Statistical analysis of traffic data at the nest entrance of a colony of the yellowjacket, Vespula arenaria (F.), showed no evidence for the operation of social facilitation of the type described by Blackith (1957). As in bumble bees, the appearance of contagion in the temporal distribution of exits and sorties is the result of overall change in flight activity and is not due to social interaction between wasps.

The developmental sequence of the asexual generation of the gall wasp Acraspis hirta Bassett (Hymenoptera: Cynipidae) on its host plant Quercus prinus (Fagaceae) is described from a site in New Jersey. Chalcid attack was the key mortality factor in the gall population. Parasitoids concentrated their attack on host galls before galls matured and hardened. Hardening of gall walls appears to be the most important deterrent to later attack by inhibiting oviposition. Parasitoids which emerged from A. hirta galls did not reinfest the surviving hosts but probably shifted to other gall species. The parasitoids of Cynips divisa, a similar Old World gall species, became progressively more generalized in their feeding preferences as the season progressed. No such temporal sequencing wau observed in A. hirta.

Spacing out of A. hirta galls among leaves is an important strategy for increasing individual fitness in response to parasitoid attack. Most trees were sparsely infested, and few leaves supported more than one gall. Parasitoid mortality was significantly higher on multiply infected leaves than on leaves with one gall. Galls which were parasitized had a significantly smaller average distance to the nearest neighboring gall than those that escaped parasitism suggesting a slight resource concentration effect.

The Nearctic species, as well as several Palearctic species, of Athous Eschscholtz, Harminius Fairmaire, Hemicrepidius Germar, and Acanthathous Champion are studied and rearranged with the following new combinations: the Nearctic Hemicrepidius simplex (LeConte), H. falli (Reitter), and H. palpalis (Fall) (each from Athous); the Palearctic Hemicrepidius hirtus (Herbst) and H. niger (Linnaeus) (each from Athous); Hemicrepidius dauricus (Mannerheim) and H. flavipennis (Cherepanov) (each from Harminius); Hemicrepidius inornatus (Lewis) (from Yukara); and Acanthathous photinoides (Champion), A. campanulatus (Champion), A. mexicanus (Candèze), A. aequinoctialis (Champion), A. marcidus (Champion), A. aztecus (Champion), A. rugipennis (Champion), A. angusticollis (Champion), A. carinicollis (Champion), and A. championi (Schwarz) (each from Athous). Hemicrepidius hirtus (Candèze) (nee hirtus Herbst) is renamed californicus, new name, and the name H. hemipodus (Say) is recognized rather than decoloratus (Say). Pertinent generic characters are illustrated and brief notes are given for each of the above species (except those in Acanthathous) and for Harminius (Diacanthous) triundulatus (Mannerheim), H. (D.) undulatus (DeGeer), and Hemicrepidius pallidipennis (Mannerheim). Renter’s two subgenera of Harminius: Diacanthous and Megathous are recognized. A key to the genera associated with Athous and to the subgenera of Harminius is provided.

Pyrrhalta viburni (Paykull), a native of Eurasia, is reported for the first time as established in North America. In the Ottawa, Ont., area (including Hull, Que.) adults were very abundant and causing considerable damage to cultivated varieties of Viburnum opulus L. and moderate damage to the native V. Rafinesquianum Schultes. Photographs, a comparison with the similar species, P. luteola (Müller), and a brief note on egg laying are given.

An interesting, highly unusual chalcidoid wasp was found recently for Dr. L. Masner in material collected for him by Mr. F. M. Oliveira from Brazil. This unique specimen proved to belong to an undescribed genus in the subfamily Aximinae of the family Eurytomidae. It keys to the genera Axima Walker and Conoaxima Brues in Burks’ (1971) key to the genera of Eurytomidae, but differs in a number of morphological characters discussed below.

The structure and sculpture of this unique female specimen are illustrated by scanning electron photographs, the wings and antennae by macrophotography.

Adults of two new species of Trisetacus are described, T. strobi from foliage of Eastern White Pine and T. laricinae from buds of Tamarack.

Data are presented which show that first brood codling moth larvae have a higher diapause rate (and are thus univoltine) if reared in apples crowded with other larvae than if they are reared in uncrowded apples. From this relationship, a theoretical mechanism is proposed to help explain the interaction of genetic and nutritional effects in determining the dominant voltinism strain in codling moth populations.

Relationships of egg niches and eggs per unit (cm) of gallery were studied. On average egg niches were found to overestimate eggs by 36%. The rate of egg deposition in the mid-portion of the infested bole was found to be less than the upper and lower portion.

During a 2-year period, 47 species of spiders in 37 genera were taken in pitfall traps set within, or bordering a wheat field near Clavet, Saskatchewan. Species diversity and evenness were determined for the collections from both areas. Lycosids were predominant, both in the field and in the field borders. Seasonal distribution of captures of the two most common species, Arctosa emertoni Gertsch and Pardosa nebraska Chamberlin & Ivie, are given.

An annotated list is given of 48 species of aphids collected 1974–1977 at Churchill, Manitoba. Four new species are described: Acyrthosiphon churchillense new species from Oxytropis hudsonica (Greene) Fern, Aphis madderae new species from Taraxacum lacerum Greene, Capitophorus hudsonicus new species (collected by sweeping), and Macrosiphum subarcticum new species from Epilobium angustifolium L. It is suggested that Macrosiphum valerianae (Clarke) be declared a nomen dubium.

The baculovirus of Thymelicus lineola (Ochs.) has proved most effective as a microbial control agent of its host in numerous field trials, however, prior to its general use in an integrated control programme its possible deleterious effects on non-target organisms must be considered. Therefore the pathogenicity of this baculovirus to sheep and its cytopathogenicity to tissue cultures of lamb and calf testes were studied. Preliminary tests on 16 insect species were also carried out. No macro- or microscopic differences were detected between treated and control groups, suggesting that this baculovirus is quite specific and that its use as a microbial insecticide is feasible against T. lineola.

A stochastic model is developed for the expected number of prey taken by a single predator when prey depletion is apparent. The so-called “random predator equation” with prey exploitation of Royama and Rogers is compared with the stochastic model. The numerical comparisons illustrate situations where the deterministic model provides adequate and inadequate approximations.

Foliage on potted trees or cut branches of western larch, Larix occidentalis Nutt., served as food for rearing Coleophora laricella (Hbn.) during winter and spring. Potted trees were induced to flush by laboratory simulation of fall, winter, and spring to provide foliage the year around. The treatment was 2 months at a short-day photoperiod (SD = 12-h light: 12-h dark), followed by 2 months of darkness at 2 °C, then growth in a greenhouse at long day (LD = 18-h light: 6-h dark). C. laricella could be collected from the field for further rearing during much of the year. Year-round availability of all stages, however, was realized by rearings starting from laboratory-mated moths and eggs laid on potted trees. To promote continued development to the adult stage, a SD-LD-SD sequence of 6 weeks – 2 weeks – 3 weeks duration, then LD was imposed.

Last-stage larvae of Coleophora laricella (Hbn.) were transferred to foliated Larix occidentalis Nutt. trees in four stages of growth for feeding. Based on insect survival, development rate, and size, trees with newly flushing foliage were best for rearing; trees which had completed shoot elongation were nearly as favorable. Both were distinctly superior to trees with elongating shoots and to trees with foliage so old that the current year’s buds were breaking. It is important to recognize the effects of tree growth stage when rearing C. laricella parasites in the laboratory, because parasite survival and sex ratio can be significantly influenced.

Populations of potato leafhopper nymphs were sampled in two alfalfa fields throughout the summers of 1976 and 1977 in Montgomery County, Virginia. A dichlorvos-carton sampling method was used to collect nymphs from 3-stem alfalfa bouquets. Instars were based on head capsule measurements. The spatial distribution of nymphs generally fit the negative binomial model. Based on this distribution pattern optimum sample sizes were computed. The nymphal population can be reliably estimated within 20% c.v. during most of the alfalfa growth period. Although most variation was shown to be between samples and not between areas in the field, samples should be taken at random over the entire area of the field under study.

Typhlocyba pomaria McA., with two generations per year, damages the leaves and defaces the fruit of apple. It was reduced in numbers in an experimental orchard by the predatory mirid Blepharidopterus angulatus (Fall.) which attacked the second generation. The cold-hardiness of T. pomaria and B. angulatus overwintering eggs, which had mean freezing points of −35 °C and −34 °C respectively, was sufficient to protect these species from winter low temperatures in Nova Scotia.

When a few large trees are to be sampled, emergence traps provide more reliable counts of mites that are phoretic on southern pine beetles than either removal of bolts or removal of 100 cm2 bark discs. When a large sample from smaller trees is required, removal of bolts is preferable to removal of disc samples. Emergence traps or bolt samples are preferable to disc samples because: (1) fewer mites are lost during transportation and rearing; (2) mites are not left on the xylem; (3) fewer die from desiccation during rearing; and (4) fewer non-phoretic stages accumulate in the collecting medium.

Sympiesis yuekseli n. sp., a larval parasite of a new species of Phyllonorycter Hbn. from Burnaby, British Columbia, Canada, is described and illustrated.

A simulation model is described for the population dynamics of the European red mite, Panonychus ulmi (Koch). The model incorporates the following features: (a) development rate is dependent on effective daily temperature; (b) division of each population component into distinct daily age classes; (c) emergence of individuals from each population component is dependent on a log-normal probability distribution, and a temperature related development vector to accumulate a measure of the temperature effect on development. Validation runs on a mini-computer in 1976 and 1977 adequately described actual population curves determined from daily orchard sampling. A model of this type which can be used with small computers should prove useful in investigating the main factors affecting the population dynamics, and control strategies for this and other pests.

Adult emergence curves of the Nantucket pine tip moth, Rhyacionia frustrana (Comstock), and 27 members of its parasitoid complex were compared for four generations in the Georgia piedmont. Based on numbers of emerging adults, parasitism of the three 1975 R. frustrana generations was 42%. Two parasitoids, Lixophaga mediocris Aldrich and Compoplex frustranae Cushman, comprised 45 and 23% of all parasitoids, respectively.

Emergence curves of R. frustrana and parasitoids showed considerable overlap. It appears unlikely that foliar applications of broad spectrum insecticides for control of R. frustrana can be timed to prevent heavy parasitoid mortality.

Eleven species of parasitoids were reared directly from host larvae or pupae. Examination of host remains showed that some species of parasitoids may be either primary or secondary. The habits of Haltichella rhyacionae Gahan and Spilochalcis flavopicta Cresson were found to be more diverse than previously reported and include internal secondary and primary parasitism, respectively.