1912] Ecology of Dragon-fly Nymphs Bik 
states that Ranatra, Notonecta, and Belostoma all prey upon 
the young nymphs of dragon-flies. From the context, one 
infers that Aaron’s statement is based upon out-of-door obser- 
vations. 
Incidental observations were made upon the enemies of the 
dragon-fly nymphs when kept in confinement. In one aquar- 
ium, there were a number of the Agrionid nymphs and three 
Belostomas. In another aquarium, there were several of the 
nymphs and one Ranatra. It was found that both of these 
aquatic bugs preyed on the dragon-fly nymphs. At least 
three definite records were obtained with reference to Belos- 
toma and two with reference to Ranatra. The nymph is seized 
by means of the first pair of legs—in the case of both Belos- 
toma and Ranatra—and after the bug has placed its prey in a 
convenient positon, the “bill-like’’ mouth parts are pushed 
into the softer portions of the body, and the juices sucked out. 
Bueno (1908, p. 285) gives a good description of the method 
used by Ranatra in catching its prey. The behavior of Belos- 
toma, when engaged in obtaining food is interestingly described 
by Severin and Severin (1911, pp. 101-102). Other naturalists 
have observed that many insects are enemies of dragon-fly 
nymphs while in confinement. Severin and Severin (1911, 
pp. 102-104) state that Belostoma and Nepa are both enemies 
of dragon-fly nymphs and prey upon them. Weed (1889, pp. 
11-12) has noticed that in his aquaria the most important 
element of food of Belostoma, consisted of the nymphs of the 
larger dragon-flies. 
FOOD. 
The Agrionid nymphs are largely predaceous in their manner 
of feeding. They feed upon small Crustaceans and the nymphs 
of certain other small forms, particularly upon the nymphs of 
May-flies. It is a task of considerable difficulty and one 
requiring much patience to observe these organisms feeding in 
their natural habitat. The writer has observed, that in cap- 
tivity, they feed upon each other, especially is this true, when 
the food supply is not abundant. Three dozen specimens were 
placed in an aquarium jar, no food being added, and at the end 
of three months there were two.nymphs alive in the jar. One 
can readily see the nymph in the very act of seizing its food, in 
an aquarium jar. The prey is seized by the lobes of the labium, 
this organ being thrust forward with great rapidity. The 
