486 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
4959. Chiefly the small white Chironomus larvae, and pupae of the same, several 
examples of Allorcliestes^ a few nymphs of the genus Ephemera, a single Eurycercus 
lamellatus, and fragments of filamentous Algae, with some other vegetable particles. 
4960. A considerable quantity of the larvae and pupae of Chironomus already 
mentioned,— the former 9 to 10 millimeters long, — together with immature Ephemerae 
and fragments of filamentous Algae. 
4962. This specimen added to the usual Chironomus larvae and pupae which 
formed the greater part of the food, a few Allorchestes, a young larva of Ephemera, a 
Corixa larva, a small leech, and a single young Sphaerium. 
4963. Many specimens of Allorchestes dentata, a few caseworms with their sand- 
tubes, several nymphs of Ephemera, a considerable number of small chironomid larvae, 
aud two specimens of Cyclops. 
4964. Chiefly larvae aud pupae of the small Chironomus. Besides these a few 
caseworms and specimens of Allorchestes. 
4965. (From Third Lake.) Several of the usual small Chironomus larvae, a larva of 
Corethra, aud the mollusk Physa. 
4988. The stomach of this example contaiued only larvae and pupae of the small 
Chironomus. In the intestine, besides the above, there were two caseworms in their 
cases. 
(4) All the facts just cited tend to show that the perch perishing were ranging in 
the deeper water, and that they had almost invariably made their last meal of insect 
larvae found only in the mud of the deeper parts of the lake ; that they had been, in 
short, in company with the herring likewise notably diseased. I was informed by a 
fisherman familiar with the lake and its inhabitants that it was an extraordinary thing 
to find the perch ranging into deep water in midsummer, although they were frequently 
found in numbers in the depths of the lake in winter, when fished for through the ice. 
lu these winter specimens red “ worms” (Chironomus larvae ?) were often noticed. 
(5) The mud from the deeper part of the lake, as has been already mentioned, had 
a peculiar rank aud almost stinking odor, aud contained a considerable quantity of 
organic matter undergoing more or less rapid decay. 
(6) A comparison of my collections from Lake Mendota with those from Lake 
Geneva, reported in this article, and especially with my much more abundant collec- 
tions made from the lakes in northern Illinois, shows an unusually small proportion of 
cray-flshes, Aselli, Allorchestes, and other crustaceans ordinarily common in our lakes 
among the weeds and shallower waters generally, and a correspondingly large percent- 
age of Chironomus larvae iu the food of all the perch examined, — a fact which hints 
at the probable deficiency iu this lake of the kinds of insect larvae and crustaceans 
usually selected by the perch. 
(7) The weather of the summer had been warm and rather showery, but not in any 
way especially remarkable. There was, however, one heavy flooding rain not long be- 
fore the outbreak of the fish disease, which may well have washed into the lake unusual 
quantities of organic matter from the swamp beyond Catfish Bay and from the sur- 
rounding country. Any organic accumulations due to such an occurrence would neces- 
sarily have been more evident in Lake Mendota, the uppermost of the chain, and that 
with the largest drainage basin, than in any of the lakes below. 
(8) What seem, from the best information I can obtain, quite similar cases of 
destruction of our native fishes, are of rather common occurrence in the rivers of Illi- 
