» 128 NATURAL HISTORY OF WASPS. 
from the anterior edge of each scale at either end. 
If all the muscles act together the whole abdomen is 
contracted. If only a portion of them act, on the 
ventral or dorsal surface, or on either side, for instance, 
that side is contracted, but the opposite side is 
lengthened. With the power of admitting and exclud- 
ing air at will, and thus of changing the fulcrum on 
which they act, this simple arrangement of the 
muscles is quite sufficient for all the requisite move- 
ments of the abdominal walls, which may be drawn 
out to their full length by alternate contractions of 
the opposite sides, or turned in any direction. 
The little slips of muscle may be traced without 
difficulty from the black dots which mark the points of 
their insertion into the abdominal scales. If we wish to 
carry our researches into this matter further, we must 
examine other insects and at a different period of their 
existence, and we shall do well to avail ourselves of 
the labours of other anatomists. 
For we shall gain a much more adequate idea 
of the elaborate nature of the muscular system of 
insects from a plate of the muscles of the cockchafer 
or of the privet-moth caterpillar* than from anything 
we may make out for ourselves, even in the largest 
hornet. Unless we devote a very large amount of 
labour, at a great expense of eyesight, to the subject. 
And the subject is scarcely worth it, for the arrange- 
ment of the muscles presents infinite varieties in 
different orders of insects, and in the same insect at 
different stages of its existence.t The muscles, like, 
* ‘Cyclopedia of Anatomy and Physiology,’ Insecta, Vol. II, 
pp. 937, 940. 
+ Van der Hoeven, ‘ Handbook of Zoology.’ Trans. Vol. I, p. 284. 
