Larvae of the larch sawfly, Pristiphora erichsonii (Htg.), feed on the foliage of conifers of the genus Larix. In Manitoba and Saskatchewan, where the studies described here were conducted, the native host is tamarack, L. laricina (Du Roi) K. Koch. At outbreak population levels larval feeding commonly causes complete defoliation. Trees show a marked reduction in foliage production after three or four successire vears af severe defoliation (6). As a consequence, larval starvation is commonly associated with declining host vigour. Starvation reduces the population size directly by causing larval mortality and indirectly by reducing the reproductive capacity of the partially starved survivors. This paper deals primarily with the measurement of the sub-lethal effects of starvation during the last larval stadium as studied in laboratory-reared and field-collected insects.

Among others, Schwerdtfeger, 1931, Gosswald, 1934, and Morris, 1949, have used frass-drop samples as indirect measurements of the density of forest insect populations with some success. The method has also been used to assess the effects of various insecticides on the feeding of treated larvae (Rhumbler, 1929; Schwerdtfeger, 1930) and to study the influence of weather upon the feeding and development of forest insects (Monro, 1935).

Nomada obscurella Fowler, 1902, was originally described from one male from Berkeley, California, March 18, from Ranunculus californicus, under the name N. obscura Fowler, 1899 (preoccupied). Nomada fowleri Cockerell, 1903, was described from a female from Corvallis, Oregon, April 15, 1897 (A. B. Cordley). In connection with a study of some interrelationships of some Ranunculus bees we have become convinced that the two are synonymous. Although in general we disapprove of the association of sexes by elimination, in this case we regard the circumstantial evidence so strong as to leave little doubt that they represent the two sexes of a strikingly sexually dimorphic species.

The common North American ant-lion, Myrneleon immaculatus DeGeer, is generally distributed throughout the United States and has extended its range northward into Canada at various places. Throughout its range, the regular, cone-like pits of larvae of this species inay be found in dry, sandy stretches that in an ecological sense constitute small, isolated desert regions.

Temperature is one of the most important of rhe physical factors with which desert species must contend. It is the purpose of this paper to present the results of gn investigation of the effects of temperature upon the behaviour and activity of larvae of M. immaculatus in their natural habitat.