70 The American Naturalist. [January,. 
destroyed until they have reached their full growth and have done all 
the damage to the farmer that they could have done had they not been 
parasitized at all. In other words, the fact that fifty per cent of the- 
cutworms in his field are infested by parasites does not help the far- 
mer in the least.” But obviously it does help the farmer very greatly 
the neat season, for it reduces by half the number of cutworms he will have- 
to contend with. As a matter of fact cutworms fluctuate in numbers 
in a way quite similar to the army worm, and the fluctuations are largely 
due to parasitic enemies. I have seen regions where cutworms were so 
abundant that grain fields were literally cut off by them as by a mow- 
ing machine, and the following season the worms were so scarce as to 
do practically no damage. Even the plum curculio and the Colorado 
potato bettle are sometimes so scarce as to require no protection against 
them, and presumption is in favor of parasites as a cause of their 
scarcity. 
But Professor Smith is right in saying that as a general rule there is- 
too great a tendency to rely on natural enemies to subdue insect 
attack. Itis nearly always safer to adopt effective measures in keep- 
ing pests in check than to trust to the chanceof their natural enemies- 
subduing them. As Dr. C. V. Riley has pointed out, “there are but 
two methods by which these insect friends of the farmer can be effect- 
ually utilized or encouraged, as for the most part they perform their 
work unseen and unheeded by him, and are practically beyond his- 
control. These methods consist in the intelligent protection of those 
species which already exist in a given Tocality and in the introduction 
of desirable species which do not already exist there.” 
CLARENCE M. WEED. 
Oviposition in Acridiidæ.—M. J. Kiinckel d’ Herculais describes? 
the means by which these Orthoptera bury their abdomen in the 
ground ; there is no perforation of the ground, the hinder part of the 
body is merely forced into it; as the Arabs say the female “ plantent.” 
On dissecting females whose abdomen had reached the maximum of 
distension, the author was surprised to find that the abdomen was 
filled with air; on the air being withdrawn, the abdomen was reduced 
from 8 to 5 cm, in length. When the position is firmly taken up the 
females of the migratory locust maintain the parts of their genital 
armor as widely separated as possible, and secrete a viscous material 
which agglutinates the grains of sand, or the particles of earth at the 
bottom of the cavity, and they then begin to lay their eggs. These 
