AQUATIC INSECTS. 



By R. MathesOiV, M. S A , Ph. D. 



Although water in the form of lakes, ponds, and streams forms 

 a very considerah e portion of our continents, yet comparatively 

 little attention lias been paid to the aquatic environment as com- 

 pared with the terrestrial. Yet nowhere else does one find such 

 wonderful organisms, both plant and animal. It was onh^ after 

 the invention of the micro.«2 pe and the later appearance of Dar- 

 win's famous "Origin of Species" that naturalists turned their 

 attention to the study of aquatic organisms. The microscope aid- 

 ed in their study while the "Origin of Species" furnished the 

 great thought that living organisms first appear(;d in the water. 

 Yet despite all these encouragements the intensive study of the 

 fresh- water environment has made but little progress. This is 

 ]mrticularly true of the insect life of the water. Our students of 

 entomology have too long devoted their attention to the mere 

 collection, listing and describing of species. This of course is 

 necessary work, but it should be only the beginning of more com- 

 plete studies. To the sadly neglected field of aquatic insects we 

 should therefore direct our attention. 



Insects are all primarily terrestrial. Adaptation to aquatic 

 environment is secondary and is found not in isolated orders or 

 families but practically in nearly all of the great orders of insects. 

 The evidence that adaptation to an aquatic environment among 

 insects is secondary is practically conclusive, and this adaptation 

 occurred not only onc(> but at least over a hundred times in widely 

 se]mrated families of insects. Comparatively' few insects are 

 aquatic. They are found only along the shores of fresh water 

 ponds and lakes and in streams. They have not invaded the 

 deeper waters and only a few rare forms are found along the sea- 

 shores, while but a single genus of water-striders (Halobates) is 

 found at sea, long distances from land. Despite their compara- 

 tively few numbers they exhibit the most wonderful variety of 

 adaptation to the new environment. Practically nowhere else 

 will the student of evolution find more wonderful examples of 

 special adaptations. The adaptations to environment are often 



