In the field, superparasitism of Lymantria dispar (L.) by Parasetigena silvestris (Robineau-Desvoidy) was not the result of random oviposition, but, because parasitoid eggs were aggregated, certain hosts were more likely to be parasitized than average. Parasitoid eggs were more aggregated when gypsy moth larvae were collected from under burlap bands than when larvae were collected elsewhere in the same 9-ha plot, resulting in lowered mortality due to parasitism. This finding suggests that collecting larvae from burlap bands may not provide accurate estimates of the impact of P. silvestris on populations of L. dispar. In laboratory studies, deposition of more than one egg on a single host significantly increased parasitoid emergence and host mortality. However, increasing superparasitism had a negative effect on both the probability that an individual parasitoid would survive to emerge from a host and the size of the puparium produced by the parasitoid. The probability of parasitoid survival was higher when fifth- rather than fourth-instar gypsy moth larvae were attacked, but puparia produced by parasitoids emerging from fifth-instar larvae were smaller.

A study was conducted to evaluate changes in rangeland grasshopper communities over a 5-year period in the Agropyron spicatum (Pursh) Scribn. and Smith and Bouteloua gracilis (H.B.K.) Lag. provinces of the steppe region of Montana, USA. Results showed that it was possible to categorize years into outbreak, non-outbreak, and transitional based on rangeland grasshopper intensity. Nearly twice as many species were observed in outbreak versus non-outbreak years. Of the 57 total grasshopper species collected over the entire study period, 16 species were found only during outbreak years and only two were found exclusively during non-outbreak years. Of the remaining 39 species collected during outbreak and non-outbreak years, 27 species showed no significant differences in the percentage of the community that they represented and 11 species showed significant increases. The only species that made up proportionately less of the community as densities declined from outbreak to non-outbreak was Melanoplus sanguinipes (F.). Although M. sanguinipes, Ageneotettix deorum (Scudder), and Aulocara elliotti (Thomas) were the three top-ranked species in both outbreak and non-outbreak years, M. sanguinipes contributed most to overall shifts in grasshopper intensity. Results support the hypothesis that grasshopper communities overall are sensitive to temporal changes in resources, even though responses of individual species differed.

Morphological, life history, and distributional data are presented for North American species of the genus Chelomideopsis Romijn. Chelomideopsis brunsoni (Cook) and C. besselingi (Cook) are redescribed on the basis of larvae, deutonymphs, and adults. Larvae and female adults of C. brunsoni, and deutonymphs of both of these species, are described for the first time. The mite described by Cook (1955) as the allotype female of C. brunsoni is correctly identified as a female of Platyhydracarus juliani Smith (1989). Four new species are described as follows: C. occidentalis sp.nov. (deutonymphs and adults), C. siskiyouensis sp.nov. (adults), C. minuta sp.nov. (female adults), and C. gledhilli sp.nov. (adults). A new diagnosis is proposed for Chelomideopsis based on knowledge of all active instars. New hypotheses on the phylogeny of species of the genus are presented, permitting the first assessment of zoogeography in this group of mites. The genus probably originated in Laurasia during the late Cretaceous or early Tertiary, and diversified and became widely dispersed in North America and Eurasia during the Tertiary. Mites of the genus apparently were adapted for the temperate climate that persisted until late Tertiary times, and were displaced to southern refugial areas by habitat destruction and climatic cooling associated with episodes of Pleistocene glaciation. The various species are now beginning to reinvade recently deglaciated areas from their Wisconsinan refugia, as they and their host chironomids colonize suitable spring and small stream habitats.

The adult, pupa, and final-instar larva of Trichothaumalea elakalensis sp.nov. (Diptera: Thaumaleidae) are described and illustrated. This is the first record of this genus from eastern North America and first description of the immature stages. In addition, reinterpretation of the homologies of the male terminalia and preliminary observations on the male reproductive system of Thaumaleidae are presented and the phylogenetic implications upon the monophyly of the Chironomoidea are discussed.

In laboratory and field observations, male and female orange wheat blossom midge, Sitodiplosis mosellana (Géhin), emerged in late afternoon and early evening, with males emerging 1–2 h before females on average within a given day. Under laboratory conditions, males also emerged on average 0–3 days before females in three different experiments. Within 1 h of emergence, virgin females began to extend their ovipositors much of the time. This behaviour ceased upon mating, and was presumed to be calling behaviour: behaviour associated with pheromone release. Calling behaviour exhibited a daily rhythm both under controlled and field conditions. Females gradually increased the time spent calling in the last few hours of the photophase and called more than two-thirds of the time during the scotophase. Mating was preceded by wing vibration in the male prior to and during a walking approach. Receptive females spread their wings which facilitated mating. Mean duration of mating was 171 ± 15 s (±SE).

The effects of Tomicobia tibialis Ashmead on the reproductive potential of adult Ips pini (Say) females were examined by comparing reproductive indices of parasitized and healthy females maintained in groups of three with healthy males. Parasitized females produced 50% fewer offspring than healthy females, and these offspring were distributed differently in the maternal gallery. Maternal gallery length and larval survival were not significantly different between the two groups, but a statistical power analysis (1 − β) shows this result to be equivocal. The potential to use T. tibialis as a biocontrol agent against I. pini is discussed.

Weight gain during the penultimate and ultimate stadia of the pale western cutworm, Agrotis orthogonia Morr., comprises about 37% and 39%, respectively, of the maximum larval weight. For the army cutworm, Euxoa auxiliaris (Grt.), the corresponding values are 20% and 69%. The proportion of final larval weight that is gained by the ultimate-instar larva of the army cutworm is similar to that reported for other noctuids, whereas the proportion gained by the ultimate-instar larva of the pale western cutworm is much lower and is likely related to the prepupal aestivation that occurs in this species. Because of the growth pattern of pale western cutworm, a substantial proportion of total food consumption, and consequently, crop damage, occurs during the penultimate stadium of this species.

Carabid beetles were collected with grids of pitfall traps during two seasons in five habitats in the ecotone between aspen parkland and boreal mixedwood forest in central Alberta. The 23 abundant species (54 species in total) were divided into the following four distributional types: (1) Pterostichus adstrictus Eschz. was numerous in all five habitats (habitat generalist); (2) Platynus decentis Say, Calathus ingratus Dej., and Scaphinotus marginatus Fisch. were abundant in all four forest habitats (forest generalists); (3) another 10 species were common in one or two forest habitats (forest specialists); (4) nine species, representing mainly Agonum, Amara, and Bembidion, were restricted to a recently cleared timothy–clover grassland (meadow species). Soil moisture seemed to be important in determining habitat associations of the species among the forest types. Captures of most species were aggregated also within habitats, and the consistency of aggregation among particular traps suggests that it is mainly a response to subtle microhabitat differences. All abundant species, except S. marginatus, showed a peak of capture in May–June. Number of species, corrected for sample size by rarefaction, was highest in the meadow (27.5) and lowest in the dry upland aspen forest (11.9). Species diversity was highest in meadow and the lakeside forest habitats, but carabid assemblages of the four forest habitats were more similar to each other than to the meadow assemblage.

The phenology and reproductive status of adults of the redbacked cutworm, Euxoa ochrogaster (Guenée), were determined from blacklight (BLT) and sex-attractant (SAT) trap catches at four locations in southern Manitoba in 1987 through 1989. The flight period was of 9–12 weeks duration, extending from late June to early October. The first male and female moths were captured at about the same time in the BLT and SAT. The peak catches of the BLT occurred during the first 3 weeks of August (weeks 5 and 6 of the flight period) and those of the SAT about 1 week later. The SAT continued to capture male moths for 2–3 weeks after the last moths appeared in the BLT. Most females captured during the first 2–3 weeks of the flight period were virgins who had not yet initiated egg development. Most mating, egg development, and oviposition took place during a 3- to 4-week period that included the 2 weeks before, the same week as, and the week after the peak BLT catches (weeks 3–7 of the flight period); these activities occurred in the 3–4 weeks before the peak SAT catches. The data suggested that there was competition between SAT and females in attracting males and, consequently, the SAT catch data may not be providing accurate measurements of the sizes of breeding populations of males in the field. The BLT catches underestimated the length of the flight period by about 1.5–3 weeks.

Blacklight traps (BLT) are commonly used in trapping and monitoring systems (Harding et al. 1966), employing either a 12-V battery or commercial alternating current as the power source. Both power systems have major disadvantages. Batteries need to be recharged frequently (every 2–3 days), and the commercial alternating current system often restricts the BLT to locations that are not well suited for trapping or monitoring. We describe here a portable, solar-powered charging system for 12-V batteries, which we developed to overcome the disadvantages of these power systems.

Morphological and physical characteristics of plants, such as trichomes (pubescence), surface waxes, silication, toughness, sclerotization, colour, and shape may affect herbivory by providing inhospitable surfaces or by eliciting altered host behaviour (review by Noms and Kogan 1980). Even slight variations in the morphological structure of plants may enhance their fitness and form the basis of resistance. Seedlings of the hybrid cabbage, Brassica oleraceae L. cv. Survivor, provide an intriguing opportunity to study within the same plant the influence of radically different cotyledon morphology on the feeding behaviour of the crucifer flea beetle, Phyllotreta cruciferae Goeze, because a high proportion of seedlings of this cultivar (>92%) have one folded cotyledon. The condition arises from a failure of the inner cotyledon of the embryo to open fully and assume a normal horizontal plane after germination. The outer cotyledon is invariably normal and both cotyledons appear to grow at about the same rate (unpublished data). The degree of folding varies from cotyledons that are only a few degrees from horizontal to those that are fully folded and 90° from horizontal. This study reports the distribution and feeding of P. cruciferae on the morphologically different cotyledons of B. oleraceae cv. Survivor.

The alfalfa leafcutting bee, Megachile rotundata (Fab.), is a domesticated pollinator important for alfalfa seed production in western Canada. Populations of M. rotundata are highly susceptible to chalkbrood, a disease caused by the fungus Ascosphaera aggregata Skou. The disease has caused high mortalities in M. rotundata populations in the northwestern United States since 1972. It was found in Manitoba in 1982, Alberta in 1983, and Saskatchewan in 1984 (Richards 1985). In subsequent surveys, A. aggregata has been detected only sporadically and at low levels of infection in Saskatchewan M. rotundata populations (Goerzen 1991). A previously reported observation of A. aggregata in the native leafcutting bee M. relativa Cresson (Goerzen et al. 1990) indicated that the disease is present in native leafcutting bee species which commonly immigrate into alfalfa leafcutting bee nest material.

Semiochemical-mediated behavior of the striped ambrosia beetle, Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae), has received extensive study. In selecting and mass-attacking hosts in nature, it utilizes a blend of volatiles, including the aggregation pheromone, lineatin, and the host kairomones α-pinene and ethanol (MacConnell et al. 1977; Vité and Bakke 1979; Borden et al. 1982; Bakke 1983; Lindgren et al. 1983). In single cell recordings of European T. lineatum olfactory cells, Tømmerås and Mustaparta (1989) reported no response to pheromones of other scolytid species. However, Benz et al. (1986) reported some response in the field by European T. lineatum to a blend of synthetic Ips typographus (L.) pheromones, although a single attractant was not identified. We report that frontalin, a pheromone utilized by numerous Dendroctonus spp., is an attractive kairomone for T. lineatum in western North America.

One of the more frequently used methods of sampling flying insects is the sticky trap. These traps are often used to evaluate the type and size of prey available for aerial insectivores, such as bats and birds (e.g. Barclay 1991; Brigham 1992). Non-attractant sticky traps are favoured because they are considered relatively bias-free, yielding a more representative sample than attractant traps (Service 1976). Sticky traps are versatile in that they are simple to construct and operate, portable, and relatively inexpensive. When using these traps, it is possible to sample insects economically in similar or different habitats and at various heights within habitats (Kunz 1988).

The use of pyrethroids in southern pine seed orchards to control seed and cone insects has sometimes resulted in outbreaks of scale insects (Nord et al. 1985). Onset of these infestations has been related in part to the relatively low contact toxicities of pyrethroids (Clarke et al. 1988). Pyrethroids have lower contact toxicities than organophosphorous insecticides against crawlers of the striped pine scale, Tourneyella pini (King). Our objective was to determine if a similar relationship existed for the pine tortoise scale, Tourneyella parvicornis (Cockerell), another scale insect pest that infests southern pine seed orchards.