5 
phide, nearly all burrow in mud and sand. The imagos are 
usually of medium size, barred with green or yellow, the 
apical part of the abdomen often expanded to a greater or less 
extent. They are usually seen near water, but are not numer- 
ous as arule. The ovipositor is rudimentary or wanting and 
oviposition is exophytic, as in the remaining families. The 
eyes are small and widely separated, in which respect the fam- 
ily approaches the Zygoptera. The nymphs of the schnide 
and Gomphide differ but slightly in the structure of the labium 
and gizzard, and both these organs are quite similar to the 
type found in the Zygoptera. The next family, Cordulegaster- 
idw, is of special interest. It has but few species, and examples 
are rarely seen in Illinois. While evidently related to the pre- 
ceding families in different ways, the nymphs are like those of 
the Libellulide in having a spoon-shaped labium and a sym- 
metrically 4-toothed larval gizzard. The last family, Libe/lu- 
lide, comprises most of the commoner species. They are 
diversified in structure and habits, and may be grouped in three 
subfamiles. The first two of these (Synthemiinw and Cordu- 
liinw) have a number of common features and have hitherto 
been classed as one, but the wing structure and nymphal 
characters of the Synthemiine, represented in Illinois by Ma- 
cromia and Didymops, seem to warrant its separation from the 
Corduliine. The greater part of the family belongs to the L/- 
belludine, which includes three general types, exemplified by 
Sympetrum (Diplax), Libellula, and Tramea. The grouping of 
these is based by Mr. Adams on the extent of development of 
the ovipositor. 
LITERATURE. 
A list of the more important papers, to which references 
are made, is appended to this paper. A brief summary of their 
contents may be given here. 
On the nymphs, the most important papers are by Hagen 
and Cabot, describing and figuring the nymphs of the Museum 
of Comparative Zoology, at Cambridge. Cabot’s first paper (’72 
