g BULLETIN 720, U. S. DEPARTMENT OF AGRICULTURE. 
cordata); of thalia, a plant related to the cannas; of saltbush, water 
crowtoots, water milfoil, and mermaid weed; water hemlock; and of 
Spanish needle, pr bur marigold. 
Anrwat Foon. 
The animal food of the mallard duck though extremely varied 
may be classed in five main groups: Insects, which constitute 2.67 
per cent of the total diet; crustaceans, 0.35; mollusks, 5.73; fishes, 
0.47; and miscellaneous, 0.25 per cent. 
INSECTS (2.67 PER CENT). 
The mallard’s attentions to insects are divided about equally 
among beetles, bugs, and dragonflies, which together constitute 1.4 
per cent of the total diet. All other insects make up 1.27 per cent. 
As would be expected, the beetles eaten are mostly denizens of the 
water. They include among others both larve and adults of the 
crawling water beetles (Haliplide), small spotted beetles, most often 
seen among alge and other aquatic plants. Twenty different kinds 
of predacious diving beetles (Dytiscide) also were identified, both 
adults and larve being taken. The latter, so voracious that they 
have earned the name water tigers, are very destructive to other 
water-dwelling creatures and are a pest in fish ponds. Two partly 
predacious groups, the water scavenger beetles (Hydrophilide) and 
the whirligig beetles (Gyrinidz) also are preyed upon by the mallard. 
Among other beetles included in the dietary are ground beetles 
(Carabidz), which are chiefly useful; and leaf beetles (Chrysome- 
lide) and weevils, which are injurious. Of the leaf beetles, a group 
(Donacia) occurring in the mallard’s habitat, and naturally fed upon, 
live upon waterlilies. The adults rest on lily pads or skip about on 
the water surface; the larve live in tough cocoons on the lily stems, 
from which they secure both food and oxygen. One of the weevils 
identified in the food is the rice water weevil, a pest to cultivated rice. 
The bugs (Hemiptera) eaten by the mallard are practically all 
aquatic forms. They include water boatmen (Corixide), hundreds 
of which have been found in a single stomach; back-swimmers 
(Notonectide), water scorpions (Nepide), giant water bugs (Belos- 
tomatide), creeping water bugs (Naucoride), and water striders 
(Veliide and Gerridz). All these bugs are predacious, but whether 
they do more good than harm is a question, as many of them prey 
upon small fishes. Besides the Hemiptera already mentioned, a 
variety of other bugs occasionally are devoured by the mallard. 
Dragonflies, or snake-feeders, are active and expert insects on the 
wing, but in the younger stages they live in the water, where many of 
them fall a prey to the mallard. No fewer than 100 dragonfly 
nymphs have been found in one mallard’s gizzard, and from 30 to 40 © 
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