296 
STRANGE DWELLINGS . 
and is evidently the produce of some lepidopterous insect, pro- 
bably a moth allied to the silkworm. Upon the larva which 
constructed the cocoon an ichneumon has laid her eggs, and 
the consequence has been that the caterpillar has been unable 
to change into the pupal condition, but has succumbed to the 
parasites which infested it. These insects are not of minute 
dimensions, like the Microgaster, but are tolerably large, and 
in consequence can be but few in number. The cells are very 
irregular in shape, and are not rounded like those of many 
Ichneumonidae, but have angular edges. 
Within the same case there are several cocoons in which a 
similar calamity has befallen the caterpillars which made them. |i 
There is, for example, a cocoon of the Oak-Egger Moth ( Lasio - |j 
campa quercus ), the interior of which resembles that of the insect ( 
which has just been described, except that the cells of the parasite 
are more numerous. This species of caterpillar is peculiarly 
subject to the attacks of the ichneumon flies, as is well known 
to all practical entomologists, who lose many of their carefully 
bred specimens by means of these insects. 
There is also one of the winter cocoons of the Goat Moth 
caterpillar, the inmate of which has been pierced by the ichneu- 
mon fly, and killed by its young. As the species of ichneumon 
is a large one, only a single individual was produced, and as may 
be seen from the cell of the parasite which is placed by the side 
of its victim, the habitation of the ichneumon is so large that it 
must have occupied nearly the entire cocoon of the dead cater- 
pillar. 
Those splendid insects which are popularly called Ruby- 
tailed Flies, or Firetails, and scientifically are termed 
Chrysididce , are also to be numbered among the parasitic in- 
sects. 
They make, no nests for themselves, but intrude upon those 
of various mason and mining bees, and several other insects. 
The Firetail does not, however, lays its eggs in the body of the 
larva, but makes its way into the nest while the rightful owner 
