Continuous-flow laboratory bioassays were used to assess the acute toxicities of four formulated insecticides to representative stream invertebrates. Toxicities (48-h LC50) ranged from 3.2 to 7.4 μg/L for permethrin, from 39 to 269 μg/L for fenitrothion, from 478 to 2863 μg/L for aminocarb, and from 99 to 492 μg/L for mexacarbate. Slopes of the probit lines were similar for acetylcholinesterase inhibitors (fenitrothion, aminocarb, and mexacarbate), but slightly lower for permethrin. All test species responded to all of the insecticides at concentrations of 0.25 μg/L for permethrin, 10 μg/L for fenithrothion, and 25 μg/L for aminocarb and mexacarbate by drifting in the test chambers.

The role of starvation, the occurrence of mating, and delays and the onset of mating on the retention of eggs by the gypsy moth, Lymantria dispar (L.), were evaluated. The mating status of female gypsy moths did influence egg retention.

Mating delays did not affect egg retention. Differences in the number of females retaining some eggs were found among females whose larvae had been reared on different host plants. The amount of food consumed had a significant effect on egg retention. Partial starvation had an impact on egg retention and on larval and pupal development, pupal size, and total egg production. The greater the starvation the greater the egg retention. The ecological implications of these results are discussed.

The larvae of jack pine budworm, Choristoneura pinus pinus Free., were reared individually on diet in the laboratory. Observation of ecdysis and measurement of the corresponding head capsules identified seven distinct instars. Parasitism by the common larval parasitoid Apanteles fumiferanae Vier. resulted in smaller head capsule size and retarded development during the fourth, fifth, and sixth instars of the jack pine bud worm.

Collection of Podocinum pacificum Berlese from southeastern Ontario represents the first record of the mite family Podocinidae in Canada. Other distribution records including the northerly extent of this species in North America are discussed.

Using regression analysis on data compiled from the literature, I compared relationships (forewing versus body length) of mayfly imagoes, as a measure of dispersal, between suborders (Schistonota and Pannota) and among habitat type (lotic, lentic, and mixed). There were no significant differences in slopes or intercepts of the regression lines between sexes. Forewing length changed less markedly with body size for species within the ancestral Schistonota than the Pannota. Regression lines for lake and river forms intersect at 7.85 mm (wing length) and 7.30 mm (body length). Small (body length < 7.3 mm) lentic mayflies have proportionately longer wings than small riverine forms. Large (body length > 7.3 mm) riverine mayflies have proportionately longer wings than lentic forms. Based on these relationships, small lake-dwelling mayflies and large riverine mayflies are best able to disperse. Mayfly species occurring in mixed (both rivers and lakes) habitats exhibited allometric relationships similar to mayflies restricted to rivers.

Inheritance of gregarious or solitary oviposition in Muscidifurax raptorellus Kogan and Legner involves two phases: (1) the female parasitoid expresses either trait shortly after mating, the magnitude of which is apparently determined by the male genome; and (2) the trait is then apparently fixed into a genome of her offspring who demonstrate it in the virgin state. In the first phase, less than one-half the magnitude of behavioral expression is shown, full expression occurring in the F1 diploid virgin hybrid. In matings with hybrids produced from subsequent backcrosses, more than one-half of the behavior is expressed shortly after mating. Traits related to gregarious oviposition (number parasitoids developed per host and total progeny) were also similarly initially expressed and subsequently inherited. A polygenic mode of inheritance is apparent, with ≥3-22 genes estimated. The extranuclear influences prior to inheritance may involve microorganisms and/or chemicals (enzymes) present in hymenopteran seminal fluid. Natural selection in this system should be accelerated by males causing the expression of a portion of the quantity of heritable behavior within the same generation.

In the course of benthic sampling during 1981 and 1982 in Lake St. Louis, Que., 28 water mite larvae (Hygrobatidae: Hygrobates) were found parasitizing caddisfly larvae (Leptoceridae: Nectopsyche, Oecetis, Ceraclea). Two other water mite larvae (Unionicolidae: Unionicola) also were found: one on Nectopsyche from Lake St. Louis, and the other on Limnephilus (Limnephilidae) from the Magundy Stream, N.B. Prevalence of parasitism ranged from 8 to 42%. Mite distribution among available hosts suggests host selection by the mites or the absence of mites from certain microhabitats. Parasitism of fully submerged insect larvae by mite larvae represents a further derivation from ancestral behavior patterns. This paper describes five of the seven documented cases of such parasitism on Trichoptera larvae.

The reliability of three methods for sampling aphidophagous coccinellids and syrphids in a winter wheat field was compared.

In the first method, an observer recorded predators seen during 2 min per 25-m2 sub-plot. In the second, two observers worked successively through each plot, scanning the full height of wheat plants and collecting predators. This method enables calculation of predator density using De Lury’s technique. The third method consisted of collecting wheat plants from each sub-plot for examination in the laboratory.

The first method may be used for appraising populations of adult coccinellids on a large scale. The detailed searching method is appropriate for studies of the population dynamics of adult and fourth-instar coccinellids. The plant sampling method is the most accurate for assesssing densities of syrphid larvae and pupae.

Stethynium Enock, a mainly old world genus most of whose members occur in Australia, is redescribed based on study of the non-Australian species. The subgenus Neostethynium Ogloblin is removed from Stethynium and given generic status. The names S. faunum Girault and S. empoascae Subba Rao are synonymized under S. triclavatum Enock. A lectotype is designated for S. triclavatum. Stethynium angustipennesp. n. is described.

Schizophragma Ogloblin, formerly a subgenus of Patasson, is redescribed as a genus. Anaphes bicolor Dozier and Stethynium annulatum Doutt are transferred to Schizophragma. The names S. annulatum and S. nana Ogloblin are synonymized, respectively, under S. bicolor and S. parvula Ogloblin. Lectotypes are designated for S. bicolor (Dozier) and S. latipennis (Crawford). A provisional key to the species of Schizophragma is presented.

In 1984 and 1985 a total of 51 mummies of the genus Therioaphis sp. (Hornoptera: Aphididae) were collected on alfalfa, Medicago sativa L., in several localities in southern Manitoba: Glenlea, Oakbank, Rosenort, St. Adolphe, and Ste. Agathe [status of North American species of Therioaphis is uncertain; some workers regard Therioaphis on alfalfa and those on clover as different species, whereas others regard those found on alfalfa as merely strains of the species from clover (A.G. Robinson, personal comrnunication)]. The mummies were held in gelatin capsules at 20°C and a 16L:8D cycle, and 44 parasite adults that emerged were identified. Two primary parasites pecies. Praon exsolelurn (Nees) and Binodoxys sp. (Hymenoptera: Aphidiidae), were recorded (Table 1). Cocoons from which adults of P. exsoleturn emerged were formed between the mummy and the substratum, whereas cocoons of the two Binodoxys specimens were inside the mummies. The three secondary parasite species (Table 1) emerged only from the hosts with external cocoons and presumably had developed on P. exsoleturn. Each of the seven hosts from which no parasites emerged had an external cocoon which contained a decomposed parasite larva, either P. exsoletum or one of the secondary species.