The Relation of Mollusks to Fish in Oneida Lake 225 
Anax junius Drury. Thirteen specimens of this species 
had eaten the percentages of food shown below: 
Wialieseahn (ANN LCOLG:)) mio. Pettn he aries og op of yah ves sai ets 15 per cent. 
NM MET Tere vere Alsiaa ote eS h Merete «StS os mayer ti sens eyes 11 per cent. 
Crustacea (amphipods, nearly all Allorchestes dentata).. 11 per cent. 
LINSORUSL SB GkcS Coit Ae One Pi creo ctr 8 Ore bic case EME Sone pc ate 56 per cent. 
The nymphs were observed to attack crawfish three- 
quarters of an inch long. 
The vegetation-inhabiting species have a varied diet, 
which includes back swimmers (Votonecta), water-boatmen 
(Corsia), small crustaceans, such as Asellus and Allorchestes, 
thin-shelled mollusks, like Physa, coleopterous and dipterous 
larve, and the younger and weaker members of their own 
order. Anax junius has been known to eat young carp 
(Riley and Howard, 1888, p. 58) and Cordulegaster macu- 
latus young trout (Needham, 1901, p. 474). 
Nymphs of dragon-flies are largely eaten by some of the 
best game and food fishes. Forbes (1888, b, p. 485) found 
four species to feed on this diet, as indicated below: 
Crass pickerel ((Hsom vermicularis) .....-...- 55+ =: 25 per cent. 
Crapmem (LoMmoexistannuUlaris)). fysee ee cls Gite wales oi 10-15 per cent. 
Pirate perch (Aphredoderus sayanus)..........-.--. 10-13 per cent. 
Common perch (Perca flavescens):........0.2....5- 10-13 per cent. 
Needham (1901, p. 474) also records horse-fly larvee 
(Tabanide) as feeding on snails. The giant water bugs 
(Belostomide) feed upon young snails when young (Dim- 
mock, 1886, p. 71) and the Lesser Water Bug, Zarttha 
flumineum (Serverin, 1911, p. 103) occasionally uses mol- 
lusks as food; Weed (1889, p. 12) says, “ Univalve snails 
also occasionally contribute to the diet of this insatiable 
creature, as one was observed feeding upon a small snail 
with a spiral shell.” 
Dawson (1911, p. 14, after Tryon, 1882) says, “ The 
species of Perthostoma (Belostoma), an American aquatic 
hemipterous insect, eat large quantities of Lymnwa, Physa, 
and Planorbis, which they hold with the fore legs by folding 
between the thighs and tibize; even the larvee of this insect, 
8 
