Interactions between Bacillus thuringiensis Berliner and Apanteles fumiferanae Viereck as mortality factors of the spruce budworm, Choristoneura fumiferana (Clemens), were investigated by placing parasitized and nonparasitized budworm larvae on foliage with and without spray deposits of a commercial formulation of B. thuringiensis. The effect of larval age (and, thus, the timing of spray applications) was examined by using peak third-instar and peak fourth-instar larvae. We demonstrated that parasitized larvae are more likely to survive exposure to B. thuringiensis because they feed less than non-parasitized larvae and are thus less likely to acquire a lethal dose of the bacterium. Bacillus thuringiensis nevertheless reduced parasitoid populations by 50–60% by killing their hosts before parasitoid emergence. This negative impact of B. thuringiensis on parasitoid survival was decreased when exposure of budworm larvae to spray deposits was delayed from peak third to peak fourth instar. The enhanced survival of parasitoids offset the lower mortality as a result of B. thuringiensis in the delayed sprays. We conclude that B. thuringiensis applied when budworm larval populations are at peak fourth instar or later would complement rather than interfere with the beneficial effects of A. fumiferanae. The implications for budworm management strategies are discussed.

An outbreak of western spruce bud worm, Choristoneura occidentalis Freeman, in the Blue Mountains of eastern Oregon, USA, was treated with helicopter-applied carbaryl. Effects on forest ants were determined from pre- and post-spray samples taken from replicated 0.75-ha sprayed and unsprayed plots. Arboreally foraging ants were sampled with sticky drop traps placed under trees. Ground-foraging ants were sampled from food-baited boards. During 8 weeks of sampling, 13 225 ants from seven genera and 19 species were collected. Seven species were known budworm predators. After spraying, ant species diversity decreased in sprayed plots. Post-spray foraging decreased in all plots, but the decrease was more rapid and pronounced in sprayed plots. Among ground-foragers, budworm predators were clearly affected by spraying. Arboreal foragers, nearly all budworm predators, showed a significantly lower foraging rate in sprayed plots. Varying effects on different species were noted. Overall ant foraging remained depressed for at least 6 weeks after spraying, long enough for budworm development to be completed. Reduced ant predation on sparse budworm populations after spraying may contribute to budworm resurgence.

Variation in tree height, number of attacks by the Sitka spruce weevil (= white pine weevil) (Pissodes strobi [Peck]), tree form, and stem defect were studied in a 15-year-old Sitka spruce (Picea sitchensis [Bong.] Carr.) provenance test near Sayward, on Vancouver Island, B.C. An aggregated spatial distribution of the attacks was found in the plantation. Average number of attacks, tree form, and total tree height varied significantly among provenances and among families within provenances in both light and severe infestation patches. The number of unattacked trees varied by provenance from 5 to 51%, but in patches of severe infestation it varied from 0 to 64%. The number of attacks per tree had a significant negative effect on tree height. However, at the same level of attack, some provenances grew significantly taller than others. Thirty, 19, and 51% of all trees were classified as having a good, medium, or poor form, respectively. Among provenances located in severe infestation patches, the percentages of trees having good form varied from 4 to 64%. The type of defect that formed after an attack (minor crook, major crook, or fork) varied by provenance. Aggregated weevil attack and genetic differences among provenances may have accounted for this variation.

A change in the feeding behavior between small and large larvae of gypsy moth, Lymantria dispar (L.), is an important part of the insect’s biology. This paper describes how to build a lighting system with incandescent and fluorescent light in the laboratory to induce a change in feeding behavior similar to the change that occurs in the field. The change in feeding behavior was observed on artificial “tree stems” constructed from 5-cm ABS plastic pipe and fitted with felt and cardboard “bark flaps”. On the day before pupation began, 85% of the population migrated down the artificial tree stems to seek shelter under the bark flaps; only fourth-, fifth-, and sixth-instar larvae were observed exhibiting this behavior.

The fifth-instar larva of Cochylis arthuri Dang is described and illustrated. Characters for separating it from the fifth-instar larva and pupa of Cochylis hospes Walsingham are given.

The susceptibility of first-instar cabbage maggot, Delia radicum (L.), to parasitism by seven strains or species of entomogenous nematodes was compared in Petri dishes lined with moist filter paper. The effective doses for 50% mortality (ED50) of the Mexican, Breton, and All strains of Steinernema feltiae Filipjev, of S. bibionis (Bovien), and of Heterorhabditis heliothidis (Khan, Brooks, and Hirschmann) ranged from 98 to 341 infective juveniles per host larva with overlapping 95% confidence intervals; the slopes ranged from 1.36 to 1.07. The DD136 strain of S. feltiae and the species H. bacteriophora Poinar were significantly less lethal with ED50 values of 1113 and 1719 nematodes per host larva, respectively. The addition of a thin disc of rutabaga into the test dishes increased ED50 values by a factor of 20 or more. Application of the Mexican strain of S. feltiae at 5 × 105 nematodes per plant to small caged field plots of rutabaga artificially infested with eggs of D radicum provided control similar to that with diazinon applied at 1.4 L AI per hectare. Practical control of D. radicum on rutabaga with entomogenous nematodes would require strains or species considerably more lethal than those tested here.

Bathyplectes anurus (Thoms.) has displaced B. curculionis (Thorns.) as the main larval parasitoid in populations of the alfalfa weevil, Hypera postica (Gyll.), in eastern Ontario. Following its belated spread to the Bay of Quinte dairy belt, it used a combination of r and K strategies to assert its superiority: a greater reproductive capacity, more rapid search and handling, and more aggressive behaviour. Also, it is not subject to encapsulation by the host and reduces direct competition with the entomopafhogenic fungus Zoophthora phytonomi (Arthur) by laying its eggs in older hosts that have a greater probability of escaping death from disease. Taken together, these factors have enabled it to perform better than B. curculionis and to displace it in the host–parasitoid community. Moreover, it may have the potential to stabilize weevil populations during years when the fungus is enzootic.

Chaetocnema concinna (Marsham, 1802), a European flea beetle, is reported for the first time from Canada. Preliminary collection data indicate that it may feed on the same host plants as in Europe. It has been collected to date in Prince Edward Island, Nova Scotia, and Maine.

Gyrinus cavatus sp.nov. (type locality: Floral, Saskatchewan, Canada), from across Canada, is compared with G. minutus Fabricius. The two species are broadly sympatric in the northern boreal and transition forests, but G. cavatus is more abundant southward into the northern United States. Therefore, the subgenus Gyrinulus Zaitsev is not monobasic, but has three species in North America, including G. rockinghamensis LeConte.

The 70 species of Platycheirus (including Carposcalis, Pyrophaena, and much of Melanostoma of North American authors) occurring in the Nearctic Region north of Mexico are revised. Twenty-three species are described as new and new names are proposed for two species. Eighteen new synonyms and 14 new combinations are proposed; one variety name is given specific status. Six palaearctic species are recorded from North America for the first time, and one nearctic species from Europe, for a total of 23 holarctic species.

The Eurasian noctuid, Calophasia lunula Hufn., was introduced into North America to control yellow toadflax, Linaria vulgaris Mill., and Dalmatian toadflax, L. genistifolia ssp. dalmatica (L.) Maire and Petitmengin. Larvae feed on the foliage of both toadflax species, but different strains of the moth appear to prefer either yellow or Dalmatian toadflax (Nowierski 1990). Calophasia lunula was first released against yellow toadflax in five Canadian provinces from 1962 to 1968 (Harris and Carder 1971). The moth has been established on yellow toadflax in Ontario since 1965, where it has defoliated up to 20% of the stems (Harris 1988). However, attempts to establish C. lunula on Dalmatian toadflax in Canada have been unsuccessful (Nowierski 1990). Initial releases of the moth in the United States were made in 1968 against both toadflax species with Ontario stock from yellow toadflax (Nowierski 1990). Since then, multiple releases of C. lunula have been made in six western states, including Montana (Story 1985), but until 1989 no establishment had been recorded on either toadflax species.