12 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



require three or four years to develop. Zygoptera or damsel flies 

 begin to emerge early in spring (April), and some species continue 

 to emerge until fall (September). Some of the larger Anisoptera 

 are more frequently seen in July, August and September, their 

 emergence taking place during late summer, Cordulines and 

 Gomphines are most abundant in June. 



Most damsel fly nymphs may be taken among vegetation of one 

 sort or another, but a few occur under rocks or rotten logs in 

 swift currents. The Anisoptera may be found mostly in the mud 

 at the bottom of the stream or lake, where they conceal themselves 

 by attaching rubbish to their bodies, or by burrowing in the mud 

 itself. Some, of course, inhabit floating vegetation. 



Odonata are fond of unpolluted water and do not thrive where 

 there is much contamination. Ponds and lakes about which cows 

 or horses are allowed to graze are frequently without dragonflies, 

 or with only a few of the more hardy species. The gradual pollu- 

 tion of fresh water in the New England States and elsewhere has, 

 moreover, reduced the relative numbers of dragonflies so that one 

 should collect in many localities to obtain a complete collection 

 of these interesting creatures. Fortunately many lakes have 

 become public property and included in parks and estates, while 

 still others have become reservoirs for the supply of towns, cities 

 and villages, and the sources of contamination removed or abated. 

 For this reason the dragonfly's prospects for the future are better, 

 though evidently they are not as numerous as a half -century ago. 



Many families of dragonflies select their environment, and some 

 species may nearly always be found under certain ecological con- 

 ditions. For instance, the nymphs of the Agrionidae, among 

 which the black-wings are perhaps the most common examples, 

 are found in clear woodland or meadow brooks. The nymphs 

 of Argias are most frequently found in running or moving water 

 under stones, logs, etc., and the Lestinae, most frequently in bogs 

 or fresh water ponds with considerable vegetation. Among the 

 Anisoptera selection of environment is not as evident, but we find 

 many Gomphidae in shallow, slow-flowing streams ; a species of 

 Libellulid (Erythrodiplax Berenice) confined to brackish water 

 along the sea coast ; Sympetrum species frequenting bogs and 

 marshes, and so on. Adults of certain species may be found 

 fairly close to their nymphal environment, but some wander long 

 distances from their former aquatic home. Aeshna species may 

 be seen frequently a mile or so from the nearest water, and it seems 

 likely that they fly many times this distance away from their 

 natural haunts. Other species are known to congregate in sunny 

 spots away from the water on the approach of cold weather. Still 

 others prefer pasture lands as a hunting ground or the clear 

 expanse of a lake or pond. The congregation of species may 

 perhaps be connected with the migration of such as Anax Junius, 



