I9g2 ENTOMOLOGY 
cluding the dragon flies, flies, bumble bees and wasps. Fora- 
ging Carabidze were observed in large numbers, also scaven- 
gers of the families Staphylinide, Silphide and Dermestidee. 
On the seashore and on the shores of the Great Lakes, the 
salient features of insect life are essentially the same. Sim- 
ilar species occur in the two places with similar biological 
relations, on account of the general similarity of environment. 
Origin of the Aquatic Habit.—The theory that terrestrial 
insects have arisen from aquatic species is no longer tenable, 
for the evidence shows that the terrestrial type is the more 
primitive. Aquatic insects still retain the terrestrial type of 
organization, which remains unobscured by the temporary and 
comparatively slhght adaptations for an aquatic life. Thus, 
the development of tracheal gills has involved no important 
modification of the fundamental plan of tracheal respiration. 
It is significant, moreover, that the most generalized, or most 
are without exception terres- 
primitive, insects—Thysanura 
trial. Aquatic insects do not constitute a phylogenetic unit, 
but represent various orders, which are for the most part un- 
doubtedly terrestrial, notwithstanding the fact that a few of 
these orders (Plecoptera, Ephemerida, Odonata, Trichoptera ) 
are now wholly aquatic in habit. Adaptations for an aquatic 
existence have arisen independently and often, in the most 
diverse orders of insects. 
