220 MODERN CLASSIFICATION OF INSECTS, 
and Typhlopone fulva W., they are only 2-jointed (fig. 86. 20.). 
The thorax is very variable in its shape, especially in the neuters ; its 
composition differs also according to the presence or absence of 
wings; in the winged individuals the collar is large (fig. 85.* 10. 9, 
h the head, t 1 collar), the mesothoracic scutum (t 2) and its scu- 
tellum (t 3) distinct from each other; the metathoracic prascutum 
(t 4) and its scutellum (e) also distinct, the collar and the metathorax 
exhibiting a spiracle on each side. In the neuters, however (fig. 85. 
17.), the composition of the thorax is quite simple, consisting of the 
three segments quite distinct from each other, and each provided with 
a spiracle on each side. 
The abdomen of the males is composed of seven segments, but 
in the females and neuters of only six; the first, and in some genera 
also the second (as in fig. 86. 16.), forms a lenticular scale or knot, 
varying in form, and serving as a peduncle to the abdomen. Some of 
these species, especially those which have only a single scale, are 
destitute of a sting+, and in such case the abdomen is larger in the 
females than in those species which are armed with that instrument, 
which exists invariably in those species which have the peduncle 
formed of two knots. ‘The males of the former species have the ab- 
domen more trigonate, whilst in the latter it scarcely differs in form 
from that of the females. The external sexual organs of the males of 
Formica fusca are represented in fig. 85.5. The wings are of large 
size, and of a delicate texture; they exist only in the males and fe- 
males; they are furnished with much fewer cells than in the wasps, 
&c., and the veins of the wings are often irregular: thus, in the wing 
of Myrmica (fig. 86.10.), a vein will be perceived to terminate abruptly 
in the middle of the first submarginal cell. The legs are of moderate 
or considerable length; they are generally simple, unfurnished with 
fossorial cilia, with the tarsi 5-jointed. 
* In figures 85. 10. & 17. the prothorax and metathorax are dotted, to distinguish 
them from the mesothorax. A comparative examination of these two figures with 
those given in previous pages of the composition of the thorax of other Hymeno- 
ptera will, I think, most satisfactorily prove that the hind part of the thorax is not, 
as asserted by Audouin and Latreille, the anterior segments of the abdomen soldered 
to the real thorax. 
++ Those species which are destitute of a sting are provided with glands placed 
near the anus, which secrete and discharge a peculiar fluid, which has been termed 
formic acid, the composition of which, according to Berzelius, is as follows ; — 
hydrogen, 2°84; carbon, 32:40; oxygen, 64°76 = 100. 
See also Blot, in Mém. Soc. Linn. Calvados, vol. 1. ; and Zool. Journ. No. 4. 
