PROCEEDINGS. 1917 21 



FOSSIL INSECTS, WITH SPECIAL REFERENCE TO THOSE OF 



THE TERTIARY LAKE DEPOSITS OF THE 



SIMILKAMEEN VALLEY, B.C. 



By .Alfred E. Cameron, M.A.. D.Sc, F.E.S. 



MEANS OF FOSSILIZATION 



Abundant as insects are at present, they are comparatively rare as 

 fossils, the fossil species forming a very insignificant percentage of the 

 total number of described species of insects. The absence of insect 

 remains in sedimentary rocks of marine origin is explained by the fact 

 that almost no insects inhabit salt water ; and terrestial forms, in general, 

 are ill-adapted for fossilization. The hosts of insects that die each year 

 leave remarkably few traces in the soil, owing perhaps in great measure 

 to the dissolution of chitin in the presence of moisture. 



Most of the fossil insects that are known have been found in vege- 

 table accumulations such as coal, peat, lignite, or else in ancient fresh 

 water basins, where the insects were probably drowned and rapidly 

 embedded. At present, enormous numbers of insects are sometimes cast 

 upon the shores of our great lakes — a phenomenon which helps to 

 explain the profusion of fossil forms found in some of the ancient lake 

 ' basins. 



Insects in rich variety have been foimd in amber, the fossilized resin 

 of coniferous trees. This substance, as it exuded, must have entangled 

 and enveloped insect visitors, just as it does at present. Many of these 

 amber insects are excellently preserved, as if sealed in glass. Copal, a 

 transparent amber-like resin from various tropical trees, particularly 

 Leguminosae, has also yielded many interesting insects. 



Ill-adapted as insects are by organization and habit for the com- 

 moner methods of fossilization, the number of fossil insects already 

 described is now more than 6000. 



LOCALITIES OF FOSSIL INSECTS 



The Devonian of New Brunswick in Canada has furnished a few 

 forms, found near St. John, in a small ledge that outcrops between the 

 tide-marks. These forms, though few, are of extraordinary interest, as 

 will be seen. 



For Carboniferous species, Commentry in France is a locality noted 

 through the admirable researches of Brongniart (6), who described from 

 there 97 species of 48 genera, representing 12 families or higher groups 

 — 10 of which are regarded as extinct — without including many hundred 

 specimens of cockroaches which he found but did not study. In this 

 country many species have been found in the coalfields of Illinois, Nova 

 Scotia, Rhode Island, Pennsylvania and Ohio. 



