740 REPORT UNITED STATES GEOLOGICAL SURVEY. 



which serve as a fork to hold the cast skin, covered with excrement, over 

 its body, probably as a protection from its enemies, the birds. The eggs 

 are irregular, flattened, with three spines behind, sometimes, however, 

 wanting, and they are laid on the leaves. The larva matures in three 

 weeks af'ter hatching, molting three times. The larva, when about to 

 change to a pupa, adheres by a mass of silk to the surface of a leaf, with 

 its cast-skin about it. The pupa is smooth, its tail movable, and the 

 limbs, according to Eiley, are soldered to the bodj", as in the chrysalids 

 of moths and butterflies. The pupa state lasts a week. In Massachu- 

 setts, during the last week in July, I have found the larvi3B in all stages 

 of growth very abundant on the morning-glory {Convolvulus), eating 

 holes in the leaves. They pupated late in July and early in August; 

 the beetles appear from the 7th to the 12th. Hand picking is obviously 

 amply sufficient to destroy them if too numerous. 



Description of the beetle. — Of a rich aiuber-yellovr, with a reddish tinge over the body. 

 Two black spots on the back and two on each side, disappearing a few days after cast- 

 ing off the pupa-skin. The wiug-covors are ornamented with finely-impressed punc- 

 tured lines. Body beneath shining black ; autenuye pale on the basal half, dark beyond. 

 Legs pale amber. Length a little less than a quarter (0.22) of an inch. 



The Two-Striped Sweet-Potato Beetle, Cassida hirittata 

 Say. — In the Western States the most common helmet-beetle found on 

 the sweet-potato, and, according to Mr. Riley, feeding exclusively upon 

 it, is the above-named beetle. The grub or larva is dirty-white or yel- 

 lowish-white, with a more or less intense neutral-colored longitudinal 

 line along the back, usually relieved by an extra light band on each side. 

 It differs from the larvse of all other known species in not using its iork 

 for merdigerous purposes. Indeed, this fork is rendered useless as a 

 shield to the body, by being ever enveloped, after the tirst month, in 

 the cast-oft' prickly skins, which are kept free from excrement. The 

 beetle is of a pale yellow, striped with black . (Riley.) Besides these two 

 helmet-beetles, two other species {Cassida nigripes and Coptocyda gut- 

 tata) prey to a certain extent upon the sweet-potato. The cucumber 

 flea-beetle, Epitrix cucumeris (Harris), and a few caterpillars are said 

 by Riley to feed on this plant. Besides these, Harris states that plant- 

 lice sometimes infest the leaves, and to drive them oft" he recommends 

 dusting the leaves with lime. 



INJURING THE ONION. 



The Onion-Fly, Anthomyia cepaTum Meigen. (Plate LXVII, Fig. 1.)— Killing the tops, 

 causing them to turn yellow and wilt; a smooth, conical, white maggot, attacking the 

 bulb soon after the leaves appear early in June, and afterward through ihe summer, 

 and changing to an ash-gray lly, a little smaller than the house-fly, and with a row of 

 black spots along the middle of the hind body, which lays its eggs on the leaves, close 

 to thp earth. 



The onion-fly has been an inhabitant of this country for about forty 

 years, having been imported from Europe. Fitch remarks that "in 

 many parts of New England and Kew York it was extremely numerous 

 and destructive about the year 1854, and again in 18G3." In Essex 

 County, Massachusetts, it has been for a number of years, and still is, 

 very annoying and destructive. Having had little opportunity of ob- 

 serving the habits of this fly, I avail myself of the quite full account 

 given by Dr. Fitch in his Eleventh Report on the Noxious Insects of New 

 York, otten using his own words: "In June, fiS soon as the young seed- 

 ling-onions are oidy an inch or two in height, these insects commence 

 their depredations and continue them through the whole season, getting 

 their growth and coming out in their perfect state one after another, 



