AQUATIC INSECTS 



891 



There is much diversity of egg-laying habits in the order. All 

 the damselflies and many dragonflies, especially Aeschnidae, are 

 provided with an ovipositor, by means of which punctures are 

 made in the stems of aquatic plants, in logs, in wet mud, etc., for 

 the reception of the eggs. The eggs are placed singly in the punc- 

 tures, and usually just below the surface of the water; but a few 

 damselflies descend the stems to place them deeper, and some 

 species of testes place them habitually in the stems above the sur- 

 face. Here they are subject to the attack of egg parasites. The 

 females of those dragonflies that lack a well-developed ovipositor 

 drop their eggs upon the surface of the water while in flight (usually 

 descending to touch the surface, and thus to wash them free), 

 whereupon the eggs scatter and fall to the bottom; or, they settle 

 on some plant stem at the surface and hang them in gelatinous 

 masses about the stem. In certain of the Cordulinae these masses 

 are long gelatinous strings, containing many hundreds of eggs. It 

 is easy to get the eggs of most Libellulines for study. When a fe- 

 male is seen tipping the surface of the water with her abdomen 

 while in flight, if she be captured uninjured and held by the tips 

 of the fore wings (leaving the hind wings free) and dipped against 

 the surface of the water in a glass, in imitation of her own motion 

 while at large, she wifl usually liberate eggs in great abundance in 

 the water. These require about three weeks for hatching, and the 

 nymphs begin to eat each other early in life. 



There are nymphs of Odonata in all sorts of fresh water. Those 

 of some of the larger active species clamber about freely among 



Fig. 1361. Damselfly nymphs; a, Calopteryx; b, Lestes. 



water weeds, and even chase their prey, creeping stealthily upon it 

 until within range. Most damselflies (Fig. 1361) clamber about 



