48 LETTERS ON ENTOMOLOGY. 
grubs come out through the skin, sometimes to 
the number of fourteen or fifteen, yet the poor 
insect sometimes survives, and even turns to a 
chrysalis, though it does not become a butterfly. 
The most beautiful of the cabbage caterpillars is 
the most subject to be attacked by the gregarious 
grubs, which, after their coming out, spin them- 
selves up in cones. 
If we examine the elm or oak caterpillar, we 
shall frequently find one or two little white 
patches, which are usually placed between the 
rings. Examined with a microscope they ap- 
pear to be eggs ; but they are so firmly attached 
to the skin, that it comes off before they can be 
separated. Reaumur closely inspected one which 
he detached with care, and found a hole on the 
part next the skin. He afterwards dissected the 
caterpillar, and found in it a large grub. 
Some have these creatures outside in different 
parts of the body, sometimes to the number of 
twenty. They appear to bury their heads in the 
skin, and some spin their cones on the body of 
the caterpillar. Some flies even deposit their 
eggs in the eggs of the butterfly, and thus the 
latter are devoured before they are born. 
Another formidable enemy is a black shining 
grub, which becomes as large as a middling cater- 
