300 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



The insects bred from tbese specimens were small, black, chalcid flies, 

 shown at Plate XIII, fig. 2. They were nearlj- eight-hundredths of an 

 inch (2'"'") in length. The general color was black, but the legs, anten- 

 nae, and mouth parts were honey -yellow. The head, thorax, and abdo- 

 men were nearly equal in width, and the thorax was longer than the 

 abdomen, which was pediceled and subtruncate at tip. The antennae 

 were 7-jointed. 



The larvae were greenish white, oval, somewhat pointed at one end, 

 with yellow spiracles or breathing-holes, and were fleshy and footless. 

 They were sluggish in motion, moving by the alternate contraction and 

 expansion of the segments. The number of segments of the body was 

 plainly thirteen. The full-grown larvae were about 0.08 inch or 2™" in 

 length, and were about half as wide as long. The cocoons which they 

 spun were ovoid in form, grayish- white in color, and about the size of 

 the full-grown larvae. 



The proctotrupid parasite of the cotton-worm {Didyctium 

 zigzag, Riley). — September 10, 1879, a number of small parasitic flies 

 issued from chrysalides of the cotton-worm. Upon examinSition these 

 proved not to be Chalcids, but to belong to the allied family Proctotru- 

 indae. The members of this family dilier from the Chalcids in their usu- 

 ally slender body and longer antennae. The antennae, also, are not 

 elbowed as in Chalcididae. It is a family of very minute species, which 

 are all supposed to be parasitic, many of them upon the eggs of other 

 insects. 



The species under consideration is shown at Plate XIII, fig. 3. These 

 flies are black, polished, with the antennae and legs dark yellow. The 

 antennae of the female are 13-joiQted, the first joint club-shaped, the sec- 

 ond almost globular; 3 to 7 are much thinner than any of the others; 3 

 about as long as 2 ; 4 to 7 almost globular; 4 a little thinner at base ; 8 

 to 12 about equal in size, round at base, and squarely cut off at apex ; 

 13 as long as preceding, ending in a rounded blunt point. The antennae 

 of the male are very long, about as long as the whole insect. The wings 

 are clear and sparsely beset with short, blackish bristles, and with quite 

 a long fringe around the edge. The veins of the wings are yellowish. 



These insects are about .06 of an inch (1.5"™) in length. 



These parasites were bred only upon a single occasion. Then many 

 specimens were mounted. Whether they were all from one chrysahs or 

 not it is impossible to say with certainty, but the probabilities are that 

 they were, and it seems probable also that it is not a common parasite.* 



The next three parasites which we shall mention belong to the family 

 Ichneiimo7iidae, or ichneumon flies, as they are commonly and famiharly 

 called. These insects are characterized by unusually long and slender 

 bodies and the long projecting ovipositors of the females. These ovi- 

 positors are often very long, and are protected by a sheath of four stylets 

 of the same length as the true ovipositor. Then head is usually rather 

 square, with long many-jointed antennae. The larva is a soft, cylindri- 

 cal, fleshy, white, footless grub, the rings of the body being convex and 

 the head small. The eggs are laid by the parent either on the outside 

 or within the caterpillar or other larva upon which its young is destined 

 to feed. Vv'hen hatched, the larva devours the fatty portions of its 

 victim, just as we have seen with foregoing parasites, until it gradually 

 dies. The larva spins a cocoon about itself when about to enter the 

 pupa stare. In the larger species this cocoon consists of a dense inner 

 case, and a loose, thin outer covering. Of the larger species but one 

 individual occupies the body of the host, whil e in the sm aller species 



* For teclinical description see special report, p. 197. 



