Three species of Hymenoptera comprise the guild of parasitoids utilizing alfalfa weevil, Hypera postica, larvae in Ohio. Where all three coexist, there has been a yearly increase in parasitization by Bathyplectes anurus and concomitant decreases in Bathyplectes curculionis and Tetrastichus incertus. We conclude that B. anurus dominance is due to its precise synchronization with peak host numbers, its high reproductive capacity, competitive superiority, and rapid search and handling. Domination of ephemeral hosts by such a parasitoid is in agreement with the general conclusions of Force, and Ehler and van den Bosch. B. curculionis and T. incertus compensate for imperfect synchrony with multivoltism and vagility (both spp.), aggregation and rapid search (B. curculionis), or random search and gregarious development (T. incertus).

A key is given for 37 species of Aphis L. in Manitoba. Three new species of Aphis are described, duckmountainensis, neomonardae, and whiteshellensis. Aphis monardae Oestlund is declared to be a synonym of A. gossypii Glover. Lectotype and paralectotypes are designated for A. rubicola Oestlund. Comments on taxonomy and biology are given for other species in the genus.

Adult and puparial keys are presented for five Microdon species occurring in eastern Washington and northern Idaho. The original description of Microdon cockerelli Jones is revised, and a new species of Microdon is described.

The only confirmed host plant of Tingis ampliata H.-S. (Tingidae: Heteroptera) is Canada thistle (Cirsium arvense (L.) Scop.). For this and other reasons, T. ampliata appeared to be a promising biocontrol agent for use in Canada. However, in the laboratory, T. ampliata developed fertile eggs while feeding on the two economic plants globe artichoke (Cynara scolymus L.) and safflower (Carthamus tinctorius L.), and nymphs developed to adults on globe artichoke. Therefore, T. ampliata should not be released in Canada.

Ethanol and sulcatol (6-methyl-5-hepten-2-ol), primary attractant and population aggregation pheromone, respectively, for Gnathotrichus sulcatus, were deployed alone or in combination on stumps and felled trees in the University of British Columbia Research Forest, Maple Ridge, B.C. On 18 April 1974, four Douglas-fir trees were felled at each of three locations, and four western hemlock trees were felled at each of three other locations. Felled trees and their respective stumps were baited on 26 April. Attacks by G. sulcatus and bark beetles were recorded at weekly intervals until 25 October. G. sulcatus attacks increased rapidly, reaching a maximum in June and July, followed by a steady decrease to October. Attacks by Dendroctonus pseudotsugae, Pseudohylesinus nebulosus, and P. tsugae showed characteristic seasonal trends, but were not correlated to any of the treatments. Over half the G. sulcatus attacks were on stumps, in which attack densities reached 683.5/m2. The greatest numbers of attacks were on stumps and logs baited with sulcatol or sulcatol plus ethanol. There was a significant interaction between sulcatol and ethanol on Douglas-fir but not on western hemlock. Significantly more G. sulcatus attacked ethanol-baited western hemlock stumps and logs than unbaited controls. However, there was no difference between the level of attack on ethanol-baited Douglas-fir and the controls. The role of ethanol is hypothesized to be more of a boring stimulant than a major attractant. Stumps baited with sulcatol and then treated with ethanolic solutions of systemic insecticide could be used to trap and kill field populations, thus reducing numbers of G. sulcatus being transported to log-booming grounds, dryland sorting areas, and sawmills.

An energy budget was evaluated for the bertha army worm, Mamestra configurata (Walker), over its life cycle. Cumulative values for the budget at the end of larval development were: ingestion, 2124 cal; respiration, 372 cal; production, 485 cal; and egestion, 1266 cal. The sixth instar larva accounted for 80.1, 83.2, 81.3, and 78.8% of the total energy in ingestion, respiration, production, and egestion, respectively, during its development. Assimilation efficiency varied from 35.5 to 44.4% with a mean of 40.6%, gross production efficiency varied from 16.6 to 23.8% with a mean of 21.3%, and net production efficiency varied from 37.5 to 61.3% with a mean of 52.7%.

In northern California Parargyractis confusalis has two to three generations per year, depending on climatic conditions. Adults lead a terrestrial life, though the female re-enters the water to oviposit. The eggs, larvae, and pupae exist underwater and have been collected to a depth of 4.3 m. Larvae occur in lakes and streams and are most abundant in areas where the water velocity is between 0.4 and 1.4 m/sec. Factors influencing the distribution and density of this species include water temperature, concentration of dissolved oxygen, substrate texture, and algal growth.

The structure and behavior of a sterile male intergeneric hybrid tenebrionid beetle from the Namib Desert are described. Compared with the courtship performance of males of the parental types the hybrid male was intermediate in choice of females. The parental species occur together in the field and there is a broad habitat overlap in utilized parts of the environment. Intergeneric courtship was regularly observed, but only one instance of hybridization was noted.

The adult female and male, deutonymph, protonymph, and larva of Macrocheles praedafimetorum n. sp. are described from bumble bee nests in southern Alberta, Canada. The new species appears to be a member of the glaber species-group. Various demographic characters are indicated. This mite exploits saprophagous organisms commonly found in dung, decaying matter, or bumble bee nests and has no effect on bumble bee populations.

Adults of Gryllus rubens Scudder, G. firmus Scudder, and G. ovisopis Walker were collected for 4 years from plots disked annually on one of six dates and from undisturbed plots to examine effects of date of soil disturbance on field cricket populations. Adults of the two field-inhabiting species, G. rubens and G. firmus, were most numerous from plots disked in February or April and least numerous from the plots disked in October and from the undisturbed (control) plots. Adults of G. ovisopis, a species that normally inhabits forests, were most numerous from the undisturbed plots and least numerous from the plots disked in August.

Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), populations were studied on white fir at four areas in central Sierra Nevada mountains of California during 1971–73. Life tables were constructed for four populations in El Dorado County. The number of eggs per egg mass decreased and the percentage eggs parasitized doubled with declining moth populations. Hymenopterous parasitoids were collected from all immature stages of the moth: one egg parasitoid, Telenomus californicus Ashmead, six species of larval parasitoids, principally, Hyposoter sp., and 13 species of larval–pupal parasitoids. Tachinids were predominant and accounted for 73% of the parasitoidism of the cocoons in 1971. The apparent mortality of female pupae due to the parasitoid complex was greater than 97% in 1971 and 75% in 1972. One population in Placer County collapsed in 1971 apparently due to a combination of heat exhaustion and low levels of virus infection. Other defoliators, spiders, and several predatory insect species were collected from the foliage samples simultaneously with the tussock moth during larval sampling. Twelve species of "free living" spiders which could be capable of preying on the defoliator complex of white fir were collected. Parasitoids and predators appear to be potentially important biotic factors at low to moderate host population levels. This is the first recorded case where an agent other than the nucleopolyhedrosis virus has been responsible for the collapse of a Douglas-fir tussock moth population.

Athrycia cinerea (Coq.) is a univoltine parasite of bertha armyworm, Mamestra configurata Wlk., on rapeseed in the Prairie Provinces of Canada. Details of the parasite’s seasonal life history are presented. Females oviposit on third, fourth, fifth, and sixth instars of bertha armyworm, and the parasite larvae usually develop gregariously and mature on the fifth and sixth instars. Supernumerary parasite larvae on superparasitized hosts starve; surviving larvae develop more rapidly, form smaller pupae with a lower capacity for survival, and eventually produce a consistently though not significantly smaller percentage of female adults than parasites that develop on non-superparasitized hosts. Larvae of A. cinerea are often killed if they compete with larvae of Banchus flavescens Cress., the only other common parasite of bertha armyworm, and a small percentage of the pupae of A. cinerea are killed by a hyperparasitic ichneumonid, Phygadeuon subfuscus Cress.

One female of Eusimulium rendalense Golini and three of E. fallisi Golini, among nearly 470 simuliids captured from Anas boschas L. in Norway, were found naturally infected with mermithid nematodes Two of these infected flies had fully fed on avian blood. The nematodes may be a species of the Gastromermis boophthorae complex Welch and Rubzov.

Observations on the nuclear polyhedrosis viruses affecting six different insects are reported. Of these, one has not been previously reported, and three others have had only minimal mention in the literature with no details given. In this paper, the viruses are illustrated by electron micrographs. The dimensions of the virus particles and other pertinent details are reported.

Several predator–prey models are examined to assess the generality of Volterra’s contention that an external mortality imposed simultaneously on both predators and prey results in a decrease in predators and an increase in prey equilibrium numbers. The models indicate that this phenomenon occurs mainly as a result of the lack of predator crowding. If predator crowding occurs, a strong functional response of predators to prey density, or light prey mortality relative to predator mortality, is required for Volterra’s phenomenon to occur. In increasing populations away from equilibrium, numerical results indicate conditions for Volterra’s phenomenon to occur.