72 NATURAL HISTORY OF WASPS. 
rest, in the Social, but hooked in the Solitary group, 
and furnishes a most useful aid in classification. The 
front of the scape is yellow, as already noticed, in 
all the sexes of the tree-wasps, and in the males of 
the ground-wasps. It is important to recollect this, 
as well as the number of the jomts, and the fact of 
the terminal jomt bemg hooked in the males of the 
Solitary group. 
A longitudinal section of the antenne of the 
hornet discloses a series of chambers jomted together. _ 
The central space, according to Mr. Newport's de- 
scription of the antenne of Jchnewmon Atropos, is 
occupied by a nervous filament, and copiously sup- 
plied with a limpid fluid. On either side of this, in 
the hornet, is a trachea, contracted at the jomts, but 
swelling out m the interspaces, and giving origin to 
little air tubes which ramify over the interior of the 
horny covering. This covering is composed of fibres, 
forcibly recallmg the appearance and arrangement of 
the enamel fibres of the teeth, radiating from the 
long axis of the antenna, presenting a rough surface 
externally. A longitudinal section of one of these. 
antenne, under polarized light, is an object of ex- 
ceeding beauty. 
Popularly the antennz are known as the insect’s 
feelers, and certainly one of their uses is to examine 
by touch anything presented to them. If we con- 
fine one of the Orthoptera, a cricket or grasshopper, 
for instance, with its fine, long, antennew, in a box 
with a glass lid, we may easily satisfy ourselves on 
this point. But they are not the only organs of 
touch, as the palpi of the mouth share this sense 
with them; nor are their functions limited to the 
