The group of species related to Rhamphomyia basalis Loew is characterized in the male by an enlarged femorotibial joint of the hind leg and usually by modifications of the femur or tibia or both, and in the female by broad, usually infuscated wings and more or less pennate legs.

Current investigations at the Forest Biology Laboratory, Winnipeg, are being directed towards the formulation of life tables for the larch sawfly, Pristiphora erichsonii (Htg.) (Lejeune, 1955). Because small mammal predation is a major factor in reducing cocoon populations of the sawfly (Buckner, 1953), an adequate method of assessing this source of mortality is desirable

Insect flight can be divided into four basic components which lend themselves to independent study. These are: (1) flight preparation and response; (2) the body movements and their resultant forces; (3) the flight capacity; and (4) flight orientation. Many authors have dealt with these various phases of flight and studies have been made on a wide variety of insects. Nevertheless, on reviewing the literature two deficiencies become apparent. First, there are very few cases where a complete study of flight has been made for a single species, an outstanding exception being the studies on locust flight by Weis-Fogh and Jensen (1956). Secondly, beetles, particularly the Scolytidae, have been neglected as experimental material in flight studies

The fluctuation of an animal's numbers between restricted limits is determined by a balance between that animal's capacity to increase and the environmenta1 cheks to this increase. Many authors have indulged in the calculating the propressive increase of a population when no checks nrerc operating. Thus Huxley calculated that the progeny of a single Aphis in the course of 10 generations, supposing all survived,would “contain more ponderable substance than five hundred millions of stout men; that is, more than the whole population of China”, (in Thompson, 1929). Checks, however, do occur and it has been the subject of much controversy to determine how these checks operate. Certain general principles—the density-dependence concept of Smith ( 1955) , the competition theory of Nicholson (1933)—have been proposed both verbally and mathematically, but because they have been based in part upon untested and restrictive assumptions they have been severelv criticized (e.g. Andrewartha and Birch 1954). These problems could be considerably clarified if we knew the mode of operation of each process that affects numbers, if we knew its basic and subsidiary components. predation, one such process, forms the subject of the present paper.