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Bulletin Wisconsin Natural History Society [Vol. 13, No. 1 
II. VARIATION OF FOOD WITH HABITAT 
The examinations showed that some fish changed their food 
as they grew larger, others stuck to one diet. Some ate the same 
food in all habitats, while others changed the food with varying 
environment. Different species of fish captured in the same habi- 
tat were found to have selected specific diets from the available 
rations provided by nature. 
Three cases of change of food with increase in size were noted. 
In a single lot of twenty Labidesthes sicculus collected on August 
7 at station 1, the ten largest individuals (max. length, 50 mm.; 
min. 38.2; ave., 41.2) had eaten 38.5% Cyclops and a trace of 
plants, whereas the ten smallest (max., 25.5; min., 18.4; ave., 
22.6) had eaten 1.7% Cyclops and 44.4% algae and seeds. Lepomis 
pallidus as it grew larger (21.3-35.3 vs. 36.0 to 57.0 mm.) ate 
less Cyclops and more Hyalella. In the collections from station 
11 on October 6, the smaller sticklebacks, Eucalia inconstans, 
ate more Chydorus sphaericus than larger individuals which had 
taken Cyclops instead. 
In most species where a large number was examined it was 
found that there was considerable variation in food with changes 
in habitats. In the following examples the largest single item 
in the dietary is mentioned in each case. Umbra limi ate largely 
ostracods (40%) at station 10, but had turned more to insect 
larvae (33.9) at station 11. Lepomis pallidus had great adapt- 
ability as the results from the following stations show: 1, 63.9% 
Cladocera; 2, 49.9 Hyalella; 5, 41.9 Cyclops; 8, 83.7 insect larvae. 
Perea flavescens gave the following- figures : Station 5, 33% dipter- 
ous larvae; 6, 57.7 Hyalella; 7, 96.2 Daphnia hyalina. Fundulus 
majalis menona was quite variable in its food habits having eaten 
at station 3, 55% Cladocera; 6, 35 Cladocera; 8 (August), 63.8 
ostracods; 8 (September), 30.8 vegetation. Labidesthes sicculus 
vacillated between adult insects and Cladocera. This species 
was using the former at stations 3 (99.5%) and 8 (69.5), the latter 
at stations 1 (31.1) and 6 (53.5). Notropis heterodon ate more 
Cladocera than anything else at stations 3 (62.4%) and 7 (August 
5-50.8%), but the guts of those collected at stations 4 (58.1%), 
5 (98.8), and 7 (August 17 — 44%) were filled with particles of silt 
and mud. Micropterus salmoides at different times fed largely 
