$96 MODERN CLASSIFICATION OF INSECTS. 

3. Abraxas grossulariata). The head is of moderate size; the maxille 
short and weak, being nearly membranous ; the labial palpi small and 
cylindrical ; the antennz variable, being strongly bipectinated in 
some males (jig. 109. 6. antenna of Himera pennaria g; 4. head of 
Ourapteryx sambucaria g; 5. part of its antenna; 7. joint of an- 
tenna of Hybernia defoliaria ¢ ). The wings are of large size, and 
various outlines, and are often extended horizontally (in a few species 
they are occasionally carried vertically ). The thorax is never crested. 
The legs are slender, the anterior tibia being armed internally with a 
spur (fig. 109. 8.), and the posterior with two pairs of those appen- 
dages. 
The caterpillars are called loopers, or geometricians, from the 
peculiar mode of their progression. They have only three pairs of 
pectoral, and one (the hindmost) pair of ventral prolegs, with a pair 
of anal feet; and hence, in walking, they first fix themselves firmly, 
by means of their anal and ventral feet ; they then extend the body 
to its greatest length, when they put down their fore feet, drawing 
the hind part of the body as close after them as possible, so as to 
form an arch, like a pair of compasses, fixing their hind feet, and 
proceeding again as before. Their muscular power is very great, 
and hence their positions during repose are very striking. Fixing 
themselves by their anal feet alone, they extend their bodies in a 
straight line, holding it in that position for a great length of time. 
This, together with their obscure colours, and the warts which 
their body exhibits, renders it often quite difficult to distinguish them 
from twigs of the trees on which they feed (fig. 109. 11. young larva 
of Ourapteryx sambucaria in its stationary attitude; 10. ditto just 
hatched, showing them in various positions ; 1. geometrical position 
