54° 
Saw-flies, Gall-flies, Ichneumons, 
such a division of the group can be fairly made. These three families can 
be distinguished by the following key: 
Basal peduncle of the abdomen composed of a single segment (the first) (Fig. 743). 
Abdomen not constricted between the second and third segments (Fig. 743, r ). 
Camponotid^e. 
Abdomen constricted between the second and third segments (Fig. 743, 2 ) . Poneridse. 
Basal peduncle of the abdomen composed of two segments (Fig. 743, 3 ) . . Myrmicid^e. 
Of these families that of the Poneridae is the smallest in number of species, 
and includes the least specialized (as regards sharply marked division of 
labor, differentiation into castes, and complexity of 
the communal life) of all the ants. In the following 
brief accounts of a few of the better known American 
ants the family relationship of each of the species 
referred to is indicated. 
b 
Of the Poneridae only about 25 species are so far 
known in this country; all are stingers, although 
not very strong ones, and but a few species are at 
all common. Little was known of their habits 
Fig. 743.—Diagrams of 
lateral aspect of abdo¬ 
men of representatives 
of the three families of 
ants: 1, Camponotidse; 
2, Poneridse; 3, Myrmi- 
cidae. a, thorax; b, first 
abdominal segment; c, 
second abdominal seg¬ 
ment; d, third abdom¬ 
inal segment. 
and life-history before the recent studies of Profes¬ 
sor Wheeler on three species occurring in Texas, 
namely, Odontomachus hcematodes , Pachycondyla 
harpax , and Leptogenys elongata. The nests, made 
under stones or logs, are primitive structures, com¬ 
posed of a few simple and irregular burrows or gal¬ 
leries, some of which run along the surface of the 
soil immediately beneath the stone or log, while 
others extend obliquely or vertically downwards 
for from 8 to 10 inches. There are no widened 
chambers. The nests of L. elongata comprise ten 
to fifty individuals, those of P. harpax fifteen to one hundred, and those of 
O. hcematodes one hundred to two hundred. Ergatoid (worker-like) females, 
no larger than and almost exactly like the true workers, existed in all the 
nests; the workers of none of the species fed each other or the males and 
females, and the larvae were fed simply by giving them pieces of freshly killed 
insects, which they chewed and devoured by means of their unusually well- 
developed mandibles. This method of larval feeding is more primitive 
(demands less care and manipulation on the part of the workers) than in 
the case of any other ants,—indeed of any other social insects, for even the 
wasps, which also feed their young pieces of insects, masticate these insect 
morsels thoroughly before turning them over to the tender larvae. The 
feeding of the Ponerine larvae is also very irregular and capricious both as 
