40 Journal New York Entomological Society. [Voi. xxi. 



aquatic or semi-aquatic life. Of such the most completely aquatic 

 in habit are found among the snout beetles. Tanysphyrus lenince, 

 living on Lenina and perforating its leaves, Amalus myriophyUi, on 

 Myriophyllum, Phytobius velatus, on Potamogefon, and Stenopelmus 

 riifinasus on Azolla, are nearly all known in both the old world and 

 the new, living indifferently above or below the surface of the water, 

 as adults, and within the tissues of the plants as larv?e. The adults 

 cannot swim, but depend upon the current to float them from one 

 plant to another, and are protected by hydrofuge pubescence for such 

 voyages or for the times when oviposition requires their descending 

 below the surface. Their adaptation to an aquatic existence ends 

 there, and the controlling factor in their environment is really the 

 relation to the food plant. In the case of the larvje there is even 

 less modification, for as it derives its supply of air from the tissues 

 of the plant on which it feeds, there is no need of special respiratory 

 apparatus. In a very qualified way therefore we may include all 

 beetles feeding upon aquatic or palustral plants, principally because in 

 the adults we shall always be able to note some adaptive modification 

 of vestiture. Such beetles will include the species of the genus 

 Donacia, which feed on water lilies, pickerel weed, Sagittaria, and 

 various other aquatic plants and sedges, the name itself being derived 

 from Donax, a reed. In the case of those feeding on water lilies the 

 larvae feed on the rootlets three or four feet below the surface of the 

 water, being provided with sharp anal appendages for the better pierc- 

 ing of the air cells in the plant (not on the stems as has been stated). 

 I have found on roots dragged out of the mud at the bottom, leathery 

 cocoons, which in winter contain larvae and in early spring pupae, 

 from which the adults have later hatched. McGillivray has given ex- 

 cellent details and figures of these insects. Although the adults re- 

 main above the surface of the water and deposit their eggs on leaves 

 at the surface, the other stages are thus spent below the surface. 

 The allied genus Harmonia is even more aquatic than Donacia, it lives 

 on Potamogeton, goes below the surface to oviposit and has proved 

 capable in captivity of living submerged for many weeks. Brocher 

 has experimented with the European species which is provided with 

 the peculiar pubescence described above, as capable of maintaining a 

 thin sheet of air about the body, thus permitting the insect to remain 

 long below the surface instead of resting on aquatic foliage like 



