﻿14 BULLETIN 1359, U. S. DEPAETMENT OF AGRICULTURE 



(Notonecta) were found 3 times and a form of water bug (Belostomat- 

 idse) once. Water-boatmen, identified in 23 instances, seem to be 

 standard article of diet, 



Coleoptera. — Beetles as a group constitute 11.4 per cent of the food. 

 Among them small shore-haunting ground beetles were common, 

 none known to be of economic importance. A few crawling water- 

 beetles (Haliplidse) were found and a number of predacious diving 

 beetles. Larvae of this latter group were identified 9 times. Water- 

 scavenger beetles in both adult and larval stages also were well repre- 

 sented. Weevils were as abundant as other groups of beetles and 

 included billbugs (Spheno'pJiorus) in 5 instances. 



Diptera. — FUes, amounting to 23.8 per cent of the total subsistence, 

 compose the largest single item in the animal food. Although abun- 

 dantly represented, the species taken belong to comparatively few 

 groups. Larvse of crane fhes (Tipulidse) were taken 4 times and larvse 

 and pupse of fhes that could not be certainly identified 5 times. The 

 immature stages of gnats (Chironomidse) were especially sought. 

 Individuals identified as belonging to the typical genus Chironomus 

 were found 6 times, and those of related forms, 11. Often many 

 were found in one stomach, though ordinarily so broken that they 

 could not be counted with accuracy. In a number of instances, how- 

 ever, it was ascertained that several hundred had been swallowed by 

 one bird. 



In the Great Basin region alkali fhes (Ephydridse) were favored as 

 food/ as they were not only palatable but abundant about brackish 

 or saline waters and in most cases easily secured. In spring and early 

 summer thousands of these flies are found gathered in close array on 

 expanses of soft, alkahne mud. Avocets run up hastily to such con- 

 gregations and strike at them with lateral sweeping motions that fill 

 their bills with them and with soft mud before the insects can escape. 

 At such attacks the fhes in limited areas rise in sudden swarms, but 

 others at a short distance remain quiet, so that by taking a few steps 

 the birds are able to make another attack on gatherings whose num- 

 bers have been augmented by the arrival of individuals frightened up 

 at the first onslaught. The larvse of these flies abound in many places, 

 especially in the strongly saline waters of the lakes characteristic of 

 the Great Basin. At Great Salt Lake many avocets after the nesting 

 season frequent shallow bays near the lake front, where these larvse 

 swarm, in order to feed upon them. 



Miscellaneous. — Snails are eaten occasionally by avocets and were 

 found in 6 stomachs, although they amount only to 0.8 per cent of 

 the total. The species are those common in shallow ponds and 

 marshes. Other miscellaneous items of animal food, 14.5 per cent, 

 include a varied assemblage of forms, none of which were present in 

 sufficient number to merit separate tabulation. Nymphs of May- 

 flies were found twice, and cases and other remains of caddisfly 

 larvse 3 times. Caterpillars were identified 3 times, and fragments 

 of small grasshoppers (Acridiidse), 4. The Hymenoptera were repre- 

 sented by single findings of ants, a larrid, a braconid, and one other 

 form not identified. Spiders were found in 2 instances. A small 

 chub (Leuciscus lineatus) had been eaten by one bird and an unidenti- 

 fied fish by another. Bones of a tiny salamander were encountered 

 in the stomach of one bird. 



