OCT. 1906. HABITS AND LIFE-HISTORY OF LEUCOSPIS AFFINIS SAY. 
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females of the first generation are derived from hibernating larvae 
that pupate in the spring, and these females lay their eggs at some 
time during the month of July. These eggs give rise to the second 
generation, the females of which appear in the month of August 
or perhaps a little later. They in turn produce the eggs for the 
following year. It is a noteworthy fact that not all of the 
descendants of the first generation reach the imago-stage 
during the same year as shown by finding on July 31st three 
full-grown larvae in a nest of Osmia pumila that passed the winter 
as larvae. 
The female of Leucospis is able to locate the cell of the bee 
with a considerable degree of certainty, but she is also liable to 
commit grave errors as has been pointed out by Fabre. This 
author observed Leucospis gigas ovipositing in old and empty cells, 
and he also calls attention to the fact that the insect is incapable 
of ascertaining whether a cell has already received an egg of its 
kind or not, and as a result several eggs may be dropped into the 
same cell. I have twice found in the nest of Osmia simillima an 
egg of Leucospis afhnis on a bee-larva that had been dead at the 
time the egg was deposited. This failure of the parasite to dis- 
tinguish between a dead and a living larva in a cell is certain to 
bring disaster to its offspring, since the latter can subsist on the 
contents of a living larva only. In the nest of Osmia atriventris 
opened on July 13th of the present year the parasite had laid an 
egg in a cell with a half-grown bee-larva. In such a case the larva 
of the parasite has a scanty food-supply, and it either perishes 
from lack of food, or else it developes into an undersized imago. 
Leucospis afhnis is extremely variable in size, the smallest specimen 
in my collection being only 6 mm. long, while the largest one shows 
a length of over 1 1 mm. The smallest one has probably come from 
such a poorly fed larva as referred to above, since a specimen 
bred from the nest of Osmia pumila, our smallest species of Osmia 
is decidedly larger, being 8 mm. in length. According to Guerin 
(cited by Dalle Torre in his Catalogus Hymenopterorum) this 
parasite preys also upon a Cuban species of leaf-cutter bee Meg- 
achile poeyi Guer. 
