The 40 known species of the genus Xysticus C. L. Koch that occur in Canada are described and illustrated. Keys to both sexes are provided. Three new species, X. ampullatus, X. leechi, and X. winnipegensis, are described, two species, X. lutulentus Gertsch and X. nicholsi Gertsch, are synonymized with previously described ones, and two, X. ellipticus new name and X. alboniger new name, are transferred to Xysticus from another genus.

A series of laboratory toxicological experiments using various concentrations of oil formulated DDT solutions (AR-50/fuel oil (2:7 V/V)) was carried out on 5th and 6th instar spruce budworm larvae collected in the field from DDT-sprayed and untreated areas of New Brunswick, Canada, and Maine, U.S.A.

Results obtained in 1959, 1961, and 1962 with larvae collected from isolated, unsprayed areas in New Brunswick showed a consistent, straight log-dosage probit mortality curve. Larvae collected in 1962 and 1963 from infestation centres previously subjected to three, four, and five applications of non-consecutive large-scale aerial sprays of DDT showed a significant departure from the straight log-dosage probit curve previously obtained. The departure occurs as a change in the shape of the curve as well as a shift to the higher concentration range of DDT. The magnitude of change appears to be correlated with the number of sprays to which the population was exposed. Results obtained in 1962 and 1963, from untreated control and inter-spray areas, bounded by DDT-sprayed forest lands, showed a small but significant departure from the normal straight probit line of a susceptible population. These changes are indicative of a progressive development of DDT resistance in wild populations of spruce budworm.

Studies on the effect of the tolerance of spruce budworm larvae within instar classes to the action of DDT showed that the early phase of instar development immediately after moulting is more susceptible to the action of DDT, whereas the latter phase of instar development immediately prior to moulting is more tolerant to topical application of DDT than the average for the instar. This effect is evident in both susceptible and resistant populations.

The data interpretation assumes that a deviation from the straight line probit dosage – mortality curve is indicative of a difference in the DDT-susceptibility factor of the budworm population and that in the course of the tests, the amount of toxicant causing mortality was not proportional to the dosage.

The subgenus Cullumanobombus is represented by Bombus rufocinctus in the Nearctic region. In southern Alberta, its distribution is confined to the wooded areas. There, it is adaptable in its nest-selecting habits, and establishes nests mostly in June. It made 11.2 ± 1.4 cells in the first brood. In each cell, one egg was laid in the first brood, 4.2 ± 1.2 eggs in the second and third, and 8.2 ± 3.9 in the fourth and later broods.

Queens required about 22 days to rear workers. The second and third broods were usually workers and the fourth and later broods usually males or queens. The workers in a colony varied little in size. The dominant color pattern was B. rufocinctus s. str. This species is a prolific producer of wax.

The queens mated in the morning and hibernated in the afternoon, about an inch deep in the soil.

Many queens invaded other nests of the same species. The natural enemies were the three species of Psithyrus indigenous to the area, the big-headed fly, Physocephala texana, and ants.

In Nova Scotia one leaf cluster with an adjoining 1 inch of twig taken from the inside of each of 10 apple trees replicated four times is an adequate sample unit to measure the density of the brown mite.

The brown mite has one generation with a partial second in some orchards and one with a partial second and partial third in others. The first generation adults in the bivoltine and trivoltine populations lay summer eggs on the leaves and twigs, and diapause eggs on tin twigs. The second generation adults in the bivoltine populations lay only diapause eggs; in the trivoltine populations they lay both summer and diapause eggs. The adults of the third generation lay only diapause eggs.

The brown mite is found on both the leaves and woody parts of the tree. In orchards with bivoltine populations the proportion of mites on leaves reached a peak of 80% by mid-July, but thereafter gradually decreased to 10% by the end of August. However, in orchards with trivoltine populations the proportion of mites on leaves reached a peak of 80 to 90% by mid-July, remained constant until mid-August, and thereafter decreased to approximately 40% by the end of August.

The number of diapause eggs laid by adults of each generation in both the bivoltine and trivoltine populations varies widely. The eggs are deposited on the trunk as well as on the branches, with the heaviest deposition in the central area of the tree. The diapause eggs laid by adults of the first generation are the last to hatch and those laid by the third generation are the first to hatch the following spring.

The factors responsible for the differences in the number of generations and in the number of diapause eggs laid are unknown.

Mycophila speyeri Barnes is presently the most important mushroom-infesting cecid fly in Pennsylvania. Larval paedogenesis is the main means of reproduction (used by this species). Adult cecid fiies and sexual reproduction arc rarely observed in mushroom growing houses. The higher temperatures of spawn-run (70 ° to 75 °F.) are very favorable to paedogenetic reproduction of M. speyeri. Under these conditions, a generation is completed in about one week and about ten daughter-larvae per mother-larva are produced. The quantity of malt in the culture medium, the age of the spawn, and strain differences in spawn also play roles in the length of a generation and the number of young produced by a mother-larva. The lower temperatures (55 ° to 60 °F.), normal during mushroom cropping, approximately triple the time required to complete a generation. Prevention of cecid infestations during the spawn-run and sanitation to prevent spread, once larvae are present, are important considerations in the control of M. speyeri. Adult cecid flies occur only when populations become crowded on old growing media.

In a creek northwest of the Gatineau Hills (Quebec) larvae of Chironomidae (Diptera) were found living in phoretic association with the immature stages of Perlidae (Plecoptera). The larvae were reared to the adult stage in the laboratory. Life pattern and morphological comparisons are made with other phoretic and parasitic forms of Orthocladiinae and with certain other genera, and it is concluded that the form represents a new genus and species of Orthocladiini, and has probably originated from the common ancestors of the genera Rheocricotopus, Paracricotopus and Microcricotopus. Detailed descriptions are given of the imago, pupa and larva of this insect.