FOOD HABITS OF SHOAL- WATER DUCKS. 47 



ing water bugs (Naucoridae), of which the small, flat, predacious 

 bugs of the genus Pelocoris had been taken by 43 of the ducks; the 

 giant water bugs (Belostomatidae), represented by the genus Belostoma 

 in 37 stomachs; water striders (Gerridae), found in 30; back-swimmers 

 (Notonectidae), in 20; and water boatmen (Corbridae), in 15. Bugs 

 of the last three families mentioned are without exception very 

 active in their movements on or in the water, and their presence 

 in so many stomachs of the wood duck no doubt is accounted for 

 by their great abundance in lakes and rivers throughout most of 

 North America. One wood duck taken at Aid en, Wis., in August, 

 1908, had been feeding upon a species of plant louse (RJiopalosi-pJium 

 nymphaeae) which in certain states of its development inhabits the 

 leaves of waterlilies. The bird's gizzard contained about 1,600 of 

 these plant lice, as well as other insects and seeds. 



BEETLES (COLEOPTERA), 1.02 PEE. CENT. 



Beetles of at least 15 families were represented in the food of the 

 wood ducks examined. Of these the water scavenger beetles (Hydro- 

 philidae), predacious diving beetles (Dy tiscidae) , and leaf beetles 

 (Chrysomelidae) were most commonly taken. The first two families 

 mentioned, as their names imply, are strictly aquatic, while the third 

 was represented almost entirely by beetles of the genus Donacia, many 

 of which feed upon aquatic plants, such as the pondlily, spatterdock, 

 etc. Twenty-three of these beetles (Donacia cincticornis) were found 

 in one stomach, together with a large number of seeds of the tuberous 

 white waterlily (Castalia tuberosa), the plant on which they probably 

 were captured. Two other strictly aquatic families, the whirligig 

 beetles (Gyrinidae) and crawling water beetles (Haliplidae) were well 

 represented. Six genera of ground beetles (Carabidae) were identi- 

 fied, and the leaf chafers (Scarab aeidae), long-horned beetles (Ceram- 

 bycidae), and snout beetles (Curculionidae) had been eaten in con- 

 siderable numbers. The fact that scarabaeid beetles have been eaten 

 is often detected by the presence of small, hard grinding plates from 

 their jaws, which frequently persist in bird stomachs long after all 

 other parts of the beetles have been digested. Peculiar little silken 

 cases containing eggs of water scavenger beetles, usually attached to 

 a submerged leaf or to the body of the female beetle herself, are not 

 infrequently found in duck stomachs. In two from Louisiana they 

 made up 70 and 77 per cent, respectively, of the total contents. 



GRASSHOPPERS, CRICKETS, ETC. (ORTHOPTERA), 0.23 PER CENT. 



Grasshoppers of the genus Orchelimum were found in the stomachs 

 of 11 wood ducks from Missouri; 39 mandibles, representing at least 

 20 grasshoppers, were present in one stomach; 8 wood ducks had 

 eaten grouse locusts (Tettiginae). 



