INSECTS ATTACKING WEEDS IN MINNESOTA. 147 



Natural Enemies. — Several egg parasites were reared on June 

 24. Mr. Girault of the United States National Museum identified 

 the parasite as a new species of the superfamily Chalcidoidea. He 

 named it Aprostectus luhitmani. 



The Sunflower Stem-borrer ( Stniussia Io)!gipciiiiis, Wd.). 



Life History. — The adult flies were first observed on June 1, 

 while on June 3 they were ovipositing. The eggs are laid in the 

 stem, one or two inches from the top of the plant. Upon hatching, 

 the larvae travel down the pith of the stem so that in late summer, 

 they are found mining in the pith at the base of the stem or in 

 the roots. Full-grown larvae were found the last week in August. 

 When the larvae reach the roots, the plant may begin to topple 

 over. There is but one generation a year and the winter is passed 

 in the pupal stage within the stems. 



Egg. — 1 mm. X 0.3 mm.; greenish-white; elongate; posterior 

 end tapers somewhat more than anterior end, which is provided 

 with a very small, transparent pedicel. Egg smooth all over. 



Oviposition. — Oviposition habits are essentially as recorded by 

 Lintner, who gives the only record of its food plant. When about 

 to oviposit, the female runs up and down the top of the stem, with 

 wings expanded. She then l)ends her body and inserts her long 

 ovipositor in the stem one or two inches from the top, for about 15 

 or 30 seconds. Egg punctures appear as small, elongated, discol- 

 ored areas, and if the stem is cut open at one of these points, the 

 egg will be found lying obliquely in the middle of the stem and 

 very conspicuous. 



Larva. — Length, 8 mm. x 2 mm. wide; elongate, greenish-yel- 

 low. Two great hooks. The anterior spiracles are funnel-shaped, 

 composed of a double row of about 14 lobes, each of which in turn 

 appear under high power to end in a semi-circular chitinous area. 

 The stigmal plates are about their diameter apart, each composed of 

 three straight, elongate slits. These are arranged less radially than 

 in other Trypetidae, the two upper ones being parallel, while the 

 lower one is directed towards the middle one, is closer to it, and 

 extends farther towards the center. The anal tubercles are small, 

 somewhat truncate and situated below the stigmal plates at a dis- 

 tance less than the width of one of them. 



