1912] Ecology of Dragon-fly Nymphs 205 
goniotaxis to such responses. In an interesting paper on the 
death-feigning of Belostoma, Severin and Severin (1911la, p. 38) 
have described how this insect also reacts to the contact of 
aquatic vegetation. 
The dragon-fly nymphs lie in wait for their prey on these 
aquatic plants. They are effectually concealed in such posi- 
tions. The diameter of their bodies is about that of the thicker 
stems, and the creatures he so quietly that they are easily over- 
looked. Then also their colors are much like those of the vege- 
tation—browns and greens predominating. Facts of somewhat 
similar nature have been recorded by Holmes (1905, pp. 308-809) 
in his observations on Ranatra. In collecting the dragon-fly 
nymphs, the writer often rakes some of the plant material out 
of the water. The animals are then picked from the Elodea and 
Ceratophyllum. It is not at all an uncommon thing for many of 
them to be overlooked; because after the plants have been taken 
to the laboratory and placed in an aquarium jar containing 
water, the nymphs can be seen swimming about freely or resting 
on the bottom. Having been disturbed in transit, they fre- 
quently leave their positions on the aquatic vegetation. The 
reason that some of them are so easily overlooked is due to 
three facts. First, they remain very quietly in their positions 
—though some of them are seen crawling over the vegetation 
after it has been shaken from the net; second, their shape and 
color resembles that of the plants on which they live; and third, 
they frequently feign death. The writer believes that the 
instinct of death-feigning is of much importance in the ecology 
of the animal. Itisaform of response which is certainly often 
highly protective. Many workers have frequently observed 
the death-feigning reaction among insects and to some extent 
the rdle which it plays in their lives. Among these observers 
may be mentioned the names of DeGeer, Fabre, Darwin 
(1884), Romanes (1884), and Whitman (1899). More recently 
papers by Holmes (1906) and Severin and Severin (1911la) have 
been written. Both of these deal with the death-feigning 
responses from a careful experimental point of view and are 
extremely valuable pieces of research. That the larve, nymphs, 
and imagoes of many aquatic insects evidence this interesting 
form of behavior is well brought out by these workers. This 
is especially the case in the paper by Severin and Severin 
(191 1a, p. 36). 
