( 22 ) 
for a more extensive generalization. The question of pa- 
rasites, to which I have referred above in my notice of the 
legs of these insects, is one deserving attention, and I 
would therefore suggest to collectors the propriety of re- 
cording every fact which opportunity may throw in the 
way of their observation. With respect to the apparent 
anomaly of parasites being of the same order, or perhaps 
of the same genus, it may be remarked that these are not 
internal parasites, and that perhaps a greater resemblance 
was necessary between the individuals than in the case of 
internal parasites, which I believe are destroyers of eggs 
and larvz exclusively, or at least they are deposited within 
the insect in those stages of its existence, and consequently 
when in an indefensive state. But here, where the food 
only, which is stored up as provision for the young, is the 
object of attack, and the maternal solicitude of the parent 
insect for the nurture of her offspring is rendered fruitless 
by the presence of an interpolater secretly deposited, it re- 
quired all the sagacity of the insect introducing her intru- 
sive progeny to evade the instinctive apprehension of the 
laborious mother, and nature has furnished additional 
means to foil the latter in the parasite’s resemblance to her- 
self. This appears plausible, but it is not yet substan- 
tiated, nor is it general; for we frequently observe a vast 
discrepancy between the two, although of the same order, 
for instance, between Odynerus and its parasite Chrysis, 
and between Osmia and its supposed parasite Sapyga punc- 
tata. Several Diptera are also found parasitic upon this 
tribe. The non-parasites among them provide their young 
with insects of several orders, and with Arachnides, but it 
is the Diptera chiefly upon which they prey, and I know 
but one instance in which a Coleopterous insect is subject 
to their attack, viz. Cerceris arenaria upon a Stropho- 
somus. 
