PACKAKD.i PARASITES OF NORTHERN ARMY-WORM. 705 



character is the long- compressed abdomen, which, much arched or siclile- 

 shaped, is attached to the bod^' by a slender peduncle. The end of the 

 abdomen is cut off obliquely inwards below. The ovipositor is scarcely 

 to be seen, which in most ichneumons is very long; and here we see 

 the adaptation of this organ to the habits of the species. Instead of 

 piercing- the body of the victim and depositing the egg at the bottom of 

 the wound, the Ophion merely lays its egg on the skin of the caterpillar. 

 The egg is bean-shaped and attached by a pedicle to the skin. When 

 the footless grub is hatched it does not entirely leave the egg-case, but 

 the last joints of its body remain attached to the shell, while it reaches 

 out over and with its sharp jaw-pieces gnaws into the side of the cater- 

 pillar. Some Ophions are parasitic in their ichneumons, just as are 

 the species of Chalcis mentioned below. 



This species, common in Maine, is of a pale-reddish horn color. The head is j'ellow, 

 pale testaceous at the base of the antenna?. The large prominent eyes black. Three 

 smaller black simple eyes are arranged in a triangle aljove, between the compound 

 eyes. The rest of the bodj», especially the hind part of the thorax, and the joints and 

 under side of the abdomen and legs beneath are covered by a bloom of minute lighter- 

 colored hairs which have their origin in microscopic punctures. On the middle of the 

 thorax above, a little darker ; and behind, a yellowish tint. Next the insertion of the 

 abdomen the thorax is thickly and plainly punctate. Same color beneath, except the 

 first three joints of the abdomen, which are touched with yellow, and the lower side is 

 generally darker. 



The veins of the wings are dark ; the thickened cell on the front margin of the fore 

 wings and the adjacent veins as well as the horny triangular pieces in the cell below, 

 the outer of •which is much the smallest, are pale horu color. 



Body nearly an inch long. Expanse of wings, 12|^ tenths. 



Mr. Walsh, of Illinois, has discovered three other ichneumons, descrip- 

 tions of which we take from his pamphlet : 



Mesochorus rilrexs Walsh. — Male, general color light rufous. Eyes and ocelli black, 

 antennas fuscous except toward the base. Upper surface of thorax in the larger speci- 

 men fuscous; intermediate and posterior tibiie with spurs equal to one-fourth their 

 length ; posterior kuees slightly dusky ; tips of posterior tibiaj distinctly dusky. 

 Wings hyaline, nervures and stigma dusky. Abdomen viewed in profile, curves con- 

 siderably, especially at base, and is quite narrow, except toward the tip, where it 

 expands suddenly. The abdomen of the male is appendicniated. It is of a translucent 

 yellowish-white in its central one-third; the remaining two-thirds piccous black, with 

 a distinct yellowish narrow annulus at the base of the third joint. Appendiculum of 

 abdomen composed of two extremely fine setas thickened at their base, whose length 

 slightly exceeds the extreme width of the abdomen. 



The female differs in the head, being from the month upward piceous. The thorax 

 and pectus are piceous black. Ovipositor, which is dusky, slightly exceeds in length 

 the width of the abdomen. Body, .03-.03 inch long. 



Pezomaclms minimus Walsh. — This genus is wingless, like the neuters 

 of ants, except that their antenuie are not elbowed like those of ants. 



Male, piceous. Eyes black, antencfp black, except toward the base, where they are 

 light rufous. Legs rufous, hinds legs a little dusky. Abdomen narrowed ; second and 

 sometimes third joint annulate with rufous at tip. The fenial.o differs in the thorax, 

 being almost invariably rufous, and in the first three abdominal joints being generally 

 entirely rufous, with a piceous aunuliis at the base of the third, though sometimes 

 absent. The abdomen is also fuller and wider. Ovipositor dusky, equal in length to 

 the width of the abdomen. Body .07 to .1 inch long. 



The cocoons symmetrically arranged side by side, and enveloped in 

 floss, are found in the dead skins of the army-worm. A minute ichneu- 

 mon, Chalcis alhifrons Walsh, was bred from the cocoons of the Pezo- 

 maclius. 



Microgaster mUifaris Walsh, is another army-worm parasite. Head black ; palpi 

 whitish ; antennje, fuscous above, light brown beneath toward the base. Thorax 

 black, polished with very minute punctures. Nervures and stigma of the wing fus- 

 cous. Legs light rufous, posterior pair with knees and tips of tibiaj fuscous. Abdo- 

 men black, glabrous, highly polished. Ovipositor not exserted. Length of body, .07 

 inch. 



45 G S 



