HOWE: NEW ENGLAND ODONATA 111 
and of Tramea Carolina north of its normal range, all three fljdng 
together over a small bog pond where they breed and transform, 
needed investigation. The taking of a series of water tempera- 
tures from the bottom of this bog pond, and a comparison of those 
temperatures with others taken in a glacial pond in the same town- 
ship (Lat. 42° 25', elevation 200 ft.) has given some interesting data. 
The cold springs that evidently feed this bog pond keep the bot- 
tom temperature at 51° F. in summer, while in winter the pond 
hardly freezes over, and its bottom temperature falls only to 
36° F., or a range of 15° F. At the other pond the winter and 
summer bottom temperatures ranged through 33° F., or from 3b° 
to 69° F. It would seem therefore quite natural that the larvae 
of the Lencorrhinias would find a summer temperature not too 
warm, — and those of Tramea Carolina, a winter one not too low. 
As both imagoes enjoy warm sunlight their imaginal lives are also 
satisfied. 
Migration 
The migration of insects is an established fact, and that of the 
Odonata has been frequently observed and recorded. Whether 
or not it is a relic of glacial invasion and retreat, and follows an- 
cestral routes, as does that of birds, is unknown. A swarming, 
similar to that of swallows preceding the migration movement, has 
been noted by the author and others, and a definite southward 
trend of migration along the beaches of our coast is observable 
every autumn. Northward spring migrations have also been re- 
corded. The migrations are confined to the larger species of strong 
flight, and it would seem that distributional extension must at 
times result. Anax Junius, a regular migrant, is for example, the 
species of widest North American range, and LibeUula pulchella 
and L. semifasciata, Tramea Carolina and T. laccrata, and many 
Aeshna species which have been commonly recorded on migra- 
tions, have extensive ranges (Shannon, Harper's Month. IMag., 131: 
Sept., 609-618, 1915; Shannon, Sci. Monthly, 3 : 227-240, 1916; 
Osburn, Journ. N. Y. Ent. Soc, 24 : 90-92, 1916; Walker, Can. 
Ent., 17 : 172, 1917; Torrey, Amer. Nat., 14 : 132-133, 1880. and 
594, 1881). 
