NATURAL ENEMIES OF THE LOCUST. 
261 
exceptional individuals as should not develop till two, three, or more 
years after a locust invasion might stand a much better chance of find- 
ing appropriate food and of thus perpetuating the species. In this case 
and in most other cases of retarded development with which we are 
familiar, the exceptional retardation may and does become a benefit to 
the species, enabling it to bridge over periods of adversity. And we 
can see how, by the preservation of such favored individuals, the habit 
of irregular development may have become fixed in the species as a con- 
sequence of surrounding conditions and circumstances which render it 
advantageous. 
Soldier-beetle larvae. — We are not aware that the early larval 
characters of these beetles have ever, before been observed. Since our 
First Eeport was written we have obtained the eggs of the Pennsylvania 
Soldier-beetle (Chauliognathus pennsylvanicus, De Geer) and hatched the 
young larvae and fed them until they were nearly full grown. The eggs 
are deposited loosely in the ground in irregular batches very much in the 
same way as those of the blister-beetles, but are readily distinguished 
from these last by being almost spherical or but very slightly longer than 
wide. They are pure white and opaque, the shell being tolerably firm 
and having no sculpture. Mr. H. G. Hubbard, whom we charged with 
rearing the larvae, found that they feu on a number of insects, but showed 
a great preference for those, like fly maggots for instance, which have a 
soft integument. They molt quite frequently, huddling together during 
the process, which would indicate that in their earlier stages at least 
they are more or less gregarious. We quote Mr. Hubbard's notes : 
The eggs of Chauliognathus pennsylvanicus, which you gave rue at Savannah, hatched 
during the night of August 9. The young larva} were silver-gray in color. They 
■were very timid, hut sucked up the juices of plant-lice, the bodies of which were 
crushed for them against the sides of the breeding-jar. August 12 the larva} retreated 
to the bottom of the earth in the bottle, aud curled up in clusters. In two or three 
hours they had moulted, and immediately became very active, climbing all over the 
sides of the jar. The anal prop-leg acts as a sucker, aud enables them to adhere to 
the glass in any position while sweeping the body around in every direction in search 
of food. I gave them crushed maggots of Phora aletiw, and they sucked the juices 
greedily. They became bolder, and attacked the uninjured maggots, but were unable 
to pierce the skin. August 15 I gave them a species of large red Aphis found on cockle- 
bur, but they did not relish them, and ate but little. They also ate sparingly of 
crushed Aletia larvra, but preferred the Phoras to everything else. August 17 they 
retired to the bottom of the jar, and remained torpid two days. August 19 all had 
completed their second moult. They were now quite bold and strong, and able to 
pierce the skin of Phora maggots given them for food. In feeding, the maggot is 
punctured by the sharp tips of the jaws, which are then used as hooks to draw in a 
fold of the skin ; this is held between the molar lobes at the base of the mandibles, and 
the juices are sucked by the pumping action of the oesophagus, which is thrown into 
peristaltic waves. The large mentum is very elastic and mobile, and evidently per- 
forms the usual office of a lower lip. An occasional quick movement of the jaws is 
made, either to give a squeeze with the molar surfaces, or to take a better hold with 
the hooked tips. 
The basal joint of the antenna is very elastic, and enables the larva to elongate 
