A synthesis of observations on density-dependent interactions in parasitoid populations is attempted, working from the particular aspects of discrimination against parasitized hosts and detailed observations on parasitoid behavior, to more general aspects of parasitoid ecology, dispersal, distribution, and response to host populations. Females of Pleolophus basizonus (Gravenhorst) are able to discriminate against parasitized hosts of Neodiprion swainei Middleton between narrow limits (mean densities of 0.4 to 1.4 eggs per cocoon) set by the probability of a female finding an unparasitized host. They show mutual interference in egg laying at high parasitoid:host ratios, and a density-dependent escape reaction to adult parasitoid density. These behaviors all result from the recognition of repellent trail odors left by searching females. Response of individual females to high parasitoid densities may therefore lead to dispersal, the occupation by the population of more, but not so favorable habitats, and an apparent density-independent response to host populations.

The preferred host of the cluster fly, Pollenia rudis Fab., in Ontario is reported to be the earthworm Eisenia rosea Sav. Periodic field digging revealed the immature stages of P. rudis feeding, or in close association with, E. rosea. In addition P. rudis was reared in the laboratory on E. rosea but could not be reared on any of the other species of earthworm found in the field.For the first time in North America the complete life history, along with each of the immature stages of P. rudis, is described. The differences between P. rudis from North America and those from France are indicated.Finally, the authors speculate that there are two strains, or species, of P. rudis in France: one is host-specific to the earthworm Allolobophora chlorotica Sav. and the other to E. rosea. Only the strain with E. rosea as its preferred host has as yet been reported from Canada.

Observations were made during 1967 to 1969 at Ithaca, N.Y., supplemented by collections at New Cumberland and Carlisle, Pa., on arthropods associated with fungi occurring on alfalfa, Medicago saliva L. Five species of Coleoptera, two species of Diptera, one species each of Collembola and Psocoptera, and nine species of Acari were reared or collected consistently from fungus-covered alfalfa leaves, stems, and seed pods. Attraction to fungi on the plants, principally Alternaria sp., accounted for the presence on alfalfa of arthropod species that normally might be considered as accidentals or visitors. The mycetophagous species thus contributed to the richness of the alfalfa fauna. Immature stages of several species were collected only in late fall or on 3- or 4-year-old plants. The possible role of the fungus-feeding species in seasonal changes in the alfalfa fauna and changes in the fauna in successive years is discussed.

An eriophyoid mite, Nalepella halourga Keifer, is newly recorded in Canada from two hosts: black spruce, Picea mariana (Mill.) BSP., from Ontario, and Norway spruce, Picea abies (L.) Karst., from New Brunswick. For the first time this mite is reported as damaging black spruce under greenhouse conditions. A key to the eight described species of Nalepella and notes on their host associations and economic importance are included.

Diapause in Wyeomyia smithii (Coquillett) was shown to be a function of photoperiod, and independent of temperature. The critical daylength for a population from Pinawa, Man., was 15 hr light per diem. The photoperiodic cues are monitored by the early instars, with diapause being expressed in the third instar. Development is also limited by temperatures below 15 °C even when the critical daylength is exceeded.

Survival at low and subzero temperatures is aided by the diapause state. However, larvae are unable to withstand extended periods of subzero temperatures, even in the diapause condition. At −5 °C, 60% mortality occurred after 8 weeks under laboratory conditions. In the field, where ground temperatures averaged −3.7 °C during the five coldest months, larval mortality averaged 45% after four winter months.

Once diapause is established, larvae consume very little food. Diapause larvae appear to be as active as non-diapause larvae, and also appear to be feeding constantly. However, the amount of food ingested is negligible compared to non-diapause larvae.

A European bug Picromerus bidens (L.) is reported from Quebec feeding on larvae of the introduced sawfly Gilpinia frutetorum (F.) (Hymenoptera: Diprionidae). A colour photograph of the bug and an illustration of the anterior femur and tibia are included.

Allometric growth of antennal and leg segments was studied in five species of mirids, namely, Adelphocoris lineolalus (Goeze), A. rapidus (Say), Lygus lineolaris (Beauv.), Polymerus basalts Reuter, and Plagiognathus chrysanthemi (Wolff). The study revealed that growth ratios of both A. lineolatus and A. rapidus varied in parallel fashion in homologous segments of L. lineolaris and, that those of P. chrysanthemi varied similarly with L. lineolaris and P. basalis. It was also found that segments with relatively high growth ratios were less different in magnitude than slowly growing segments when both A. lineolatus and A. rapidus were compared with L. lineolaris and P. basalis. Growth ratios of head width were similar for the five species. The probable evolution of relative growth was discussed.

The western spruce budworm, Choiistoneura occidentalis Freeman, which normally passes through an obligate diapause in nature, was reared in the laboratory without diapause. The critical factor for preventing diapause appeared to be the physical environment presented to the first stage larvae. The response of C. occidentalis was flexible. The 2nd stage larvae could be made to diapause or forego diapause, depending on their rearing experience in the first stage. By eliminating diapause it was possible to rear about 7½ generations per year as against about 2¼ under normal diapause conditions. The diapause of the jack-pine budworm, C. pinus pinus Freeman, and C. lambertiana californica Powell, could be prevented by the same technique. The diapause of the spruce budworm, C. fumiferana (Clemens), could not be eliminated except after several generations of selection.

Studies on the courtship behavior of Melanoplus sanguinipes (Fabr.) clearly indicated that the male played the dominant role. The conspicuous waving of antennae and vibrating of hind femora, which form an integral part of the male’s behavioral pattern, did not appear essential for normal coupling. Visual stimuli proved to be of primary importance for ’homing in’ on the female prior to the mounting leap. Blinding the male caused all courtship activities to cease. Males clearly were able to select mature females from immature ones and virgin from mated females. Although further experimental evidence is required for corroboration, it is suggested that this selectivity may have been accomplished by some form of chemical stimulus emitted by the females.

Four new species of Dichrooscytus Fieber are described: flagellatus and rufusculus from British Columbia, and rostratus and rubidus from Alberta and British Columbia. New records for Canada are: convexifrons Knight, flavescens Knight, irroratus Van Duzee, latifrons Knight, rainieri Knight, ruberellus Knight, and rufipennis Fallen. Key to species, additional records on distribution and host plants, and illustrations of the male genitalia of all the species occurring in Canada are presented.

Releases of chemosterilized stable flies, Stomoxys calcitrans (L.), that equalled existing field populations (1:1 ratio) markedly reduced a field population in Florida. The released insects were relatively long lived in the field and did not migrate far from the nearest source of food and oviposition medium.

The leafhopper Erythroneura ziczac Walsh is the most important insect on grape in the Okanagan Valley, B.C. Hairy-leaved varieties of grape are relatively resistant to attack. The leafhopper has two overlapping generations a year and overwinters in the adult stage. Its chief natural enemy is a mymarid egg-parasite, Anagrus epos Girault, which overwinters in the eggs of other species of leaf-hoppers on wild rose and apple so that intensity of parasitism of E. ziczac can be influenced by proximity of those plants to vineyards.

Tenebrio molitor L. eggs in 15 age groups ranging from 0.5 to 7.5 days were irradiated with 10 dosages of gamma radiation ranging from 0.5 to 160 krad. The study showed that age had a pronounced effect on radiation-induced egg mortality. There was a 250-fold increase in resistance as eggs matured from 0.5 to 7.5 days as measured by the dosage required to produce an LD50.

Residues of methomyl in rape plants and seed were determined after its application for bertha armyworm control. In one experiment application of 3 oz of methomyl per acre left 17 p.p.m. residue on the rape plants immediately after application. This level rapidly declined to 1.5, 1.0, 0.4, and 0.2 p.p.m. 1, 2, 5, and 9 days later, respectively, and no residue was detected (less than 0.02 p.p.m.) in seed harvested 22 days after application of the toxicant. Rape plant samples collected from several farms immediately after the application of 3 to 4 oz of methomyl per acre had 2.5 to 16 p.p.m. residues, indicating inefficient application of the insecticide in some cases. Analysis of rape seed samples collected from 36 farms showed little residue in three samples (0.02 to 0.03 p.p.m.) and none in 33, indicating that the use of methomyl for bertha armyworm control is not likely to contaminate rape seed with undesirable levels of residues.

The sex ratios at emergence of some Chironomidae from ponds in the Hazen Camp area (81°49′ N., 71°18′ W.) are given from trap records for a number of seasons.

In Tanypodinae and Chironomini there are apparently about equal numbers of the sexes; in Tanytarsini and most Orthocladiinae females consistently outnumber males, often forming 60% or more of the total emergence. These findings are discussed: the presence of facultative parthenogenesis in some species is thought to be likely.

A detailed analysis of male courtship behavior in Phodaga alticeps LeC. is presented. Although behavior in this species shares the basic pattern characterizing the subfamily Meloinae, several unique features are present. These include the mounted male being supported primarily by the substrate rather than the body of the female, and the anterior positioning of the male’s middle legs during most of the courtship period. Male stimulation of the female is tactual in nature and consists of periodically curling the antennae around those of the female and at the same time stimulating her maxillary palpi with the middle legs. Bouts of tactual display alternate throughout courtship with periods of male quiescence. Genital insertion attempts are rare in this species and probably occur only prior to copulation. Besides a description of male behavior the structural modifications functionally correlated with courtship are described; and concomitant female behavior and its effects on the male are discussed. In addition, the pattern of courtship in P. alticeps is compared to that of other meloids. Particular attention is given to behavior in its closest relative, Negalius marmoratus Casey.Other aspects of the bionomics of P. alticeps are also treated in this paper. Geographic distribution, seasonal distribution, feeding behavior, defense, antennal cleaning, and oviposition behavior are stressed.

Salticid spiders of the genus Continusa were present in 61% of the nests of dolichoderine ants (Tapinoma melanocephalum (Fabricius)) which build their nests on the undersides of leaves in the lower forest canopy on the Osa peninsula of Costa Rica. Cutting and displacement of the supporting leaves caused abandonment of 80% of the nests within 4 days and experiments carried out by marking and displacing the spider indicated their tenacity to the ant nest. T. melanocephalum nests which contained spiders were more successful in terms of the brood to adult ratio.

The effect of temperature on prepupal diapause development in the hymenopteran Megachile rotundata (F.) was investigated by storing prepupae at various temperatures from −20° to 28 °C prior to final incubation at 28 °C. Preincubation temperatures of 5°, 10°, and 15 °C proved equally effective for diapause development and for the synchronization of adult emergence. Lower temperatures resulted in less synchronous emergence and higher mortality. When prepupae were exposed to more moderate temperature regimes prior to storage at lower temperatures, adult emergence became more synchronized and mortality declined. A high percentage of bees emerged after storage at 20 °C but their emergence was poorly synchronized. Over 50% of the prepupae stored at 28 °C developed without prior treatment at lower temperature but emergence was even less synchronized. The results of these experiments show that all prepupae diapause but the rate of diapause development becomes increasingly variable above and below an optimal range of 5° to 15 °C.

The lipids of loblolly pine phloem, particularly the neutral lipids, were fractionated and bioassayed for feeding stimulant activity with the pales weevil, Hylobius pales (Herbst). Activity was evidently reduced by the fractionation procedures. Significant feeding occurred in response to the fraction whose principal constituent was β-sitosterol. Also, evidence indicated that substances occurring with the sterols may play a part in inducing feeding.