HOWE: NEW ENGLAND ODONATA 117 
well, while one has been taken as far south as New Jersey. In this 
case, contrary to the usual evidence, the migration was of northern 
species southward, rather than of southern species northward. 
Though fifty years as a unit of time in geologic history is infini- 
tesimal, yet there seems to be evidence accumulating to prove that 
species are extending their ranges westward, e.g., Enallagma ebrium 
(see Hagen and Elrod, Bull. No. 10, Univ. Mont., 151, 1902), and 
others eastward, e.g., Sympetrum corruptum (see Calvert, Trans. 
Amer. Ent. Soc.,Phila.,264, 269, 1893), and that Lower Austral spe- 
cies are pushing slowly northward along the Atlantic coastal strip, 
e.g.jPrionidus cristatus and Murgantia histrionica (Heteroptera) (see 
Kennedy, Ent. News, 31 : 208, 1920). There are several instances 
among the birds where perfectly definite changes and extensions of 
range have been recorded since the study of ornithology began in 
the United States. Besides these instances and though little defi- 
nite evidence is available there seem also to be indications that 
the east and west belt of so-called Transition and even Upper 
Austral species that were Boreal, and which were pushed south- 
ward by the ice advance, are now regaining lost territory, and are 
withdrawing their southern outposts (see Scudder, Amer. Journ. 
Sci., ser. 3, 48 : 178-187, 1894). Not only is this suggested by the 
failure in recent years to reestablish records of certain northern 
species made fifty years ago in the southern States, and of recent 
recording of "farthest north" records for the same and other 
species, e.g., Nehalennia irene, but, as has been said, by the season 
(early spring) and duration (brief) of the imaginal-lifo period of 
these species, and of their probable holarctic origin. 
Northern or Boreal Species 
The boreal species common to New England, of which thirty- 
two are transcontinental, number ninety-one. The Odonata as an 
order inhal)it largely the Austral and Tropical regions, and are 
represented less commonly in the Boreal. On the other hand, if we 
consider the so-called Transition Zone as belonging more naturally 
to the Boreal than to the Austral, these States should \)v occupied 
by a large proportion of northern species, particularly in view of 
the fact that their southern borders are still occupied by species the 
presence of which is explained by a former land connection with 
Newfoundland. The following sixteen species arc the most typi- 
