•742 REPORT UNITED STATES GEOLOGICAL SURVEY. 



of these, on the under side of the body, are two additional teeth, like minute feet, 

 by the aid of which the maggot shoves itself forward when crawling. (Fitch.) Speci- 

 mens from Essex County, Massachusetts, are long, conical, the end of the body squarely 

 docked, with barrel-shaped si)iracles ])rojecting from the end of the body. On the 

 under side of the segments are raised folds, one to each segment, and of service in loco- 

 motion. The spirack'S and terminal iou of the tracheai or air-tubes are very distinct 

 on the prothorax, wliile there are no traces of antennte. The fly is like the common 

 house-liy, but smaller and slenderer. The two sexes are readily distinguished from 

 each other by the eyes, which in the males are close together and so Large as to occupy 

 almost the whole surface of the head, while in the female they are widely separated 

 from each other. These flies are of an ash-gray color, with the head silvery, and a 

 rusty-black stripe between the eyes, forked at its hind end. The species is particu- 

 larly distinguished by having a row of black spots along the middle of the abdomen 

 or hind body, which sometimes run into each other, then forming a continuous black 

 stripe. This row of spots is quite distinct in the male, but in the female it is very 

 faint or is often wholly imperceptible. This fly measures 0.22 to 0.25 inch in length, 

 the females being usually rather larger than the males. (Fitch.) 



Remedies. — As a preventive measure worth trial the seed should be 

 sowu two iuches deeper than usual, so that the fly cannot so readily get 

 to it to lay its eggs. Sow also on ground on which straw has been pre- 

 viously burned. Kotation of crops is also a most important preventive 

 measure. When the roots are infested pour boiling water along the 

 drills near the roots, or even on the jdants, going over the bed four 

 times during one season. The diseased onions should be jiulled up and 

 burned. Fitch recommends cultivating the onions in hills, scattered 

 among the other vegetables in the garden. " With only three or four 

 seedlings in a hill it is evident that the young worms could nowhere 

 find a suflicieut amount of food to nourish them to maturity. Having 

 consumed all the young plants in one hill, they will be unable to work 

 their way through the ground to come at another hill except it be by 

 the merest chance, and will thus perish." ' 



The Black Onion-Fly, Ortalisflexa Wiedermann. (Plate LXVII.Fig. 2.)— Infesting 

 the bulb in the Western States ; a more slender, less conical maggot than the Euro- 

 pean onion-maggot, with the head blunter; killing the tops and causing the onions to 

 decay; changing to a black fly, with three oblique white stripes on each wing. 



This native onion-fly was first found to be destructive to onions in 

 Illinois by Dr. Henry Shinier, who writes in the Practical Entomologist 

 (i, 4) as follows regarding it : " In the latter part of June I first observed 

 the larva or maggot among the onions here ; the top dead, tuber rot- 

 ten, and the maggots in the decayed substance. From them I bred the 

 fly. They passed about two weeks in the pupa state. At that time I 

 first observed the flies in the garden, and now few are to be found. 

 Their favorite roosting place is a row of asi)aragus running along the 

 onion-ground, where they are easily captured and destroyed, from day- 

 light to sunrise, while it is cool and wet. During the day they are scat- 

 tered over the ground and on the leaves and stalks of the onions, and not 

 easily captured. Their wings point obliquely backward, outward, and 

 upward, with an irregular jerking, fan-like movement; flight not very 

 rapid or prolonged. They are not very numerous, probably not over 200 

 or 300. All that I observed originated in one part of the bed, where 

 they were doubtless deposited by one parent fly. Two broods appear 

 in a season." 



The Onion-Thrips, Limothrips trUici Fitch. (Plate LXVII, Figs. 3-5.)— Attacking 

 the leaves, causing them to turn yellow and wilt and die; minute, yellow, slender 

 insects, living on the leaves in all stages of growth. 



The following account is taken from my Second Annual Report on the 

 Injurious and Beneficial Insects of Massachusetts: 



"About the middle of August my attention was called by Mr. B. P. 



