1908] 
Muttkoivski, Dragon Flies of Wisconsin. 
61 
attacking its own kind, when nothing else offers. The nymph 
eats insects, small fish, tadpoles and other aquatic animals. The 
food of the imago is formed chiefly of insects, such as mosquitoes, 
flies, and occasionally moths. Undoubtedly the economic value 
of the adult dragon-fly is great, since myriads of harmful insects 
are destroyed by them. The nymph, too, partakes of this attri- 
bute though its economic value is less certain. In fact, at times 
nymphs may become a regular plague by over-population, to 
the detriment of other aquatic animals. Instances are known 
where large fish-ponds were completely depopulated by voracious 
odonate nymphs that infested them. For voracity these nymphs 
easily take the crown among insects. 
COLLECTION AND PRESERVATION. In the capture 
of dragon-flies activity is the most necessary requirement. Their 
flight is usually so rapid that often they cannot be caught by pur- 
suit, but must be met with according to their own tactics. Wait- 
ing till the dragon-fly alights which it usually does near its origi- 
nal resting-place, a rapid swoop with the net from behind will 
prove efficient. A sweep with the water-net along the bottom of 
shallow ponds and rivers will land many nymphs. Later in the 
season the rank growth on the bottoms prohibits the use of a net, 
when a rake is advisable. 
For preservation the rapid drying process is the most adequate. 
A slit on each side of the thorax and in the venter of the basal 
abdominal segments, with exposure to the direct rays of the sun 
will complete drying within little more than an hour, and preserve 
the original colors. Thus prepared the insect should be placed in 
a dark cabinet. Alcohol is a commendable medium for the preser- 
vation of smaller species, since it retains the original coloration. 
This is w^ell for exhibition purposes, but for collection series it is 
impracticable. There the drying process is likewise the best, 
though fading of colors is unavoidable ; but since dragon-flies are 
usually common where they occur they are readily replaced. 
