Wasps, Bees, and Ants 
483 
attack on certain of the solid tissues, as muscles, fat-body, etc. Such attacks 
necessarily avoid the vital organs or the host would be killed long before 
the parasitic larva is ready to pupate. With regard to the breathing it has 
been variously suggested that the larva applies itself to air-tubes (tracheae) 
in the host-body in such a way as to effect an exchange of gases; that it needs 
no more oxygen than it obtains in the body fluid of the host; that its rela¬ 
tion to the host is analogous to that of foetus to mother among viviparous 
animals. Seurat’s observations seem to indicate (for certain species at 
least) that solid food as well as blood-lymph is taken in; that respiration 
is effected through the skin by osmosis, that excretion from the intestine 
does not occur until after the pupal cocoon is formed, and that moulting 
actually occurs. 
The host of species and the difficulties attending their determination, 
even (for amateurs) as regards their family classification, let alone their 
generic and specific identification, have led me to avoid any reference to the 
systematic study of these parasites. Certain particular species, especially 
among the larger forms, are of course more or less re¬ 
cognizable and familiar to observers. Among the larger 
species, most of which belong to the superfamily 
Ichneumonoidea, those of the genera Pimpla (Fig. 678) 
and Ophion (Fig. 679) are especially familiar. P. con- 
quisitor (Fig. 680) is the commonest parasite of the tent- 
caterpillars (Clisiocampa), is also the chief one of the de¬ 
structive cotton-worm, Aletia argillacea, of the south and 
has been bred from half a dozen other species of moths. 
It lays its eggs not on the larvae of the tent-caterpillar 
moth, but on the pupae (and perhaps on the cater¬ 
pillars after spinning and just before pupating) inside 
the silken cocoon (Fig. 680). P. inquisitor , a common 
parasite of the tussock-caterpillars, is an ichneumon- 
fly whose life-history is given in much detail by Howard 
in the Insect Book. The Ophions are light brown or 
golden in color, with abdomen much compressed laterally. A common 
species parasitizes the giant larvae of the polyphemus moth; but huge as 
this caterpillar is, only one egg is laid on it by the Ophion. 
The wonderful Thalessa, with its flexible ovipositor six inches long, with 
which it drills a hole deep into a tree-trunk until it reaches a tunnel of the 
wood-boring larva of Tremex, has already been referred to (see p. 467). 
Comstock describes Thalessa as follows: “Its body is 2\ inches long and it 
measures nearly 10 inches from tip of antenna to tip of the ovipositor. 
When a female finds a tree infested by the Tremex she selects a place which 
she judges is opposite a Tremex-buriow, and, elevating her long ovipositor 
Fig. 680. — Pimpla 
conquisitor, laying 
egg in cocoon of 
American tent-cater¬ 
pillar moth. (After 
Fiske; about natural 
size.) 
