The species of the genus Isonychia Eaton, 1871 (Isonychiidae) of East Palaearctic are revised. Two subgenera, Isonychia s.s. and Prionoides Kondratieff et Voshell, 1983, are represented in the Palaearctic. New species and subspecies of Isonychia s.s. are described: I. sexpetalasp. nov., I. ussurica sibiricasubsp. nov., I. concoloriasp. nov., I. crassiusculasp. nov., and I. vshivkovaesp. nov. with subspecies I. vshivkovae vshivkovae and I. vshivkovae sinitshenkovaesubsp. nov. A new species group japonica, with three species (I. crassiuscula, I. vshivkovae, and I. japonica), is recognized on the basis of adult and larval characteristics. The name Isonychia hainanensis She et You, 1988 is synonymized with Isonychia ignota (Walker, 1853) syn. nov.

Three new species of Tabanidae egg parasitoids are described: Telenomus hybomitraesp. nov. and Telenomus utilissp. nov., both reared from eggs of Hybomitra nitidifrons nuda (McDunnough) and Hybomitra lasiophthalma Macquart, and Telenomus chrysopsissp. nov., reared from eggs of Chrysops aestuans Wulp, Chrysops excitans Walker, and Chrysops mitis Osten Sacken. Specimens of these species were compared with type specimens of known New World species of scelionid parasitoids attacking tabanid eggs. Diagnostic characters and identification key to the Nearctic species are provided.

Microberotha macculloughigen. nov. and sp. nov. from Early Eocene Okanagan Highlands amber of Hat Creek, British Columbia, Canada, is described. This new genus and species represents one of the smallest members of the family Berothidae and the first occurrence of the family in the New World Tertiary. The systematic position of the genus Microberotha within the family is rather unclear, but the structure of the male genitalia indicates a close association with the subfamily Cyrenoberothinae. Stratigraphy and palaeoenvironment of the Hat Creek locality are briefly discussed.

The requirements for successful diapause of field-collected larvae and emergence of the adult wheat midge, Sitodiplosis mosellana (Géhin), and its egg parasitoid Macroglenes penetrans (Kirby) were investigated in the laboratory. Both species showed little decline in survival for up to 5 weeks at 20 °C in dry wheat spikes and could successfully diapause in wheat spikes at 0 °C for at least 200 d, although larvae usually drop to the soil to diapause. Both species diapaused successfully in clay loam and fine quartz sand, but survival was lower in vermiculite or coarse activated clay. Diapause was completed successfully at soil temperatures of −5 to 2.5 °C, and both species survived for at least 500 d at 2.5 °C with no increase in mortality. Larval survival declined after 120 d at −10 °C. Usually more than 95% of all surviving wheat midges emerged as adults after a single diapause period of 100 d or more, but up to 5% of wheat midges and 12%−57% of parasitoids did not emerge until they were exposed to a second cold period. Postdiapausal larvae pupated and adult wheat midges emerged at constant temperatures of 16, 20, 26, and 28 °C with no differences in mortality, although none emerged at 10 °C. The timing of wheat midge emergence was temperature dependent, requiring 306 degree-days above a threshold of 9 °C. Degree-day requirements and soil temperatures from a nearby weather station accurately predicted the average timing of emergence in the field, but not the year-to-year variation in date of 50% emergence. The wheat midge and its parasitoid are well adapted to the conditions they encounter in their range in western Canada. Methods for rearing both species through diapause and adult emergence are described.

Blackheaded fireworm (Rhopobota naevana (Hbn.)) mating can be disrupted by pheromone components released from spiral polyvinyl chloride (PVC) dispensers in large field plots on cranberry (Vaccinium macrocarpon (Aiton) (Ericaceae)) farms. The main pheromone component ((Z)-11-tetradecen-1-ol acetate (Z11-14:Ac)) or a blend similar to natural pheromone (Z11-14:Ac, (Z)-11-tetradecen-1-ol (Z11-14:OH), and (Z)-9-dodecen-1-ol acetate (Z9-12:Ac)) was released from PVC dispensers into 0.8-ha plots on cranberry farms. Regardless of the treatment, free-flying males in treatment plots located fewer than 5% of individually caged virgin females, whereas mate location in most control plots ranged from 14%–75%. Location of pheromone lures loaded with 1.0 mg of the three-component blend was reduced in both treatments, but not to the same extent as was location of females. The magnitude of mating disruption indicated by 0.01-mg lures was similar to that indicated by caged females. Estimated release rates from dispensers loaded with Z11-14:Ac alone were linear and similar in both years of the study, declining from 575–720 mg/ha per day to 175–220 mg/ha per day after 100 days. Three-component dispensers placed in the field in July 1994 showed a steeper decline in release rates of Z11-14:Ac and a change in component ratios from 6.2:2.5:1 to 8:2:1 (Z11-14:Ac: Z11-14:OH: Z9-12:Ac) over the 60-day release period. After one season of mating disruption, the number of eggs and the number of foliar samples with larval feeding shelters were not consistently reduced in treatment plots. Mated females may have dispersed into the plots and oviposited. PVC dispensers effectively disseminate pheromone for mating disruption but are labor-intensive to use. In the cranberry system, their use might be limited to research plots and isolated farms of <8 ha.

Flight of overwintered and summer population Colorado potato beetles, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), with a range of wing loadings was measured following exposure to different quality diets. Beetles fed a diet of insect-resistant foliage expressing Bacillus thuringiensis tenebrioniz toxins, beetles that did not feed but consumed water, and those that were starved without access to water exhibited a lower range of wing loadings than those fed conventional foliage, but there was no corresponding increase in flight frequency. Exposing potato beetles to poor food or no food resulted in a wing-loading range of 50–140 mg/cm2 compared with a range of 80–200 mg/cm2 for beetles fed conventional foliage. No flight was observed when wing loadings were less than 80 mg/cm2 of wing surface, presumably because of other physiological processes associated with poor nutrition and not because of wing loading per se. Overwintered and summer population beetles fed a diet of conventional potato foliage did not take off when wing loading exceeded 150 mg/cm2 of supporting wing surface. Similar trade-offs between flight capacity and consumption of large meals may exist for other insects.

Parasitoids of adult corn leafhoppers, Dalbulus maidis (DeLong et Wolcott), were studied in irrigated maize (Gramineae) growing during the dry season in Mexico. Dalbulus maidis was parasitized by Metadorylas spinosus (Hardy) (Diptera: Pipunculidae), Halictophagus naulti Kathirithamby et Moya-Raygoza (Strepsiptera: Halictophagidae), and Gonatopus bartletti Olmi (Hymenoptera: Dryinidae) at 24 of the 54 sites where D. maidis were collected. Greater rates of parasitism occurred at higher elevations (R2 = 0.41) and at more southern latitudes (R2 = −0.52). Metadorylas spinosus is a previously unreported parasitoid of D. maidis, and this is the first report of H. naulti parasitizing Dalbulus elimatus (Ball) and Dalbulus gelbus DeLong. Gonatopus bartletti has the broadest geographic and temporal distribution of the parasitoids found.

Several resistant lines of wheat, Triticum aestivum (L.) (Poaceae), have been developed to control populations of the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Hemiptera: Aphididae). We examined the potential effects of D. noxia resistant lines on another aphid, the bird cherry-oat aphid (Rhopalosiphum padi (L.) (Hemiptera: Aphididae)), which commonly co-occurs with D. noxia. Because one type of resistance (mediated by the Dn1 gene) is purported to be induced rather than constitutive, we also determined the degree to which the suitability of resistant and susceptible plants is modified by previous infestation. Although resistant lines were derived from five different sources, we did not detect any differences in the population growth of R. padi on resistant and near-isogenic susceptible plants. The performance of D. noxia was reduced as expected on resistant plants but was unaffected by whether or not plants had been previously infested. In contrast, the performance of R. padi was reduced on plants that had been previously infested but was unaffected by whether plants were resistant or susceptible to D. noxia. Because neither species' performance was especially low on previously infested, resistant plants, there was no evidence that prior aphid feeding induces a higher level of resistance.

Ammonia has long been known to be an attractant for the apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) (Hodson 1943, 1948). The responses of apple maggot to ammonia release rates, however, have not been adequately determined. Ammonia release rates determined from mass losses of ammonium carbonate, ammonium acetate, and casein hydrolysate lures (e.g., Jones 1988; Reynolds and Prokopy 1997) do not take into account decomposition and release of compounds such as carbon dioxide or volatiles that may be moderately repellent (Bateman and Morton 1981; Mazor et al. 1987) or attractive to some Tephritidae flies (Mazor et al. 1987). In this study, the objectives were to determine the responses of apple maggot females and males in western Washington to ammonium hydroxide lures designed to release a wide range of ammonia. An emphasis was placed on identifying the ammonia release rates that elicit maximum fly responses.