Investigations were carried out to determine the effect of ecological factors on the induction of diapause in the spruce budworm. Experimental rearings were conducted at elevations of 2500, 4200 and 4750 feet. The foliage of spruce, Douglas fir and alpine fir were used as hosts. Progeny of Ontario, two-year and one-year types reared under one-year and two-year life cycle conditions were used as experimental insects. A trend was observed in emergence from hibernation with the one-year type leading, followed by the two-year and finally the Ontario type. It was shown that the one-year type larvae may adopt the two-year habit. The main factor influencing this is a prolonged development period for the parents. The larvae reared at the higher elevations showed a greater proportion entering diapause. Food played a smaller role with spruce and Douglas fir being more favourable for diapause than alpine fir. The increased percentage of larvae in diapause in 1952 is attributed to a longer development period for their parents and to a sharp drop in temperature occurring about 12 days prior to diapause. The Ontario material may adopt the two-year habit. The factors contributing to this have not been clearly shown as the rearing results are inconclusive. There were no definite differences shown in the time for development among the three foods. The insects at the lowest station developed in approximately three weeks less time than at the highest. The difference between the upper stations was slight. The impracticability of converting a one-year life cycle population to a two-year cycle by forest management is noted. The diapause theories of Wigglesworth and Andrewartha are commented on. A possible course of evolution leading to the establishment of a two-year life cycle population is given. / Science, Faculty of / Zoology, Department of / Graduate

In the region of Lillooet, B.C. a small population of spruce budworm, Ohoristoneura fumiferana (Clem.), has maintained a relatively constant sub-epidemic level for several decades, feeding on Douglas fir, Pseudotsuga taxifolia (Poir.) Britt. No tree mortality has occurred. This population has been under observation for ten years, and it is apparent that an effective natural control complex is operating in the area. Spiders are prominent among the predators of insects in the region. Field observations revealed that many spiders captured both larvae and moths of the spruce budworm. A collection of arboreal spiders of the region was made and identified. Feeding tests were conducted with spiders to determine the budworm-feeding species. Both caged and free spiders were tested. Population samples were taken to determine the relative abundance of spider species in the area, and to discover any differences that may exist between spider populations in the infested forest and in the non-infested forest. Four families were found to comprise eighty percent of the arboreal spiders of the Lillooet district, and seventy percent consisted of only two families, the Thomisidae and the Salticidae. The Thomisids do not capture spruce budworm larvae, but may capture moths. The Salticids capture both larvae and moths. Families Argiopidae and Theridiidae occasionally capture larvae and frequently capture moths. No difference was demonstrated between spider populations in the infested forest and the non-infested forest. / Forestry, Faculty of / Graduate