64 
(T. inornata earlier), feed on the flowers of such weeds as asters and 
parsnips or the honeydew of plant-lice (especially that of Aphis maidis 
Fitch), mate, and re-enter the ground to parasitize the common white- 
grub. The grub is first paralyzed, the wasp stinging it on the under 
side of the first or second thoracic segment, and an egg is then laid on 
the dorsum of the thorax, the under side of the abdomen, or elsewhere, 
according to the species of Tiphia. The egg is firmly attached to the 
body of the grub by a glutinous secretion which is at first colorless but 
later darkens to brown. In the process of oviposition the wasp, after 
paralyzing the grub, encircles the body so that the tip of its abdomen 
touches that point on the body of the host to which the egg is to be 
attached. The wasp then moves the tip of its abdomen back and forth 
in a fold or crevice of the skin for several minutes, all the while spread- 
ing the secretion which serves to attach the egg securely to the body of 
the grub. Under natural conditions the Tiphia attacks the grub in its 
earthen cell, but when a grub is exposed on the surface of the soil, the 
wasp stings it and then proceeds to undermine and gradually to bury 
Fic. 6. Tiphia larva eating re- 
mains of grub after having 
killed it. 
the grub before laying an egg on it. The egg having been laid the grub 
gradually returns to normal activity, the paralysis brought on by the 
sting of the wasp lasting only about an hour, or even less, and serving 
only to quiet the grub during the act of oviposition. Ordinarily but one 
egg is laid on a single grub, although in our cage experiments the wasp 
would in exceptional cases lay two or even three eggs on a single grub. 
That a second egg may be laid on a grub in the field if the first egg was 
dislodged is shown by the old egg-scars on grubs bearing an egg or larva, 
but we never have found a grub in the field which bore more than one 
egg or larva. Not infrequently the grub may molt soon after being 
parasitized, thus throwing off the egg or young larva, and once dislodged 
the parasite dies since it can not regain its position on the host. The egg 
hatches in four or five days, but in the beginning only the head pro- 
trudes. The larva immediately pierces the integument with its mandibles 
and begins to suck the body fluids, the grub apparently being unaware 
of its enemy. Within 5 or 6 hours the growth of the larva is sufficient 
to start an irregular longitudinal splitting of the egg-shell, and in 12 to 
