astakine, was identified and increased by septic puncture. We also found novel upregulation of an enzyme of central energy metabolism, arginine kinase, in response to septic puncture of A. tristis adults.

Seasonal changes in egg parasitism and predation rates on sentinel (laboratory-reared) and wild (naturally occurring) egg masses of the squash bug, Anasa tristis (De Geer), were evaluated in squash fields in Maryland from June through September in 2013 and 2014. Rates of egg parasitism were significantly higher on wild egg masses than on sentinel egg masses. Squash bug nymphal emergence was significantly higher on sentinel egg masses than on wild egg masses. Between the first week of July and the first week of September of both survey years, squash bug nymphs emerged from 24.2% of wild eggs compared with 46.2% of sentinel eggs and parasitoids emerged from 55.7% of wild eggs compared with only 21.8% of sentinel eggs. Sentinel egg masses significantly underestimated the rate of natural egg parasitism. The egg parasitoid, Gryon pennsylvanicum (Ashmead), was responsible for over 99% of parasitism of squash bug eggs. There was a significant negative correlation between parasitoid emergence and nymphal emergence, suggesting that parasitoids were able to suppress squash bug populations. The average rate of parasitoid emergence peaked on wild egg masses on the fifth week of July at 72.8%, whereas the average rate of nymphal emergence from wild egg masses was

The squash bug, Anasa tristis, is a pest of cucurbits that exerts direct damage on crops and is a vector of plant pathogens. We established cell lines from this insect to serve as tools for basic biology, including virology and immunology, as well as applied studies, such as insecticide development programs. We initiated 15 cell cultures, using nine media or combinations of media. The media yielding the best results were a modification of Kimura's medium and a combination of two commercially available cell culture media (EX-CELL 420 and L15). We designated the two cell lines as BCIRL-AtE-CLG11 and BCIRL-AtE-CLG15. From the AtE-CLG15 line, we isolated two sub-lines, A and B. Of these, the most consistently replicating line was AtE-CLG15A. We determined the doubling time of this line (190 h) and its mean cell diameter (14.5 ± 0.7 μm). We characterized the AtE-CLG15A line using DAF-PCR. The BCIRL-AtE-CLG15A cell line is now available for researchers world-wide.

The squash bug, Anasa tristis (DeGeer) (Hemiptera: Coreidae), is an indigenous pest of squash and other cucurbits. Pesticides can control squash bug populations although many small-scale growers in the Southeast seek alternative methods of management. Cultural control methods, including varying the planting date and farmscaping, are not well understood under southeastern conditions. The goal of farmscaping is to increase natural ecosystem functions to aid in the control of pest populations. In the summers of 2014 and 2015, field plots of squash, separated by a minimum of 150 m were organized in a split-split plot design, with floral resources at the whole-plot level and varied planting date at the subplot level. Data were collected on squash bug abundance and fruit yield (kg), and abundance of potential natural enemies of A. tristis. Plots with added floral resources had fewer squash bug adults than plots without added floral resources in four of eight possible year × site × planting date combinations. Furthermore, the site in 2014 which had a reduction in squash bug adult abundance also had an increase in the abundance of potential enemies, including spiders, ground beetles, and predaceous Hemiptera. There were additional instances when potential natural enemy abundance was greater in resource-enhanced plots, but they were not associated with sites that had a reduction in yield loss or squash bug abundance. The use of floral resources to attract natural enemies and beneficial insects merits further investigation.

Plant chemicals mediating interactions with insect herbivores seem a likely target for manipulation by insectvectored plant pathogens. Yet, little is currently known about the chemical ecology of insect-vectored diseases or their effects on the ecology of vector and nonvector insects. We recently reported that a widespread plant pathogen, Cucumber mosaic virus (CMV), greatly reduces the quality of host-plants (squash) for aphid vectors, but that aphids are nevertheless attracted to the odors of infected plants—which exhibit elevated emissions of a volatile blend otherwise similar to the odor of healthy plants. This finding suggests that exaggerating existing host-location cues can be a viable vector attraction strategy for pathogens that otherwise reduce host quality for vectors. Here we report additional data regarding the effects of CMV infection on plant interactions with a common nonvector herbivore, the squash bug, Anasa tristis, which is a pest in this system. We found that adult A. tristis females preferred to oviposit on healthy plants in the field, and that healthy plants supported higher populations of nymphs. Collectively, our recent findings suggest that CMV-induced changes in host plant chemistry influence the behavior of both vector and non-vector herbivores, with significant implications both for disease spread and for broader community-level interactions.

Retention or loss of transmissibility after molting was tested for adult and nymphal squash bug, Anasa tristis (De Geer), a natural vector of the plant pathogen Serratia marcescens Bizio, the causal agent of cucurbit yellow vine disease. Squash bug adults and nymphs fed from bacteria-infiltrated squash cubes were caged on squash test plants and transferred weekly to new plants for eight consecutive weeks. Twelve percent of the bugs that acquired as adults transmitted the bacterium to at least one of the test plants; 75% of these transmitters inoculated more than one plant. Transmission to plants occurred as late as 3 to 8 weeks postacquisition. Ten percent of squash bugs that fed on S. marcescens as fifth instars inoculated plants after molting to the adult stage; 77% of these transmitters inoculated more than one plant. Two insects that fed on S. marcescens as third instars inoculated squash plants. When examined by scanning electron microscopy, the foregut cibaria of transmitting insects were free of bacteria-like structures. The ability of A. tristis to transmit S. marcescens after molting to the adult stage suggests that the hemocoel acts as the site of retention of transmissible bacteria.

Cucurbit yellow vine disease (CYVD), which can inflict heavy losses to watermelon, pumpkin, cantaloupe, and squash in U.S. production areas from the midwest to northeastern states, causes phloem discoloration, foliar yellowing, wilting, and plant decline. Bacteria were cultured from the phloem of crown sections of symptomatic plants of Citrullus lanatas and Cucurbita pepo. Those bacteria testing positive in CYVD-specific polymerase chain reaction (PCR) were all gram negative and appeared morphologically identical, producing creamy white, smooth, entire, convex colonies on Luria-Bertani or nutrient agar. Characterized cucurbit-derived strains of Serratia marcescens were introduced into greenhouse-grown squash plants by puncture inoculation and into field-grown squash plants by enclosure with S. marcescens-fed squash bugs, Anasa tristis. Up to 60% of the bacteria-inoculated plants in the greenhouse and up to 17% of field plants caged with inoculative squash bugs developed phloem discoloration and tested positive for S. marcescens by CYVD-specific PCR. None of the controls developed phloem discoloration or tested positive by PCR. Of the diseased field plants, 12% (2 of 35) also yellowed, wilted, and collapsed, exhibiting full symptom development of CYVD. However, neither plant collapse nor decline was observed in the greenhouse-grown, puncture-inoculated plants. The morphology, growth habit, and PCR reaction of bacteria cultured from crown tissue of a subset of plants in each experimental group were indistinguishable from those of the inoculum bacteria. Evidence presented from our studies confirms that the squash bug can transmit S. marcescens, the CYVD causal bacterium. The S. marcescens-A. tristis relationship described here is the first instance in which the squash bug has been identified as a vector of a plant pathogen. Our experiments represent a completion of the steps of Koch's postulates, demonstrating that S. marcescens is the causal agent of CYVD and that the squash bug, A. tristis, is a vector of the pathogen.

Summary • Compared with leaf-feeding herbivores, little is known about how sap-feeding herbivores affect plant growth, morphology and reproduction. This study examines effects of the sap-feeding squash bug ( Anasa tristis ) on watermelon ( Citrullus lanatus ) root, leaf and reproductive structures. • Plants at the four-leaf stage were exposed to different densities of caged squash bugs for 67 d (to plant maturity). • Initial effects were on roots. Herbivory was associated with a significant reduction in mean total root length, root surface area and number of root tips, as well as an increase in root diameters. Herbivore-exposed plants had significantly more leaves, although leaf lifespan was decreased. Both total plant dry mass and fruit dry mass per unit leaf area were significantly greater in controls. Significant effects of herbivores on plant reproductive traits included delayed flower formation (by 7–12 d), change in floral sex ratio (in favor of femaleness), increased fruit abortion, and smaller fruit size. • Developmental consequences were related to changes in plant water relations, including decreased water-use efficiency. Water use in treated plants was three to nine times greater per unit of plant dry mass than in controls.

The early development and feeding behavior of larvae of Anasa tristis (DeGeer) on cucumber, Cucumis sativus L., and pumpkin, Cucurbita pepo L., were compared. First-instar A. tristis development is similar on pumpkin, cucumber, and water alone. Second-instar A. tristis develop to 3rd instar on pumpkin but do not gain substantial weight on cucumber or water alone. Reduction in feeding is at least partly responsible and could be entirely responsible for lack of growth of 2nd-instar A. tristis on cucumber. Both initiation of feeding and feeding duration are reduced. However, 2nd-instar A. tristis can extract nutrients from plants that are not suitable for development. Feeding behavior of 2nd-instar A. tristis may reflect a balance between subsisting on available plants and moving to a suitable plant.

Finding and acceptance behaviors of Anasa tristis were investigated using plants that are suitable (pumpkin) or unsuitable (cucumber, coleus) for development. A. tristis found plants in the absence of non-contact cues. Plant finding is enhanced by olfaction and vision. A. tristis found suitable and unsuitable plants equally well. The importance of olfaction in plant acceptance is suggested by intense antennation while on plant and change in behavior on pumpkin and coleus after removal of antennae. Insects on suitable and unsuitable plants dab the surface, contact the plant surface with the labium and insert stylets. Post ingestive effects are important for plant acceptance and rejection. Ingesting water and some nutrients from plants unsuitable for development can be important in extending the time available to move between resource patches.

We conducted laboratory experiments on two field-collected populations of the squash bug, [Anasa tristis (De Geer) (Hemiptera: Coreidae)], to compare their responses to five generations of selection on a resistant squash cultivar ‘Waltham Butternut’, a susceptible cultivar ‘Early Prolific Straightneck’, or alternating generations on the resistant and susceptible cultivars. Before testing, one population was maintained for 1 generation on susceptible squash plants, while the other was maintained on the same cultivar for 5 generations. In both populations, nymphal survival decreased markedly in the first generation on resistant squash, but then approximately doubled in the second generation reared on the resistant cultivar. By the end of the experiments, survival on the rearing host was the same for A. tristis maintained continuously on a single cultivar, regardless of which cultivar. Immediately following one or more generations on resistant plants, A. tristis nymphs had lower survival on the susceptible cultivar than did nymphs that had been maintained for consecutive generations on the susceptible cultivar. Results of reciprocal crosses between lines of A. tristis reared on either resistant or susceptible squash for five generations indicated a genetic basis for differences in nymphal survival on the two cultivars. In contrast with the changes in nymphal survival, the preoviposition period became progressively longer when A. tristis was reared for several generations on the resistant cultivar compared to the susceptible one. Prior rearing on resistant plants increased the preoviposition period of adults placed on susceptible plants. However, adult feeding on resistant plants following nymphal development on susceptible plants did not result in an increase in the preoviposition period on resistant plants. Our findings indicate that squash bugs can adapt to resistant plants within a relatively short period in the laboratory. However, ecological and agricultural factors should prevent squash bugs from overcoming resistance in the field.

Field releases of the indigenous egg parasitoid Crayon pennsylvanicum (Ashmead) resulted in a 4-fold reduction in squash bug, Anasa tristis (De Geer), densities on ‘Jack-O-Lantern’ pumpkins in 1991. However, pest populations subjected to parasitoids were consistently higher, and fruit yields and quality lower, than on plants that were treated with the insecticide, esfenvalerate, When the squash bug-resistant ‘Green-Striped Cushaw’ was used, the difference in pest densities on parasitoid-released and insecticide-treated plants was only half of that observed on the susceptible cultivar. In 1992, under abnormally wet, cool conditions, squash bug densities were higher on insecticide-treated plants and lower on plants where parasitoids were released than in 1991. Fruit quality for both cultivars was substantially reduced in all treatments in 1992, The wet, cool conditions apparently had less of an effect on pest densities and fruit yields on resistant pumpkins than on susceptible pumpkins. The expected net income for insecticide-treated pumpkins was substantially lower in 1992 than in 1991. Where biological control and host plant resistance were combined, loss in expected net income in 1992 was considerably less than in 1991. Although costs associated with biological control were very high relative to the revenues, integrating biological control with host plant resistance may have some potential as an alternative management strategy.

A laboratory experiment was conducted to determine whether leaf exudates could be used as a source of adult nutrition for the squash bug, Auasa tristis (De Geer), egg parasitoid, Gryon pennsylvanicum (Ashmead), and to compare adult and progeny fitness traits when female Wasps were provided with squash leaves, a standard honey diet, a combination of leaves and honey, or water only Results showed that fecundity, progeny developmental rates, and progeny survival did not differ significantly when females were exposed to different dietary sources. Adult longevity was shorter on squash leaves without honey than on leaves with honey or the honey–only diet. However, reproductive fitness was not reduced because oviposition had been completed before death of the adult females. When only water was provided, parasitoid females lived only a few days. Observations showed that squash leaves have two kinds of trichomes (hair–like and peg–like), both of which produce droplets that are fed on by both sexes of G. pennsylvanicum. Nutrient analyses revealed that exudates from the hair–like trichomes are composed predominantly of monosaccharides (mainly glucose and galactose), and that the peg–like trichomes produce glucose and some protein. Thus, these trichomes appear to serve as extrafloral nectaries and may provide an important energy source for augmentatively released G. pennsylvanicum .

Adult squash bugs, Anasa tristis (De Geer), were confined on seedling watermelon plants at densities of zero, one, two, and four per plant. Squash bugs were allowed to feed on the plants until plants died or reached 30 cm in height. Number of leaves and length of plant vine were recorded at 2- or 3-d intervals. Seedling foliage, stems, and roots were harvested and dried after plants reached 30 cm in height. Growth of seedlings was regressed on number of squash bugs and results indicated that an increasing density of squash bugs feeding on seedlings resulted in a significant reduction in plant growth. Additionally, increased density of squash bugs resulted in reduced weight of foliage and root dry biomass. Seedling mortality increased as the density of squash bugs increased.

Reproductive phases, fecundity, and adult longevity of the squash bug, Anasa tristis (De Geer), were determined under laboratory conditions at a constant temperature of 26.7°C for five cucurbit hosts. Squash bugs on muskmelon, Cucumis melo L. ‘Hales Best #36’, had the longest premating phase. The preoviposition phase was shorter and the oviposition phase was longer on two cultivars of Cucurbita pepo L., yellow straightneck ‘Hyrific’ squash and ‘Jack O'Lantern’ pumpkin, than on watermelon, Citrullus lanatus (Thunberg) Matsumura and Nakai ‘Crimson Sweet’, and muskmelon. Females had the longest postoviposition phase on watermelon. The highest fecundity was observed on pumpkin seedlings. Host type did not affect egg mass size, egg hatch, percent hatch, or egg development. Higher percentages of egg masses were oviposited on the abaxial leaf surface than other plant locations on all hosts. Male squash bugs lived longer on pumpkin, squash, and watermelon than on muskmelon and cucumber, Cucumis sativus L. ‘Poinsett’, whereas females lived longer on pumpkin than on squash, muskmelon, and cucumber. Males lived longer than females on pumpkin and squash. The different host effects on reproduction, fecundity, and longevity indicate that host type is important when developing control strategies for the squash bug.

The plant tissues ingested by Anasa tristis (DeGeer) (Heteroptera: Coreidae) and the wilting of Cucurbita pepo L. (Cucurbitaceae) caused by A. tristis were investigated by feeding and light microscopy studies. Anasa tristis ingests both cell contents and xylem. Wilting of leaves and young plants by A. tristis is due to the interruption of all xylem transport to the plant apical to the feeding site. Xylem transport is interrupted by blockage of xylem vessels with salivary secretions or severing of xylem vessels by A. tristis stylets. Restricting feeding sites by caging demonstrates that squash bug does not produce a toxin that is responsible for wilting.

Laboratory experiments were conducted to quantify effects of resistant and susceptible host plants on the preimaginal and adult biologies of the squash bug, Anasa tristis (De Geer), and its egg parasitoid, Gryon pennsylvanicum (Ashmead). ‘Early Prolific Straightneck’ squash, ‘Green Striped Cushaw’ pumpkin, and ‘Waltham Butternut’ squash served as test plants. Preimaginal development of the squash bug (egg to adult) was similar on all three cultivars (range: 31–35 d). However, survivorship to the adult was significantly lower on ‘Green Striped Cushaw’ and ‘Waltham Butternut’ than on ‘Early Prolific Straightneck’. Statistical differences in survivorship were not observed in second-generation squash bugs, suggesting that some selection may have occurred. Squash bug reproduction and longevity were similar on all three cultivars. However, the reduced juvenile survivorship on ‘Green Striped Cushaw’ and ‘Waltham Butternut’ resulted in significantly lower rmax values on these cultivars than on the more susceptible ‘Early Prolific Straightneck’. The dietary history of adult squash bugs did not significantly affect development, preimaginal survival, or reproduction of G. pennsylvanicum . However, adult longevity of the parasitoid was significantly reduced when its larvae developed in eggs of squash bugs that were reared on the most resistant cultivar (‘Waltham Butternut’).

An investigation to delimit the influence of feeding by adult squash bug, Anasa tristis (De Geer), on squash, Cucurbita pepo var. melopepo L. ‘Hyrific’, was done during the summers of 1988 and 1989. When two or more adult squash bugs were allowed to feed on plants at the two-leaf stage for 200 DD (base 15.6°C), yield reductions were caused primarily by seedling mortality. Plants surviving the infestation period were typically unable to make up for growth delays induced by squash bug feeding. The size of the plants at infestation influenced yield, with four-leaf plants producing lower yields at maturity than those with six leaves.

A laboratory study was conducted to quantify the relationship of adult squash bug, Anasa tristis (DeGeer), density to summer squash ( Cucurbita pepo L. var Hyrific) plant damage. This relationship was investigated at five temperatures (20.0, 22.5, 25.0, 27.5, and 30.O°C) and four adult squash bug densities (none, two, four, and six). Vegetative growth rates and ovulate flower productivity decreased with increasing squash bug density; staminate flower productivity was not significantly affected by squash bug density. Growth rates and ovulate and staminate flower productivity increased with increasing temperatures. Squash bug mortality was highest at 25.0°C and lowest at 22.5°C. Female squash bug mortality was significantly higher when there were only two squash bugs per plant. The number of mean eggs per female increased with temperature and was unaffected by squash bug density.

Mated, 1-d-old female Gryon pennsylvanicum (Ashmead) exhibit a diel pattern of activity and rest. Daily activity (e.g., oviposition, walking, grooming, flying, feeding) is greatest during morning hours (0815-1215 hours CST). Two forms of resting behavior occur. “Motionless” is a temporary state occurring mostly during afternoon hours. The more pronounced resting phase, “tucking,” occurs in aggregated individuals of both sexes and is a form of rest previously undescribed in the parasitic Hymenoptera. The period of tucking persists from before lights go off to about 1 h after the lights go on. In individual wasps, activity resumes abruptly at about 0830 hours; by 0930 hours, all adults become active. Observations of a field population show a similar pattern of diel activity. The significance of these data for biological control programs is discussed.

Within-plant distribution of squash bug, Anasa tristis (De Geer), adults and egg masses on spring plantings of summer squash was determined by making whole-plant visual examinations. A significantly greater percentage of adults was found on the soil surface than on plants in early stages of crop phenology ( 90% of squash bug oviposition occurred on abaxial leaf surfaces. A significantly greater percentage (90%)of egg masses was deposited on leaves in the lower one-half of plants during vegetative plant growth. Average weighted mean egg mass location on plants was found to be highly correlated ( P < 0.01) with the number of leaves per plant. Results of this study suggest that sampling procedures should be developed separately for adults and egg masses. Monitoring for adults should include examination of both the plant and soil surface, whereas sampling for egg masses should concentrate primarily on the lower foliar canopy.

The effect of summer squash ( Cucurbita pepo L. cv. Hyrific) planting dates on the seasonal abundance of squash bug, Anasa tristis (De Geer), populations and fruit yields was investigated. Colonization by overwintered adult squash bugs was directly influenced by planting date. Significantly higher adult population densities developed on older, larger plants containing higher numbers of leaves than on younger plants with fewer leaves. As a result of adult preference for larger plants, egg mass and nymphal populations were significantly more abundant on early-planted squash. Mean numbers of squash bugs per leaf were correlated ( P < 0.05) with mean number of leaves per plant, suggesting that plant size may influence host plant selection. Regardless of planting date, squash bugs were most abundant on plants during flowering and fruit set. Manipulation of squash plantings may be a means of managing overwintered squash bug populations in spring crops to avoid yield losses.

Probing behaviors of first-instar squash bugs, Anasa tristis (De Geer), were electronically monitored and net weight gains of nymphs were determined on leaves of cucurbit hosts in the genera Cucurbita, Citrullus , and Cucumis . Force required to puncture cucurbit leaves was also examined. Squash bugs monitored for ≈8 h produced three waveforms (Wa, Wb, and We) on which comparisons could be made. We was the dominant waveform on all hosts. Histological examinations of squash bug salivary sheaths in leaf tissues taken during We revealed that the sheath tips were located in vascular bundles. Among hosts, differences were seen in mean probing duration per probe and in the waveform durations per probe for Wa and Wb. Net weight gains of squash bug nymphs were not different among hosts. Although leaf hardness was significantly different among hosts, it was not definitively determined to be a factor affecting squash bug feeding.

The occurrence of squash bug, Anasa tristis (DeGeer) on yellow summer squash grown under different cultural systems was studied in one experiment in 1987 and two experiments in 1988. The influence of row covers-black plastic and aluminized mulch-on the occurrence of squash bug was evaluated. Mulch production systems (black plastic or reflective) harbored more squash bugs than bare ground in 1987 studies. No differences in the density of squash bug were detected in plots with aluminum mulch (paper-backed) compared with either white plastic or aluminized black plastic. Early in both 1988 studies, significantly more squash bugs were observed in plots with aluminum mulch compared with those with black plastic. As plant development progressed, differences in squash bug numbers between the two mulch types decreased. However, squash grown in mulched plots, regardless of the type of mulch used, had consistently larger squash bug populations than those grown in bare ground. Row covers delayed squash bug colonization but when the covers were removed to allow plant pollination, squash bug colonized quickly. Mulch covers, regardless of type, provide a harborage for squash bug adults and nymphs. Greater numbers of squash bugs in mulched culture systems may result in increases in squash bug control costs, which could offset any production benefit gained by mulch systems.

Six squash cultivars, Cucurbita spp., were evaluated in the field during 1983 and 1984, and five cucurbit hosts were evaluated during 1985 for ovipositional preference by squash bugs, Anasa Tristis (De Geer). Yellow straightneck ‘Hyrific’ and crookneck squashes were found to be the most preferred in the squash study. In the cucurbit study, two cultivars of C. pepo L., yellow straightneck ‘Hyrific’ squash and ‘Jack o’ Lantern’ pumpkin, were most preferred. Relatively few egg masses were found on watermelon, Citrullus lanatus (Thunberg) Matsumura & Nakai ‘Crimson Sweet’; muskmelon, Cucumis mela L. ‘Hales Best #36’; and cucumber, Cucumis sativus L. ‘Poinsett.’ The abaxial leaf surfaces of all hosts in both studies were the favored ovipositional site of squash bugs. This phenomenon is important in developing squash bug sampling strategies and in insecticide applications.

The squash bug, Anasa tristis DeGeer (Heteroptera: Coreidae), is a major pest of cultivated cucurbits in much of North America. Its seasonal population dynamics are determined in large part by the early season phenological adaptations of the overwintered adults. Squash bugs were maintained on pumpkin, Cucurbita moschata Duchesne (Cucurbitaceae), seedlings. Factors influencing the termination of diapause in squash bugs were studied. Squash bugs transferred from outdoors to long-day conditions during their prediapause period in October (when the respiratory rate declines to diapause levels) required longer to terminate diapause than squash bugs transferred in the winter after the prediapause period was completed. Females did not oviposit after up to 150 days in short-day conditions. Squash bugs maintained outdoors under natural photoperiods remained in diapause until at least late April. Food was shown to be necessary for the prompt termination of diapause. Resume Influence de la photoperiode et de l'alimentation sur l'achevement de la diapause de Anasa tristis A. tristis (Heteropt.: Coreidae) est un ravageur important des cucurbitacees dans une grande partie de l'Amerique du Nord, particulierement de Cucurbita spp. Les evenements phenologiques du debut de la saison conditionnent la dynamique de population pour la saison entiere. Cette etude concerne l'influence de la photoperiode et de l'alimentation dans l'achevement de la diapause. Les adultes ont ete maintenus sur des plantules de Cucurbita moschata Duchesne (var. Libbey's Select). La diapause etait etablie par la mesure du taux respiratoire et par l'absence de ponte. Ladiapause etait surveillee chez des insectes maintenus a l'exterieur en conditions naturelles, leurs taux respiratoires se maintenaient au taux correspondant a la diapause jusqu'a la fin avril au moins. Places apres novembre en jours longs et a 25 °C, la diapause s'interrompait rapidement. Ceux transferes en jours longs plus tot ont interrompu leur diapause mais ont demande plus de temps pour reagir au changement de photoperiode. Transferes a 25 °C mais en jours courts, leur diapause n'etait pas interrompue jusqu'a la fin de l'experience 150 jours plus tard. L'alimentation est necessaire pour une interruption rapide de la diapause en jours longs. L'alimentation associee a des jours longs ou croissants semble necessaire a l'achevement de la diapause de A. tristis dans les conditions naturelles.

The squash bug, Anasa tristis DeGeer, undergoes a reproductive diapause from late summer to spring in northeastern Kansas. In the laboratory, diapause was induced in 100% of adult females reared under photoperiods shorter than 14:10 (L:D) and in a variably lower percentage of the population under all longer photoperiods. The critical photoperiod for diapause induction falls between 14:10 and 14.5:9.5; this range compares closely with prevailing natural daylengths when 50% of the adult population enters diapause in the field. Between October and March, short daylengths maintained, and long daylengths terminated, diapause in field-sampled adults. Under natural daylength at 26°C, the duration of diapause became progressively shorter with advancing sample date. In nature, the photoperiodic maintenance of diapause is completed in most of the population by late May. A prolonged diapause probably serves to prevent premature postdiapause development during the thermally variable spring conditions encountered in Kansas. Some implications of these findings for biological control and pest management programs are discussed.

Laboratory investigations of the gregarious squash bug egg parasitoids Ooencyrtus anasae (Ashmead) and O . sp. were conducted at 20.8, 23.0, and 26.6°C. Females of both species emerged with undeveloped ovaries. Oocyte development proceeded during the preovipositional period (ca. 35 h at 26.6°C) but did not exceed half of the total fecundity at initial oviposition. Preovipositional periods, time to peak oviposition, and time to 75% oviposition were generally similar for both parasitoids at 20.8°C. However, reproductive responses differed at temperatures above 20.8°C. In O. anasae , oviposition occurred significantly earlier, and at a similarly higher rate, at 23.0 and 26.6°C than at 20.8°C, whereas significant changes in preovipositional and ovipositional biology of O . sp. occurred only after an increase from 23.0 to 26.6°C. O . sp. had a significantly higher fecundity and longer ovipositional period at each temperature than did O. anasae. Mean fecundities did not change significantly with increasing temperature. Both parasitoids had an unusually long postreproductive period (ca. 1 mo) and a longevity of 40 to 50 d. At 26.6°C, O . sp. had higher gross and net reproductive rates than O. anasae. However, O. anasae had a shorter generation time (21.4 versus 23.8 d) and higher innate capacity for increase (0.146 versus 0.134).

Squash bugs, Anasa tristis DeGeer (Heteroptera: Coreidae), overwinter as adults in reproductive diapause. To study factors influencing the induction of diapause, nymphs and adults were reared on pumpkin, Cucurbita moschata Duchesne (Cucurbitaceae), in the laboratory and field. Respiratory rates in diapausing adults were less than half the rate of non-diapausing adults. Short daylengths induced diapause in immature and mature adults, and as overwintered adults that had completed diapause. Oviposition by new and overwintered adult females ceased about 30 days after the onset of diapause-inducing conditions. No evidence of a period of insensitivity to photoperiod after the completion of diapause was found. The critical photoperiod for induction of diapause depended on temperature and on the stage of development at which experimental photoperiods were introduced. Incidence of diapause in adult females increased as bugs were transferred to experimental photoperiods as new adults, 5th-, and 4th-instars. Diapause induction in the field in central Illinois (latitude 40 °N) occurs during the first week in August, resulting in only a small partial second-generation. Resume Induction photoperiodique de la diapause chez Anasa tristis A. tristis est un ravageur important des cucurbitacees en Amerique du Nord, particulierement de Cucurbita sp. Cette punaise hiverne avec une diapause reproductive des adultes. Dans le centre de l'Illinois (latitude 40 °N), il y a chaque ete une generation complete et une generation partielle. L'etude a porte sur les facteurs endogenes et ecologiques influencant l'induction de la diapause. Des larves et des adultes ont ete eleves sur pousses de Cucurbita moschata en conditions naturelles et de laboratoire. Au laboratoire, la photoperiode critique dependait du stade de developpement des punaises lors de l'introduction des photoperiodes experimentales. A 27 °C, la photoperiode critique des punaises transferees de jours longs en conditions experimentales a ete: environ 14,8 L/9,2 D lorsque le transfert a eu lieu au 5eme stade; et environ 14,3 L/9,7 D pour un transfert comme jeunes adultes. La temperature influe aussi sur la photoperiode critique. A 21 °C, pour le 5eme stade la photoperiode critique a ete environ 15,5 L/8,5 D. Les larves, les adultes immatures et murs, ainsi que les adultes apres hibernation ont ete sensibles a la photoperiode. Les femelles mures cessent de pondre dans les 30 jours suivant l'introduction des conditions induisant la diapause. Rien ne laisse supposer la presence d'une periode d'insensibilite a la photoperiode apres la fin de la diapause.

Herbivore densities, weed composition and abundance, and crop yields per land unit were compared between squash monocultures and traditional maize/legume/ squash polycultures in tropical Mexico. The most abundant insect pest in the system, Diaphania hyalinata (L.) (Lepidoptera: Pyralidae), generally had lower population densities in polycultures than in monocultures. The squash bug, Anasa tristis (De Geer) (Heteroptera: Coreidae), tended to be more common in polycultures. Reasons for the observed patterns of squash herbivore densities are discussed in terms of the “resource concentration” hypothesis. Weed height and biomass were significantly greater in monoculture and, although yields of each component crop were decreased, total crop yields were higher in polycultures when estimated as a land equivalent ratio.

The population dynamics of the squash bug, Anasa tristis (DeGeer), and the seasonal development of the squash plant, Cucurmta pepo L. variety ‘Hyrific,’ were monitored during 1984 and 1985. Numbers of squash bugs increased dramatically throughout the season. Overwintered adults and subsequent oviposition occurred soon after plant emergence. The development of first-generation nymphs and adults slowly increased the total number of squash bugs in the field. The development of a second generation caused a pronounced increase in the total numbers present. The numbers of nymphs, adults, and eggs in the field increased at an exponential rate beginning about Julian date 192 (10 July). Late in the season the rate of oviposition decreased. Squash bugs complete two to three generations per year in Oklahoma. Our data suggest that early-season control of squash bugs is essential to prevent high densities of insects from occurring late in the year. Mean plant leaf area and the number of leaves followed a sigmoid-shaped growth curve, increasing slowly early in the season, becoming faster through midseason, and slowing again late in the season. The numbers of flower buds, flowers, and immature and mature fruit also followed a sigmoid-shaped growth curve throughout the season.

Phytophagous insect associations with 5 cultivated and 14 mesophytic and xerophytic wild Cucurbita spp. were recorded for 4 consecutive years. Overwintering striped cucumber beetles, Acalymma vittata (Fab.) were most attracted to the young growth of the Maxima and Ficifolia groups and the wild xerophytic Digitata group. Foliage feeding responses were strongest on the latter group. The spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber, exhibited a high affinity for the Maxima, the wild Lundelliana and Digitata groups. The squash vine borer severly injured the Maxima and Pepo groups. The squash bug, Anasa tristis (DeGeer), showed a high ovipositional preference for the Maxima and Mixta groups and a low preference for all other groups. All Cucurbita spp. were poor hosts for the melon aphid, Aphis gossypii (Glover), with the wild Sororia and Ficifolia groups most suitable for reproduction. The potato leafhopper, Empoasca fabae (Harris), preferred cultivated species but oviposited on all wild species except C. foetidissima (HBK). The potato aphid, Macrosiphum euphorbiae (Thomas), preferred the Sororia and Pepo groups. Principle component analysis revealed that the striped cucumber beetle, squash vine borer and the squash bug showed similar host preference patterns with the Maxima group being the most favored.

Laboratory investigations of the gregarious squash bug egg parasitoids Ooencyrtus anasae and O . n. sp. near anasae ( O . sp.) were conducted at 20.8, 23.0, and 26.6°C. In both species, total developmental periods (egg to eclosed adult) were inversely related to temperature. Temperature had no significant influence on survivorship, progeny production, or sex ratio. At each temperature, O. anasae developed and emerged about a day earlier and produced a significantly higher percentage of female progeny (77%) than did O . sp. (60%). Both parasitoids deposited an average of three (2–7) progeny per host. However, O. anasae consistently deposited more female eggs per host than did O . sp. Proportion of females produced per host by O. anasae tended to increase directly with number of hosts parasitized, but no such relationship was observed in O . sp. Total preimaginal survivorship in both parasitoids was about 89%. In O . sp., male progeny that developed without females emerged about a day later at all temperatures and had a lower pharate adult survivorship than did males that developed in hosts with female siblings.

A recent paper by Wigglesworth (1943) has dealt extensively with the metabolism of hemoglobin by certain blood-sucking Hemiptera and other insects. The data presented were of great interest from the standpoint of comparative biochemistry and aroused the writer's curiosity regarding the possible metabolic breakdown of the related pyrrole pigment, chlorophyll, by plant-feeding Hemiptera.

1. For species of insects that deposit their eggs on foliage, as Leptinotarsa decemlineata, Crioceris asparagi, and Anasa tristis, the rates of metabolism as measured by the CO2 output or the oxygen intake indicate, during embryonic development, a short formative period, followed by a very active extended growth. Those species that deposit their eggs in the soil, as Cotinis nitida and Popillia japonica, show that the formative period is greatly extended and the growth period similarly lengthened. 2. It has been shown from metabolism experiments that intensive histolysis occurs during the prepupal period and becomes less intensive during pupal development. 3. Metabolism experiments show a greater amount of energy change during embryonic development as compared to the energy developed during metamorphosis. This is shown by the greater CO2 output and by the oxygen intake. 4. Low respiratory quotients, varying from 0.42 to 0.71, have been obtained during the embryonic and pupal development of insects, resembling similar low quotients obtained with hibernating forms. 5. Changes from a neutral to an acid reaction (pH 6.8 to 5.9) have been observed to take place in some species during prepupal and early pupal development. As metamorphosis is completed a converse change occurs (pH 5.9 to 6.8). Changes in pH from an acid to neutral reaction were also observed to take place in some species, as Cotinis nitida and Hylemyia cilicrura, during embryonic development.

Greenhouse studies involving interactions of six varieties of Cucurbita spp. and the squash bug, Anasa tristis (De Geer) (Corei dae, Hemiptera), indicate that Butternut is the most resistant and Black Zucchini is the most susceptible of the group. A smaller amount of plant sap was removed from the more resistant plants. Lack of preference appeared to be the major factor involved in resistance. However, the resistant plants produced an antibiotic effect on nymphal development. Nymphs reared on Black Zucchini and Pink Banana attained a significantly later instar and lived longer than those reared on the other four varieties. Tolerance did not seem to be involved in the greenhouse studies. The order of resistance of the six varieties from high to low was Butternut, Royal Acorn, Sweet Cheese, Green Striped Cushaw, Pink Banana and Black Zucchini.

The squash bug, Anasa tristis DeG., has been a desirable subject for one whose interests are with the Hemipterous forms. Specimens used in the following studies were collected in early Octoher and were kept in a moderately cool basement room in a Riley insect cage. They were fed squash of the Acorn variety from a supply in storage and remained active throughout the fall and well into the winter.

In writing this article the chief aim is to endeavor to supply a reference work on the external morphological characters of a typical Heteropterous insect. For this reason the common squash bug has been selected as it is widely distributed, well known as a pest, and is readily obtainable for study.

The influence of five cucurbit hosts on survival, developmental time, and adult weight of the squash bug, Anasa tristis (De Geer), was determined. Percentage survival from egg to adult was significantly affected by host. Survival to the adult stage on the five hosts was highest on pumpkin, Cucurbita pepo L. var. pepo (70.0%), followed by squash, Cucurbita pepo L. var. melopepo (49.0%); watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai (14.4%); cucumber, Cucumis sativus L. (0.3%); and muskmelon, Cucumis melo L. (0%). Host type had a significant effect on developmental time to third and fifth instar and to adult, with a longer developmental time on watermelon. The adult sex ratio was 1:1. Adult females were significantly heavier than males. Greater adult weights for both males and females resulted when insects developed on squash. However, the effect of host on adult weight was significant only for males.

To obtain more information on arrestants and feeding stimulants for insects in general, and the boll weevil, Anthonomus grandis Boheman, in particular, tests with water extracts obtained from several plants were conducted at the Boll Weevil Research Laboratory during the summer of 1963. Four species of insects in addition to the boll weevil became numerous enough in the vicinity of the laboratory for such studies. The insects and plants used in the studies were: Monarch butterfly, Danaus plexippus (L.), on milkweed (Asclepias syriaca L.) ; elm leaf beetle, Galerucella xanthomelaena (Schiffermuller), on American elm (Ulmus americanam . L) ; a species of Gastrophysa on dock (Rumex obtusifolius L.) ; the squash bug Anasa tristis (De Geer), on pumpkin (Cucurbita pepo L.); and the boll weevil, on cotton squares (Gossypiuin hirsutum L.).

The junior author was assigned a study of the transformation of the spermatids into spermatozoa in living Anasa. He was not told that fixed material had been used for such a study of the squash bug. Thus this study became a test of just what can be seen in living material. After making the drawings and writing the descriptions the junior author compared his findings with those recorded in literature. Most of the observations are those of the junior author.