I am frequently asked concerning the origin of the peculiar egg-like objects often seen on the backs of tomato-worms, and shown in the accompanying illustration. These are not eggs, however, but are the cocoons of a little parasitic fly which is an enemy of the worm, and the way in which they originate is as follows ; Some fine summer day, when the tomato-worm is enjoying his meal of the leaves or fruit of the tomato, a small, black four-winged fly alights upon his back, and deposits beneath his skin by means of a long needle-like instrument called the ovipositor, great numbers of minute eggs. In a few days these eggs hatch into little legless grubs which absorb the juices of the worm and develop at his expense. In a few weeks the tomato-worm stops feeding - its body being literally full of the grubs. When full grown, these grubs bore holes in the back of their host and crawl through the skin and escape. As soon as they are on the outside, they begin spinning white silken cocoons, which are the objects frequently mistaken for eggs.

Within these cocoons they change to the pupa state, and in about a fortnight emerge as four-winged flies like those by which the original eggs were laid.

Tomato-worms, affected by these parasites, seldom live to change to the pupa state, and never, so far as known, complete their transformations.

But these little parasites do not always have things entirely to their liking, for they are themselves subject to the attacks of a still smaller parasite which destroys primary ones - differing both in form and color. Th s them as they destroyed their hosts. These secondary parasites, as they are called are quite different from the species of primary parasite which attacks the tomato-worm is called by entomologists Apanteles congregatus. It is black, while the secondary species may be either yellowish-brown or brilliant bluish green.

Tomato-Worm With Cocoons Of Parasites.

Anyone can get these parasitic flies by enclosing some of the cocoons in a box or other receptacle.

Clarence M, Weed.