DRAGONFLIES AND DAMSELFLIES IN PONDFISH CULTURE. 229 
The number of fish included in this table is large enough to give considerable weight 
to the conclusions drawn; a thousand fish stomachs ought to furnish a fairly reliable 
basis for judgment. Furthermore, the fish have been taken from the ponds during 
every month in the year except December, January, and February, and thus include 
as much of the yearly life cycle as is available. 
Very small fish do not eat odonate nymphs. Of the largemouth black bass from 
pond 3 only one, and that the largest of them all, had taken a damselfly nymph; eight 
specimens of bluegills, averaging less than 10 mm. in length, from ponds 1 and 2, did 
not show any trace of odonate food; and the five channel cats that averaged only 9 mm. 
in length from pond 9 had eaten nothing as large as an odonate nymph. 
While these small fish refuse the nymphs, they do not refuse the eggs which the 
dragonflies distribute so freely about the ponds. Of the 22 buffalofish from pond 7D 
only 1 had eaten dragonfly eggs. But among 59 sunfish from pond 15B, 10 were found 
to have eaten dragonfly eggs; these 10 fish averaged but 13 mm. in length, the shortest 
being 10 mm. long and the longest 18 mm. Odonate eggs formed 55 per cent (average) 
of the food of these ro fish and reached as high as 98 per cent in one of them. Hence 
for some kinds of fish odonate eggs will furnish an acceptable food, while the young 
fry are from 10 to 20 mm. in length. 
Judging from the records of the largemouth bass, the bluegill, the common sunfish, 
and the calico bass, young fish must attain a length of from 22 to 25 mm. before they 
begin to eat odonate nymphs. From 25 to 40 mm. they take them in comparatively 
small numbers; from 40 to 100 mm. they eat them in much larger quantities, and 
often eat nothing else. In every instance where the odonate food constituted 100 
per cent the fish was over 40 mm. in length and nine-tenths of them were over 50 mm. 
From 50 to 80 mm., therefore, may be taken as the size of fish for which odonate nymphs 
will prove most serviceable as food. 
The stomach contents of a largemouth black bass, 80 mm. long, examined July 
30, 1917, consisted of three fully grown nymphs of L. luctuosa, one fully grown nymph of 
Erythemis, and the remainder of the food fragments of similar nymphs too far digested 
for identification. 
The small percentage of odonate food in the stomachs of the common sunfish 
and the calico bass may well be due to the small size of the fish examined. Of the 173 
common sunfish included in the table, 96 were under 25 mm. in length and only 32 were 
30 mm. or over in length, so that really the 1o fish which ate odonate nymphs were 
10 out of 32 rather than 10 out of 173. Similarly, among the 143 calico bass there were 
only 21 that reached 35 mm. in length, while 100 were between 26 and 34 mm., just the 
size when they begin to eat sparingly of nymphs. The calico bass does not seem to 
begin this diet quite as early in life as some of the other fish, although the table of the 
Madison fish shows that the adults eat damselfly nymphs in goodly numbers. If we 
remove from the lists here given all the fish 25 mm. in length or under—namely, those 
that were too small to be expected to eat odonate food—it can readily be seen that the 
percentage of odonate feeders would be considerably increased. 
We may next consider the fish’s diet from a seasonal standpoint—the examination 
of fish food began in the latter part of June and continued through the summer and 
fall. Both the fish and the nymphs were steadily increasing in size during the period. 
