Insects are selected for slow development (but relatively fast growth) in spring, but for fast development in summer. These contrasting selection pressures explain five puzzling effects of temperature on insects: growth and development rates increase almost linearly with temperature; genetic variability in development rate is reduced at high (27°C) temperatures; genetic variability in growth rate is reduced at low (15°C) temperatures; development is very slow at the time of emergence after diapause, regardless of the temperature threshold for emergence; and growth is slow at low temperatures, but development is even slower.

Insects use temperature to indicate time-of-season. Different species are geared differently to rising temperatures. Insect predators and parasitoids become more effective at high temperatures; and insect population dynamics are not stable in the conventional sense.

Triarthria Stephens is known from two species in the New World. One is T. setipennis (Fallen), introduced into North America from Europe early this century as a biological control agent against its host, the European earwig (Forficula auricularia L.) (Dermaptera: Forficulidae). The second species is T. parva (Townsend), a widely distributed earwig (Doru spp.) parasitoid in the Neotropical region. Triarthria parva was originally described in the monotypic genus Parkerella Townsend; Parkerella is newly synonymized with Triarthria (syn.nov.), and T. parva is a new combination (comb.nov.). The genus Triarthria is diagnosed and the four included species are keyed: T. legeri (Villeneuve) (western Palearctic region), T. tienshanensis Ziegler (Uzbekistan), T. setipennis, and T. parva. The two species in the New World are diagnosed, illustrated, and their known distributions mapped.

We determined variations in selected life-history parameters in a tritrophic system that consisted of a plant (broad bean, Vicia faba L.), an aphid (pea aphid, Acyrthosiphon pisum), and an aphid parasitoid (Ephedras californicus). We manipulated plant and aphid quality by growing bean plants in a high- and a low-quality nutrient solution for three generations. Pea aphids adapted to reduced nutrient availability by differentially allocating resources to somatic and gonadal growth across generations. On low-quality plants, time from birth to adult increased and dry mass decreased. The number of sclerotized embryos was correlated with adult dry mass. By contrast, in E. californicus, variations in dry mass, rate of development, and number of ovarial eggs did not suggest transgenerational adaptations to resource quality as measured by aphid size. The number of mature eggs was dependent on female age. Development time varied with parasitoid sex and was independent of aphid stage at the time of death. In the low-quality treatment, males survived on average longer than females eclosing from the same kinds of hosts.

Aphids and their parasitoids have evolved flexible life-history strategies in response to variations in plant quality. Pea aphids adapted to qualitatively variable resources by optimizing the balance between somatic and gonadal investment across successive generations. But E. californicus responded to low host quality at the level of the individual, rather than across generations; the trade-off pattern was influenced by the host’s growth potential after parasitization.

The diapause response to photoperiod in Ontario populations of Cotesia melanoscela, an introduced parasitoid of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), was investigated under a series of stationary photoperiods and constant temperature. When the parasitic larval stages of C. melanoscela were exposed to different photoperiods, the insect exhibited a typical long-day response: long days (greater than 18 h) promoted continuous development whereas short days (less than 16 h) resulted in diapause in the cocooned prepupal stage. Within the region of the critical photoperiod (16–18 h) the diapause response was associated with larval development time. Individuals that developed more slowly were more likely to enter diapause. Cotesia melanoscela was sensitive to photoperiod throughout its entire larval period. These individual responses are used to interpret patterns of seasonality of the parasitoid in Ontario and to compare with published information from populations of C. melanoscela in New England.

Four indicators of productivity and quality for the alfalfa leafcutter bee, Megachile rotundata (Fab.), were examined over a 3-year period and the influence of different shelter designs, nesting materials, and 34 environmental variables evaluated. A higher percentage of cocoons per total cells was produced in polystyrene nesting material than in pinewood nesting material. Both nesting materials had similar percentages of tunnels capped or containing cells and total numbers of cells per hive. Shelters with conspicuous orientation patterns or silhouettes had more tunnels capped per hive, tunnels with cells, and greater total cell production per hive than did other shelter designs. The time of maximum bee production varied greatly among the 3 years. Many environmental variables, especially those associated with higher temperature, heat units, and mean actual temperature, had a significant positive effect on bee productivity and cell quality. The information contained in this study may help delineate those climatic areas where this valuable alfalfa pollinator can be most effective, and may assist beekeepers in making management decisions that will improve their operations.

Male spruce budworm moths were kept in a wind tunnel for 4 days and assayed each day to determine their ability to locate calling females that were surrounded by rubber septa loaded with synthetic pheromone, a 95:5 blend of E:Z-11-tetradecenal. As the concentration of synthetic pheromone increased, the numbers of males successfully locating females decreased, the latency of response increased, and the speed of flight decreased. At release rates from the septa close to those of a calling female, 6–60 ng/h per septum, most disrupted males flew to a septum instead of the females. At the highest release rate tested, 600 ng/h, many males were inactive or flew to the sides of the tunnel, which indicates sensory fatigue. This effect was more pronounced among males that were continuously exposed to the synthetic pheromone for the 4 days than among males kept in pheromone-free air between assays. About a quarter of the males died or became unable to fly after the 4 days, but there was no change in the proportions of the different responses of males, or in their response times, with increasing age, nor was there evidence that males were conditioned by their experience on previous days. The results led to the conclusion that time-averaged atmospheric concentrations of the synthetic pheromone as high as 20 ng/m3 are necessary to achieve effective disruption of the orientation of male spruce budworm moths to calling female moths.

A 2-year field study was carried out to locate and identify eggs, determine the temporal distributions of eggs and larvae, and assess the impact of Strobilomyia laricis and S. viaria on Larix laricina. Eggs of S. laricis were beige with a patterned surface and usually laid one per cone in the bud scales at the base of the cone. Eggs of S. viaria were white and smooth and usually laid one per cone between the ovuliferous scales of the cone. Strobilomyia laricis oviposited from mid- to late May and S. viaria from late May to mid-June, each species initiating oviposition at a different stage of cone phenology. Peak egg densities of S. laricis were 25 and 65% higher than those of S. viaria in 1990 and 1991, respectively. Larvae of both species completed development at the same time, from mid-June to early July. The mean number of scales eaten per cone did not differ between species; one larva damaged a mean of 8.4 scales per cone in 1990 and 10.7 scales per cone in 1991. As the number of scales per cone increased, the mean number of scales eaten increased and the mean percentage of scales eaten decreased. Cone crops were light in both years. In 1990, the only year we were able to differentiate cone maggot larvae, 44% of cones were damaged by S. laricis and only 16% by S. viaria. Together, S. laricis and S. viaria damaged 60 and 67% of the cones and destroyed 38 and 50% of the potential seed crop in 1990 and 1991, respectively.

Timema douglasi sp.nov. is described from southwestern Oregon and northern California, USA. It is the third parthenogenetic species in the genus and is a specialist feeder on old-growth Douglas fir, occasionally causing serious defoliation. Timema knulli Strohecker is synonymized with Timema californicum Scudder.

The state of taxonomy of Idris, egg parasitoids of spiders, in Nearctic North America is reviewed. The concept of Idris is discussed and Ceralobaeus Ashmead is considered a junior synonym (new synonymy). The melleus-group of Idris is defined and 11 Nearctic species are keyed and described: I. castaneus sp.nov. (south and southeastern USA), I. chrysion sp.nov. (southeastern USA), I. costatus sp.nov. (eastern USA), I. lacunatus (Baja California, Mexico). I. leedsi sp.nov. (midsouthem USA), I. melleus (Ashrnead) (south and southeastern USA and southern Canada), I. onychion sp.nov. (southeastern USA), I. ornatus sp.nov. (eastern USA), I. pulvinus sp.nov. (south and southeastern USA), I. spartinae sp.nov. (southeastern USA), and I. triticola sp.nov. (midwestern USA). Extra-limital Nearctic members of the melleus-group are briefly discussed.

Louis Paul Mesnil (1904–1986) wrote more than 90 published articles on the Tachinidae between 1936 and 1980. He proposed, in those works, a total of 172 new genus-group names and 838 new species-group names. These genus-group and species-group names are listed here along with annotations and a complete record of Mesnil’s publications on the Tachinidae. Certain nomenclatural problems concerning the taxa of Mesnil are addressed, namely difficulties arising from the fascicle format of the series “Die Fliegen der palaearktischen Region”, determination of the type status of primary types (syntypes vs. holotypes), improperly labeled types in collections, taxa described in cryptic fashion, type depositories not slated or since changed, and manuscript names in collections. The rules of the International Code of Zoological Nomenclature are followed to standardize usage of Mesnil’s names.

Requirements for diapause development of larvae of Choristoneura fumiferana have been generally believed to be met by temperatures of 2°C or below for a period ranging from 14 to 20 weeks (see review by Sanders 1991), whereas those favourable for post-diapause development were shown to be above 11°C (Régnière 1990). However, we noticed that a large number of larvae completed diapause after 10 weeks at 18°C without any cold storage. The following experiment was carried out to confirm this result.