The costs and benefits of insecticidal control and the losses attributable to flea beetle damage are estimated for oilseed rapes in Canada. Analyses of two farm surveys and reports on the efficacies of the various control practices conducted in test plots led us to calculate three sets of estimates based on different assumptions. Four-fold differences are observed between the lowest and highest estimates. The lowest estimates are adopted as the most realistic. The estimated losses were $72 million in 1979, 8% of the annual production. In 1979 growers spent about $12 million on insecticidal control which saved about $44 million worth of production. We conclude that flea beetle damage to rape causes an average annual yield loss of about 10% and is higher in Manitoba than Saskatchewan. The damage levels estimated from small test plots are higher, on average, than those in commercial fields, which accounts for most of the differences among estimates.

Vairimorpha necatrix (Kramer) readily infects and kills the European corn borer, Ostrinia nubilalis (Hübner), in the laboratory. The corn borer is either killed in the larval stage within a few days after infection by disruption of the midgut and septicemia or in the pupal stage by microsporidiosis. Insects that are not killed by V. necatrix have a reduced potential for pupation, emergence, and reproduction.

Tipula paludosa spends increasing periods of time in a pharate condition with each succeeding molt. The pupa is entirely pharate since larval–pupal ecdysis coincides with pupal–adult apolysis, and the larger part of the adult instar is also spent in a pharate condition. The fact that the instar usually referred to as the pupa is actually a pharate adult should be clearly understood by physiologists, ethologists, and ecologists.

The gall fly Urophora cardui (L.) (Diptera: Tephritidae), native to Europe, was released at 24 locations across Canada beginning in 1974. It became established in Ontario, Quebec, and New Brunswick but died out in all but one location in western Canada. Evidence for winter mortality in the west does not explain the failure of these colonies. Although galls, in particular those on the main shoot, reduce the height of Canada thistle, so far the impact on the host weed, Canada thistle (Cirsium arvense) (L.) Scop., is slight.

Study of the Nearctic members of Brillia showed that one species, Brillia par (Coquillett), belonged to an undescribed genus. To establish a name for use in other publications brief descriptions of all stages of this new genus, Xylotopus, are given. Detailed descriptions will be presented later. The identity of the immature stages have been established by rearing. Terminology follows that of Saether (1980).

Electrophoretic characterizations of sibling species in the Simulium venustum–verecundum complexes are presented based on nine enzymatic loci. Simulium verecundum s.l. is easily separable from S. venustum s.l. by unique complements of electromorphs for lactate dehydrogenase. Quantitative and minor qualitative differences also exist between most pairs of sibling species within S. venustum and S. verecundum. Not all pairs are separable using the nine enzymatic loci scored in this study. This close genetic affinity of species pairs that are not separable by electrophoretic methods parallels their chromosomal and ecological affinity.

Camponotus modoc was associated with numerous species of Homoptera in Giant Forest, Sequoia — Kings Canyon National Park, California. Ant-exclusion experiments and field observations indicated that survival of the abundant Cinara occidentalis Davidson on white fir depends on attendance by C. modoc. More of the predators, Neomysia oblonguttata (Mulsant), Deraeocoris brevis Uhler, Passaloecus cuspidatus F. Smith, Pityophyphantes sp., were found on ant-unattended than on attended aphid colonies. As aphid populations decreased, ant attendance per aphid and number of predators/aphid increased. Attended aphid colonies were more likely to survive to produce oviparae and a lower proportion of alates.

In Saskatchewan the range of Phyllotreta striolata (F.), a pest of parkland rapeseed crops, includes the open prairie in the southwest and the boreal forest in the north. The population of P. striolata on the open prairie is small, with cruciferous weeds being the major host plants. Cruciferous crops grown on the open prairie will almost certainly attract some P. striolata. The population of P. striolata in the forest is substantial, and the range extends northward into arctic regions. Although adults of P. striolata feed upon cruciferous plants growing in the forest, these plants do not appear abundant enough to constitute an adequate food supply. In addition, the identity of the major host plants of the larvae in the forest is unknown. In laboratory experiments, adults of P. striolata were attracted to and attempted to feed upon seven species of forest mosses; however, attempts to maintain a laboratory colony of P. striolata on one of the more abundant mosses were unsuccessful. Forest inhabiting P. striolata attacked rape planted in forest clearings, and therefore probably would infest rape crops grown along the forest edge or in newly cleared areas.

Grasshopper populations were monitored for 2 years in six differentially grazed pastures of native shortgrass prairie, and correlated with floral biomass in these pastures. Total numbers of grasshoppers were significantly higher in high biomass pastures (ungrazed or lightly grazed by cattle), while numbers of grasshoppers in the subfamily Oedipodinae were significantly higher in low biomass pastures (moderately or heavily grazed). Grasshopper numbers in the phytophilous subfamilies Gomphocerinae and Catantopinae were positively correlated with grass and forb biomass, while numbers of the geophilous Oedipodinae were negatively correlated with all biomass components. It would seem possible to modify grasshopper abundance through regulation of cattle grazing intensity, but changes in abundance would also be accompanied by shifts in the grasshopper species complex.

Diapause development in Culex tarsalis Coquillett has been characterized by reduced blood-feeding to complete termination of ovariole development at or before stage IIa (Bennington et al. 1958; Schaefer and Washino 1970; Schaefer et al. 1971; Bellamy and Corbet 1973; Mitchell 1979). The role that diapausing Culex species have in overwintering arboviruses has been examined (Eldridge 1966, 1968; Eldridge et al. 1972; Reeves 1974; Eldridge and Bailey 1979; Mitchell 1979). Gonotrophic dissociation and its implications for survival of the vector and virus has been reviewed by Washino (1977). Eldridge (1966) indicated gonotrophic dissociation was possible in Culex pipiens L. incubated at low temperature and short daylength and later reported failure of ovarioles of prehibernating C. pipiens to mature following a blood meal (Eldridge and Bailey 1979). Eldridge et al. (1972) reported that Culex restuans Theobald exhibited gonotrophic dissociation in response to conditioning by short daylength and low temperature. Mitchell (1981) has reported blood-feeding and gonotrophic dissociation in a significant portion of diapausing Culex tarsalis from Colorado, when females were kept at 15°C and at short daylength conditions.

Three body dimensions (body length, head width, and abdomen width) were used to determine size differences between laboratory-reared and wild populations of Trichogramma minutum Riley. Six separate groups of T. minutum were measured: three groups were from Sitotroga cerealella (Olivier) eggs, two from spruce budworm Choristoneura fumiferana (Clemens) eggs, and one from wild populations of spruce budworm.

Female T. minutum from spruce budworm (large host) eggs were significantly larger for all body dimensions than T. minutum from S. cerealella (small host) eggs. Male T. minutum from field-collected spruce budworm eggs were significantly larger for all body dimensions than T. minutum reared for more than one generation in S. cerealella eggs.

A significant reduction in female parasitoid size was observed during the initial generations of T. minutum reared in the smaller host (S. cerealella). However, this size reduction was not permanent. Following numerous generations in the S. cerealella host eggs, a significant increase in female parasitoid size was noted within the first generation of T. minutum reared in the spruce budworm host eggs.

Plagiognathus ribesi n. sp. is described from British Columbia and Colorado. Psallus salicellus (Herrich-Schaeffer), an introduced European species earlier reported from Nova Scotia, has also been found to occur in Prince Edward Island and British Columbia.

Fifteen months after an intense forest fire, the fauna of carabid beetles in burnt and unburnt sites was sampled using pitfall traps to detect the indirect effects of fire on carabids caused by habitat change. Traps were installed in burnt and unburnt sites in which the dominant tree species before the fire was either spruce or aspen. The most commonly caught species was Pterostichus pensylvanicus which was captured more frequently in unburnt sites, but was not affected by dominant tree species; a similar pattern of distribution of captures was found for Carabus taedatus. Harpalus laticeps was captured only in burnt sites. P. lucublandus and Dicaelus sculptilis upioides were most commonly caught in the unburnt aspen site, while Pterostichus adstrictus was most commonly caught in the burnt spruce site.

Antipic, an electronic mosquito repeller, was evaluated in the field and in the laboratory. It was ineffective in repelling natural populations of mosquitoes (mostly Aedes spp.) in Ste. Anne de Bellevue, Quebec.

Since its initial introduction into North America (Saunders 1916) the European skipper Thymelicus lineola (Ochs.) has been found attacking timothy grass throughout much of eastern Canada and the United States reaching pest status in Ontario (Arthur 1966), Prince Edward Island (Thompson 1977), and Quebec (Doyle and Richard 1971; McNeil et al. 1975). Bucher and Arthur (1961) examined skipper larvae, collected near Princeville, Ontario, for naturally occurring pathogens and reported the presence of a nuclear polyhedrosis virus, a cytoplasmic polyhedrosis gut virus, and a spore forming bacterium. They stated that such pathogens represented a possible means of biological control if the skipper became economically important. An epizootic caused by an NPV in dense skipper populations near Normandin, Quebec (Smirnoff 1974), led to a series of experiments evaluating its efficacy as a microbial insecticide (Smirnoff et al. 1976; Duchesne 1980), its long term impact on the population dynamics of T. lineola (Duchesne 1980), and its possible effects on non-target organisms (Smirnoff et al. 1979).

Male and female laboratory reared spruce budworm moths, Choristoneura fumiferana (Clem.), were placed in cages in a conifer forest, and the surrounding air permeated by each of four blends of the E and Z isomers of the sex pheromone (11-tetradecenal) at two concentrations. Mating suppression of 53–83% was found for each blend tested. At one concentration the four suppressions were similar, while at the other only one was significantly different. Electroantennograms (EAGs) were obtained from male moths for each of six E:Z blends at four concentrations. EAGs were similar for most blends at a given concentration, but tended to be larger than at a blend of 0E:100Z.

These results were discussed using a current hypothesis on the ability of males to detect sex pheromone in air containing pockets of different isomeric blends.

Male moths of striped cutworm, Euxoa tessellata (Harris), were specifically attracted to blends of Z-5-tetradecenyl acetate or Z-5-hexadecenyl acetate with Z-7-hexadecenyl acetate. The most satisfactory quantities of these components per septum dispenser were: Z-5-tetradecenyl and Z-7-hexadecenyl acetates at 2.5 and 500 μg, or Z-5-hexadecenyl and Z-7-hexadecenyl acetates each at 500 μg. The addition of 1.0% Z-7-hexadecenol relative to Z-7-hexadecenyl acetate in either of these blends inhibited the attraction of males. The blend involving Z-5-tetradecenyl acetate is recommended for monitoring purposes.

Experiments were performed to determine the role of body weight in the response of last instar western spruce budworm, Choristoneura occidentalis Freeman, to a topically applied juvenile hormone analogue (JHA), Ro 13-5223 (Ethyl [2-(p-phenoxyphenoxy)ethyl] carbamate). The response of males in weight classes from 50 to 130 mg was not proportional to their body weight; susceptibility increased drastically in heavier larvae. The susceptibility of females increased in proportion to their body weight. The results of these experiments suggest that future investigations of JHA effectiveness in last instar Lepidoptera should consider both weight and sex as possible relevant variables. Age of the last instar may not, in itself, be an adequate measure by which to quantify JHA effects.

Within and between tree distributions of the Jeffrey pine needle miner, Coleotechnites sp. and its food resource (needles), were investigated on Jeffrey pine trees at three locations in the San Bernardino Mountains of southern California. These data were used to compare sample allocation by the component of variance technique and a method based on the mean crowding relationship. The numbers of samples necessary to estimate the mean at a given precision differed between the techniques in some cases. The mean crowding technique offered several advantages which are fully discussed. A sampling design for the Jeffrey pine needle miner is proposed.

The formerly monotypic genus Halidayina Duda, based on the Holarctic species H. spinipennis (Haliday) is revised. Two new species are described, H. exserta from Arizona and California, and H. asymmetrica from Mexico.