NOVEMBER, 1905. SOME OBSERVATIONS ON PARASITIC BEES. 
163 
out considerably at its anterior (cephalic) pole. On account of 
its peculiar shape the egg can not pass through the slit in its 
entirety. With its lower two-thirds it is resting between the 
inner and the adjoining layer of leaves while the upper portion 
protrudes slightly into the bee-bread. This mode of oviposition 
explains the purposes served by the characteristic structure of the 
conical sharp-pointed abdomen in Ccelioxys. 
In the nests discussed above either a single egg or a single . 
larva of the parasite Ccelioxys had been come across in the same 
cell, but at Cedar Lake on September 26, 1903 a nest of Megachile 
latimanus was found with 4 eggs of the parasite in one cell. They 
were not far apart from each other, but all of them were situated 
nearer to the bottom of the cell than to the surface of the bee- 
bread. 
The host-bee Megachile latimanus extends its nest-building 
activity into the first half of October and its parasite Ccelioxys 
rufttarsis is still in evidence at this time of the year. On October 
3, 1903, a female of this parasitic bee was captured at Milwaukee 
flying around an embankment in search of the nests of its host, 
and a dissection of this specimen brought 4 eggs to view, one of 
which was ready to leave the body, while the others were in dif- 
ferent stages of development. This bee, our largest species of 
Ccelioxys is, as fe have seen a parasite of two species of Megachile 
that build their nests in the ground. It produces at least two 
broods a year, the bees of the first appearing around the begin- 
ning of July from hybernated specimens (probably passing the 
winter as larvae), those of the second brood coming out about 2 
months later. Besides the specimen reared from the nest of 
Megachile melanophwa I obtained an additional one from a nest 
of M. latimanus opened at Milwaukee on July 20, 1904. The 
larva in this case spun its cocoon on July 23, pupated on August 
1, and emerged as a bee on August 20. 
While the larva of Stelis sexmaculata the parasite of 
Alcidamea pmducta is equipped with simple and sharp, but not 
large mandibles, the larva of Ccelioxys leaves the egg with mand- 
ibles of enormous dimensions. These are very effective as weap- 
ons of attack but rather inconvenient for their owner when the 
latter is engaged in taking up food. Several days after the larva 
has appeared on the surface of the bee-bread, a period sufficiently 
long for the parasite to perform its deadly work, mandibles and 
head-shield are thrown off by moulting, and replaced by a round 
head with short mandibles. Before the moulting process we have 
the head of a rapacious larva, afterwards one more adapted to 
