INSECT ENEMIES. 117 
appearance in the larva state. The name Blennocampa 
signifies a slimy caterpillar. Its favorite trees are the 
pear, cherry, and quince, and it is sometimes found on 
the plum and mountain ash. Ordinarily there are but 
few on a leaf, but sometimes the leaves are fairly spotted 
with them. Thirty have been counted on a single leaf. 
Professor Peck, of Massachusetts, wrote its natural history 
in 1790 with such critical accuracy that litt!e has been 
since added to our knowledge of its life history. It is 
now quite generally spread over the country. ‘This slug 
comes from the eggs of a saw-fly, about one-fifth of an 
inch long, resembling the common house-fly. Its body 
is glossy black. The first two pairs of legs are clay- 
Fig. 104.—Female, Fig. 105.—Zarva. 
PEAR-TREE SLUG, 
colored, with dark thighs. The hind legs are dull black 
with clay-colored knees. The wings are transparent, 
slightly convex, and uneven on the upper side, with 
brownish veins. They reflect the changeable colors of 
the rainbow, with a smoky tinge in a band across the 
middle of the first pair. 
The female is provided with a saw-like appendage, 
with which she cuts a curved incision through the skin 
of the leaf, in which she lays her eggs singly, and gener- 
ally on the under side, from about the middle of May 
into June. In fourteen days they begin to hatch. At 
first the slugs are white; but soon a slimy matter oozes 
through the skin, and covers their backs and sides with an 
olive-colored, sticky coat. The head is small, of a dark 
