50 Bulletin Wisconsin Natural History Society. tVol.-10, Nos. 1 & 2. 
were upon the substance they are feeding upon, crawling along 
the main stem of the plant and cleaning the branches of food by 
gnawing it away as they progress. Thus they may have more or 
less of a symbiotic relation to the plants upon which they feed. 
In detecting their food they depend largely upon chance collisions 
with it. When an animal comes in contact with a food particle 
the antennae immediately wave to and fro and finally rub against 
the object. The food is then grasped in the gnathopods and eaten. 
An animal may detect food without coming into direct contact 
with it, but it never detects food at any considerable distance, 
twice the length of the first antenna being the maximum distance 
observed. When their hunger is satisfied, they crawl in among 
the branches of the plant, or in the mud, remaining quiet, unless 
disturbed, until hunger drives them to activity for obtaining food 
again. Excepting protozoa, animal matter is probably not taken 
as a regular diet in their natural habitat, but they will eat it occa¬ 
sionally. If a piece of raw beef is dropped into an aquarium con¬ 
taining Hyalellce, it is but a few minutes before several of them 
will be found eating it. They act similarly with a piece of raw fish, 
though not to such a marked degree as with beef. Or if a portion 
of another Hyalella is offered them on the point of a needle, they 
will frequently display cannabilism and will eat from the offered 
morsel. Decayed flesh, which is a favorite diet of many other 
Crustacea, does not appear to be relished by Hyalellce. They make 
no attempt to capture prey, and probably they would be unable 
to succeed if they did attempt it. Animal food other than proto¬ 
zoa, probably enters into their diet only when they chance to 
encounter freshly killed flesh. 
ENEMIES. 
Fishes, birds, and predacious insects include all the enemies 
of Hyalella. They form an important article in the food supply 
of certain ducks and shore-birds ( Anseres and Limicolae) and of 
several fishes belonging to widely separated families. Of ducks, 
the Shoveller, Spatula clypcata (Linn.), is the principal enemy 
arid it consumes large numbers of aquatic amphipods, a majority 
of which are Hyalellce since it feeds almost entirely in the shallow 
waters of inland lakes and marshes. Forbes ( ’88, pp. 486 and 
527) in a summary of the results of his studies upon the food of 
