320 Dr. T. A. Chapman on the Life-History 
segments, the ventral ones about the middle of each segment. 
All these plates are of a delicately tessellated structure, as if 
constructed of flattened cells arranged in arches springing 
om their posterior margins ; the femora have a similar struc- 
ture, and, in a prepared specimen, I see that their dorsal 
margin is toothed where the different cells overlap eac 
other, 
These plates may be regarded as a beautiful display of the 
dermal anatomy of the little active larva; and the above de- 
scription is doubtless equally applicable to it. As a parallel 
instance I may refer to the case of the female of the white 
ant, as described by Smeathman, where he mentions the 
Pulex penetrans as the only similar instance known to him. 
In examining the little active larva I did not notice any sete, 
except a short one at the side of each segment; these were 
probably those of the secondary dorsal plates. I found more 
an a dozen of these larve within full-grown wasp-larve, 
and had the pleasure of watching three of them emerge from 
the wasp-grub. The usual, and, I believe, the only normal, 
place to emerge is at the anterior aspect of the fourth segment 
(head = 1st). The Rhipiphorus, which is usually in motion, 
and for its situation might be called tolerably active, is seen 
to Y hold of the interior of the skin with its anterior legs, 
and eeps biting and scratching with its strong and sharp jaws 
until itis able to thrust through its head, when, in less than 
a quarter of an hour, it completely emerges by a vermi orm 
movement ; and at the same time it casts a skin, together with 
the black head,legs,plates,&e. Its anterior surface as it emerges 
is directed towards the head of the wasp, and, bending for- 
wards as it emerges, and guided probably when in its natural 
position by the wall of the cell, it passes forwards as it emerges 
along the anterior surface of the wasp-grub, until its head 
comes somewhere near the second segment of the wasp on Its 
dorsal or lateral aspect, where it at once seizes hold. When 
removed from the cell, as those I examined were, the first few 
segments of the Rhipiphorus came directly outwards, though 
they equally succeeded in seizing the wasp-grub by the shoul- 
der. The place of emergence is marked by a slight puckering, 
and by the black particles of the cast skin. There seems to be 
no escape of fluid from the wound thus made: for one thing, 
it 15 smaller than the diameter of the Rhipiphorus-larva, which 
squeezes through it and plugs it for the time; and afterwards 1t 
1s to a certain extent stopped by the cast skin of the Rhdpt- 
phorus. 
The position of the Rhipiphorus-larva inside that of the 
wasp, when it is ready to emerge, is with the head to the 
