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The leafhopper Sophonia rufofascia (Kuoh & Kuoh) is a recent invasive pest attacking a wide variety of plant species in Hawaii. We surveyed the distribution and parasitism of its eggs in a number of natural and agricultural habitats on the islands of Kauai, Oahu, and Hawaii. Egg density was fairly low, with egg distribution affected both by plant species and plant habitat. Approximately 40% of S. rufofascia eggs, averaged over all plants and sites, were parasitized by Chaetomymar sp. nr. bagichi Narayanan, Subba Rao, & Kaur; Schizophragma bicolor (Dozier); and Polynema sp. Haliday (Hymenoptera: Mymaridae). Percentage parasitism varied widely among different plant species and habitats. C. sp. nr. bagichi was the most abundant and widely distributed species, but the parasitoid guild varied depending on plant and on habitat. The implications of these results on decisions regarding classical biological control of twospotted leafhopper in Hawaii are discussed.

Colorado potato beetle dispersal and reproduction was investigated under field and laboratory conditions. Movement and mating of newly emerged summer-generation Colorado potato beetle adults was monitored in the field using a mark-recapture technique, and beetle mating within experimental plots was recorded. The number of degree-days (DD) required for the beetles to become reproductive was tested in an environmental chamber using 10°C as a developmental threshold. A computer-linked flight mill system was used to quantify the influence of mating on the flight behavior of male and female beetles. Adult dispersal started within the first 24 h after eclosion from the pupae, but a significant proportion of newly emerged beetles stayed close to the place of their larval development until reaching reproductive maturity. The beetles required at least 34 DD before mating produced viable offspring, and females did not start laying eggs until a minimum of 51 DD after eclosion. Mating had a pronounced effect on beetle flight, decreasing flight activity of the females and increasing flight activity of the males. Enhancing gene flow between beetles surviving on transgenic plants and susceptible beetles in refugia should be advantageous in managing beetle resistance to transgenic plants.

Laboratory experiments were conducted to compare relative fitness of strains of Colorado potato beetle resistant and susceptible to Bacillus thuringiensis subsp. tenebrionis Cry3A toxin. Net replacement rates and intrinsic rates of population increase were calculated for resistant and susceptible populations. During the experiment, susceptible males on average copulated 13.3 6 1.5 times, whereas resistant males copulated only 8.0 6 1.0 times. Susceptible females produced an average of 824.2 6 68.1 eggs and 590.9 6 58.5 larvae, which was significantly .484.6 6 48.0 eggs and 334.9 6 39.7 larvae produced by an average resistant female. As a result, both net replacement rate and intrinsic rate of increase were reduced for the resistant population. Furthermore, twice as many susceptible beetles as resistant beetles survived overwintering diapause. Our results clearly indicate that relative fitness of resistant individuals is reduced in the absence of B. thuringiensis in the environment. Therefore, relaxation of selection pressure through refugia and insecticide rotation will favor decrease in the frequency of resistant alleles in beetle populations.

Sperm precedence in the Colorado potato beetle, Leptinotarsa decemlineata (Say), was investigated using phosphoglucomutase (Pgm) allozymes as genetic markers. Females were mated to 2 males carrying different Pgm alleles, and the proportion of offspring sired by each male was determined by cellulose acetate gel electrophoresis. Our results indicate that Pgm alleles in the Colorado potato beetle are inherited in the Mendelian fashion, and there is no change in sperm utilization over time. We also were able to confirm that sperm precedence in this insect is incomplete, with approximately equal to 72% of the larvae fathered by males at the 2nd mating. Possible implications of incomplete sperm precedence for insecticide resistance management are discussed.

Adults of full-sib Colorado potato beetle families were separated into 3 groups fed on different diets: transgenic potato foliage, potato foliage treated with a foliar formulation of B. thuringiensis endotoxin (12.37 μg of Cry3A δ-endotoxin per 1 μl of mixture), and untreated potato foliage. After feeding for 3 h, all the beetles were placed on a computer-linked flight mill system. The number of beetles that flew, duration of each flight, and the number of flights for each beetle were recorded. Feeding on transgenic foliage had a strong negative effect on the proportion of beetles that flew, as well as the average number of flights per flying beetle. Mean flight duration was not influenced by the beetle diet, but interaction between family and diet was highly significant, with pronounced family effects observed for the beetles fed on standard and treated foliage. Beetles from families that performed the longest flights when fed on untreated foliage performed the shortest flights when fed on transgenic foliage. Suppression of beetle flight as a result of endotoxin ingestion could keep beetles within transgenic fields, thus increasing selection pressure toward development of physiological resistance. One possible way to reduce this pressure is to provide refugia for susceptible beetles in close association with fields planted to transgenic potato.

The two-spotted leafhopper, Sophonia rufofascia (Kuoh and Kuoh), is an exotic pest from South-East Asia that attacks a wide variety of plant species in Hawaii. Myrica faya Aiton is an aggressive exotic weed that displaces and excludes native plants in Hawaiian forests. It has been argued that because of the high nutritional quality of its foliage, M. faya might facilitate leafhopper invasion of native Hawaiian ecosystems that were originally dominated by the endemic tree Metrosideros polymorpha (Gaudichaud). In the present study, we quantified suitability of M. faya and M. polymorpha as ovipositional hosts for S. rufofascia. Overall, leafhoppers preferred to deposit their eggs into the foliage of M. faya. M. faya presence in the area did not affect leafhopper oviposition on M. polymorpha. Foliar pubescence provided good protection of hirsute morphotypes of M. polymorpha. At the same time, glabrous M. polymorpha morphotypes were quite suitable for leafhopper oviposition. There was no difference in the abundance of leafhopper eggs along a precipitation gradient. Our results confirm that invasion of native Hawaiian forests by the weed M. faya will facilitate their invasion by S. rufofascia. Because of the broad host range characteristic of the two-spotted leafhopper, this build-up may adversely affect a number of endemic plant species growing in native forests.