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Leaf-cutting ants live in symbiosis with the fungus Leucoagaricus gongylophorus (Singer) Moller that grows in their nests. This fungus is the main nutritional source for these ants that provide conditions for its development. Although plant extracts of Ageratum conyzoides L., Coriandrum sativum L. and Mentha piperita L. are known to cause mortality in ants in the laboratory, their effects on L. gongylophorus are still unknown. The aim of the present study was to determine the effects of the A. conyzoides , C. sativum and M. piperita extracts on L. gongylophorus . The biomass of the fungus grown by the leaf-cutting ants was assessed in culture medium with three concentrations (25, 50, and 100 mg/mL) of A. conyzoides , C. sativum and M. piperita extracts. The results showed that all the three extracts inhibited the growth of L. gongylophorus . At concentrations of 25, 50, and 100 mg/mL, the A. conyzoides extract exhibited 81, 93, and 100% reduction in the fungal biomass; the C. sativum extract showed 23, 27, and 100% reduction in the fungal biomass; and the M. piperita extract demonstrated 96, 99, and 100% reduction in the fungal biomass, respectively. Furthermore, the secondary metabolic compounds of these plants were found to have fungistatic and fungicidal properties, similar to that observed in other fungal species. In conclusion, the extracts of A. conyzoides , C. sativum and M. piperita inhibited the growth of L. gongylophorus in the laboratory, and should be further studied for their potential use in baits to control leaf-cutting ants.

Social insects can live in densely populated colonies where mortality risks are increased by inter-individual transmission of pathogens. Thus, diverse strategies are employed against such infection risks, including the display of sophisticated behavioural traits. Considering that the waste of the leaf-cutting ant contains pathogens, worker ants that tend the fungus garden – here called fungus garden workers – should exhibit avoidance behaviour toward midden workers to minimize contamination of the fungus garden. We studied the behaviour of garden workers when confronted with midden and forager workers in colonies of Atta sexdens (Linnaeus, 1758). Eight colonies were used: in four colonies, the midden was inoculated with spores of the weed fungus Escovopsis weberi (Muchovej and Della Lucia, 1990), and in the other four colonies there was no artificial contamination. Grooming, self-grooming, inspection, immobilization and aggression behaviours were quantified. Additionally, we checked for fungal con...

Development of insecticide resistance is a serious worldwide challenge for pest management of stored-product insects, as recognized since the FAO Global Survey of the mid-1970s. In this study, we carried out a survey of physiological and behavioral resistance to two organophosphate insecticides (chlorpyrifos-methyl and fenitrothion) in 14 populations of Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) from Brazil and one from Paraguay and investigated if differences in population growth, body size, and respiration rate were associated with the resistance. Concentration-mortality bioassays were carried out and behavioral resistance was studied by recording the walking behavior on filter-paper half-treated with insecticide and determining the distance walked, walking velocity, resting time, and time spent on the treated side of the arena. The instantaneous rate of population growth (ri) was determined, and so were maize consumption, insect body mass, and insect respiration rate. Only low levels of resistance were detected to chlorpyrifos-methyl (≤6.1-fold) and fenitrothion (≤7.7-fold). The walking behavior on treated surfaces varied among the populations, but no repellence was detected and no significant correlation was observed between the level of organophosphate resistance and the mobility parameters assessed. Population growth and respiration rate were similar among the populations although there were differences in food consumption and insect body mass. The results of this study indicate that the levels of organophosphate resistance in Brazilian populations of maize weevil are low and not associated with fitness costs. No evidence of behavioral avoidance to organophosphates was observed.

Leaf-cutting ants live in symbiosis with a basidiomycete fungus that is exploited as a source of nutrients for ant larvae. Tests of brood transport revealed that Acromyrmex laticeps nigrosetosus workers did not discriminate a concolonial brood from an alien brood. The same result was observed with tests of fungus transport. Adult workers showed no aggressive behaviour to workers from other alien colonies (non-nestmates). There was no qualitative variation in the chemical profiles of larvae, pupae and adult workers from the different colonies. However, quantitative differences were observed between the different colonies. Hypotheses about the lack of intraspecific aggression in this subspecies of ants are discussed. As formigas cortadeiras vivem em simbiose com um fungo basidiomiceto que é utilizado como fonte de nutriente para suas larvas. Testes de transporte de prole revelaram que as operárias de Acromyrmex laticeps nigrosetosus não discriminaram a prole concolonial de prole estranha. O mesmo resultado foi verificado com testes de transporte do fungo. As operárias adultas não exibiram comportamento agressivo frente a operárias de outras colônias (não companheiras de ninho). Não houve variação qualitativa nos perfis químicos de larvas, pupas e operárias adultas de diferentes colônias. No entanto, diferenças quantitativas foram observadas entre as diferentes colônias. Hipóteses sobre a ausência de agressão intra-específica nesta subespécie de formiga são discutidas.

Leaf-cutting ants are highly polyphagous insects, but some plants escape their attack due to thepresence of secondary metabolites that are toxic to the ant–fungus symbiosis. Previous studies havedemonstrated that the terpenoid β -eudesmol extracted from Eucalyptus species (Myrtaceae) isresponsible for the deleterious behavior in colonies of leaf-cutting ant species. The objective of thisstudy was to evaluate the effect of β -eudesmol on workers of the leaf-cutting ant Atta sexdens rubro-pilosa Forel (Hymenoptera: Formicidae). This chemical caused behavioral modification in the colo-nies, leading to mutilation and death of workers. It is suggested that β -eudesmol interferes withcolony nestmate recognition. As a consequence, colony cohesion may be disrupted by β -eudesmol what could be used as an additional control tactic against this important pest ant. Introduction Leaf-cutting ants, as social insects, use recognition systemsto distinguish nestmates (Lenoir et al., 1999). This complexrecognition behavior is based on individual ant and colonyodor, and is indispensable for c olony maintenance (Crozier& Dix, 1979). These odors or cues are of a chemical nature,and are characteristic for each colony.Jutsum et al. (1979) demonstrated the importance ofenvironmental cues, such as leaf substrate, in the recogni-tion process. According to Jaffe (1983), the head is the bodypart where substances responsible for nestmate recogni-tion accumulate; the alarm pheromone, also produced inthe head, could be involved in the process. In

The present study was undertaken to assess the side-effects of chlorpyrifos on springtails, ants and oribatid mites associated with the soil surface of no-tillage cornfields in Brazil. Three 0.3 ha cornfields were divided into plots and, during tasseling, the plants in areas to be treated were sprayed twice with insecticide, with a 3 day interval. Pitfall traps were used to sample soil arthropods 1 week before and 1, 2, 3, 4, 5 and 8 weeks after spraying. Principal components analysis detected no negative effect of insecticide chlorpyrifos on the assemblage of soil arthropods. Nonetheless, the activity of the ant Solenopsis saevissima (Fr. Smith) was lower 2 weeks after spraying but recovered afterwards, while the frequency of Ectatomma brunneum Fr. Smith, was significantly reduced only at the third week after spraying, and did not show any recovery until the end of the study. Chlorpyrifos did not decrease the overall abundance of Collembola. However, it had a significant impact on the members of the orde...

Corn plants were twice sprayed at 3-day intervals during tasselling to evaluate the effect of chlorpyrifos on ear damage by H. zea and also on the populations of the natural enemies associated with this moth. The abundance of H. zea eggs and larvae and of predators on the whole plant, the egg parasitism by Trichogramma pretiosum Riley and the percentage of injured ears were sampled weekly. Chlorpyrifos did not show any significant effect on population levels and on ear damage by H. zea. Natural parasitism of eggs ranged from 52 to 75% and did not differ between treated and untreated plots; furthermore, the percentage of non viable eggs and adult emergence were not influenced by insecticide application. Among the predators found in the plots, Doru luteipes was not affected by spraying, whereas the abundance of Orius sp. decreased 21 days after insecticide application. The frequency of the ant Pheidole sp. was not affected by chlorpyrifos; however, foraging activity of Crematogaster sp. on treated plots was rapidly reduced and remained low during the following 2 weeks. The small number of damaged ears suggests that the insecticide did not affect the efficiency of the natural enemies of H. zea.

We assessed the response of maize canopy arthropods to the insecticide chlorpyrifos. Four 0.3 ha (18 2 180 m) plots were divided into two subplots, a control and a treated area. During tasseling of the plants, the treated area was sprayed twice, with an interval of 3 days. Ten plants were sampled: 1 day before spraying, and 7, 14, 21 and 28 days after spraying. The insecticide had no effect on insect herbivores: a high density of Spodoptera frugiperda larvae was present in the treated plots. A few predator arthropod species were negatively affected by the insecticide, but their numbers or activity increased 2 weeks after the treatment of the plots. A canonical variate analysis showed no pronounced effect of the insecticide on arthropod communities; the largest variations on species abundance were related to sampling occasion. These results can be explained by the combination of the short period of chlorpyrifos residual activity on the plant surface and the great potential for recolonization of the areas b...

The objective of this work was to study the effect of plant canopy height on the resistance of the tomato species Lycopersicon hirsutum to the tomato leafminer Tuta absoluta. Determination of the levels of tridecan-2-one (2-TD) and undecan-2-one (2-UD) in L. hirsutum, as well as the leaf area, density and types of trichomes present in L. hirsutum and L. esculentum were made on apical, medium and basal parts of plant canopy. Correlation of these data were made with the following biological characteristics of T. absoluta: rates of oviposition and egg hatching; length of egg, larval and pupal stages; mortality of the larval and pupal stages; pupal weight; and sex ratio. Levels of 2-TD on leaves of L. hirsutum increased from bottom to top of canopy. Tuta absoluta had higher oviposition and egg hatching, as well as lower mortalities and smaller larval and pupal periods in L. esculentum than in L. hirsutum. Longer pupal period and greater number of small and large mines of T. absoluta were verified in the apical and medium parts of L. hirsutum plants. On the other hand, higher pupal mortality and longer larval periods were obtained in the apical and basal parts of the L. hirsutum plants. Larval mortality was higher in the basal part of those plants. In L. esculentum, leaves from the apical part of the plant promoted lower mortality, longer larval period and greater number of large mines of T. absoluta. However, a shorter pupal period was verified on leaves of the basal part. It appears that an increase in glandular trichome density in L. hirsutum leads to an increase in the levels of 2-TD, which, in turn slows down larval development.

This work was conducted in corn fields in the silking stage, in Sete Lagoas, MG, (EMBRAPA/CNPMS). In one experiment, different numbers of virgin females of Helicoverpa zea were compared to a commercial synthetic pheromone formulation using a Pherocon 1C sticky trap from the USA. In another experiment, calling behavior and nocturnal activity of adults were observed during the fall, winter, summer and spring using virgin females. There were no significant differences in the adult catches, using one, three or five females/trap. Three females were considered the best number, taking in count that the use of five females/trap was impractical and there is the possibility of death or physiological malfunction of the female in case of the lowest density. There were no H. zea catches in traps with the synthetic pheromone which, instead, captured the noctuid Mythimna. Mating activity of H. zea started soon after the scotophase and the catching peak occurred after midnight. The field reproductive activity was related to ambiental temperature.

The first known long-range female-released sex pheromone for the family Cerambycidae is reported fromMigdolus fryanus, a sugarcane pest in South America. Although two female-specific compounds, namely, N-(2′S)-methylbutanoyl 2-methylbutylamine and N-formyll-isoleucine methyl esters were identified, field tests with synthetic chemicals revealed that only the amide was active and that the amino acid derivative neither increased or decreased trap catches by the amide. This is the first identification of amide as a sex pheromone.

The trail pheromone ofAcromyrmex subterraneus subterraneus consists simply of the heterocyclic ester methyl 4-methylpyrrole-2-carboxylate in the venom reservoir of workers at about 1.2 ng/ant. No pyrazines were detected, and no enhancement of trail-following was observed when pyrazines were added to the pyrrole compound.

Males of the sugarcane borer,Migdolus fryanus (Coleoptera: Cerambycidae), are attracted to females by means of a sex pheromone. Mating usually occurs during a few days from October to March under field conditions in São Paulo State, Brazil. This work reports on mating of this species as affected by daily climatic factors, during a single nuptial flight. Maximum male capture by the natural sex pheromone occurred from 10∶00 to 11∶00 AM at air and soil temperatures of 30.0°C and relative humidity of 57.0%. As these temperatures increased, females burrowed into the soil, as they are more sensitive to heat than males. Thus, it was concluded that sex pheromone-mediated mating in this cerambycid is directly affected by temperatures of air and soil.

The objective of this work was to study the effect of colony waste on the mortality of workers of Atta sexdens rubropilosa Forel colonies fed with different plant substrates. Eight nests were used; two colonies each were fed with Acalypha wilkesiana Müller.Arg, Ligustrum japonicum Thunb, Eucalyptus urophylla S.T. Blake or a mixture of the three substrates in equal proportions. Irrespective of diet, being kept with waste led to higher mortality. However, workers that were kept in contact with waste produced by colonies fed Acalypha had higher average survival rate and later death when compared with workers from the other treatments. Workers from the Eucalyptus-fed colonies had the lowest survival rate and 50% of them died within four days of exposure to Eucalyptus waste. Trichoderma viride Pers. ex Gray, a fungus garden antagonist, and the entomopathogen Aspergillus flavus Link. ex Gray were present in the colonies supplied with all plants. The largest fungus diversity was verified in the waste of colonies fed Acalypha and the mixture of Acalypha, Ligustrum and Eucalyptus. Therefore, antibiotic properties of Acalypha did not reduce contaminant diversity but apparently minimized effects of pathogenic microorganisms present in the waste such as Asp. flavus. This may explain the highest survival rate of workers in this treatment.

The basidiomycetes which are cultivated by ants are not well documented taxonomically owing to the lack of adequate specimens. Leucoagaricus weberi is described from a living nest of leaf cutting ants and compared with known species, and a new section Oleoagaricus, is proposed to accommodate species of Leucoagaricus which possess oleiferous hyphae.

Leaf-cutter ant species (Attaspp.) are key pests of cultivated crops in the Neotropics, and recent studies have demonstrated that workers ofAttaspp., particularly ofAtta sexdens rubropilosa, exhibit aggressive behavior among nestmates when in contact with the sesquiterpene β-eudesmol, found in leaves ofEucalyptus maculata. However, the underlying mechanism sparking this behavior pattern has yet to be investigated. This work aimed to elucidate the mechanism by which this substance elicits aggression in workers ofA. sexdens rubropilosa. The results, thus obtained, showed that β-eudesmol is able to modify the chemical composition of the workers cuticle, impairing nestmate recognition, triggering alarm behavior and leading to nestmate aggression.

The response of Atta sexdens rubropilosa Forel workers to essential oils, epicuticular wax and hexane, dichloromethane, ethyl acetate, and methanol extracts of Eucalyptus maculata was evaluated. Hexane extracts of E. maculata interfered with the recognition mechanism among workers. The main active compounds identified from this plant were the sesquiterpenes elemol and beta-eudesmol. These compounds may be responsible for the resistance of this species to ant attack.

A colony of Atta sexdens rubropilosa was studied in the presence and absence of the queen. The frequency of 23 previously defined behaviors was quantified in terms of average frequencies of act occurrence. Colony behavioral activities such as foraging, fungal care, and refuse manipulation were not directly influenced by the queen's presence up to 30 days after the queen's death. The queen, which also seems to maintain colony cohesion aside from reproduction, indirectly affected brood care.