REPORT OF THE ENTOMOLOGIST. 291 



will be found preying upon tlie cotton-louse {Aphis gossyjni). The full 

 gT0"wn insect is shown at Fig. 16. It is hrownish in color, with a reddish 

 stripe down the back of the abdomen. The front legs are greatly en- 

 larged and powerfully spined, enabling the insect to hold its struggling 

 prey. From these spines, and those ujion the head, it has gained its 

 scientific name, imdtisjjinosa. 



In addition to these live hemipterous insects, many specimens of a 

 small black and red bug were many times seen about the pupae of Aletia, 

 and were often found within the loose cocoons. Although they were 

 never actually observed to kill the chrysalides, their presence is sus- 

 picious, especially as upon examination their beaks were found to be of 

 the short, broad, predaceous type. All of the specimens forwarded to 

 the department were of immature individuals, from which it was impos- 

 sible to ascertain the species. They were flat, nearly round, a trifle over 

 one-tenth of an inch (S""") in length. The head and thorax were black j 

 the abdomen had a broad red baud around near the margin, and three 

 narrow transverse white bands. 



Although we have several parasites on the cotton-worm belonging to 

 the next order, Dipteea, the only predaceous insects from this order 

 are the Asilus flies. 



AsLLUS-FLiES OR EoBBER-FLiES (Dipt. fam. AsUiidae). — The large 

 buzzing fly, with long slender abdomen and thick hairy throat, is a 

 familiar sight in the cotton field to the observing planter. A popular 

 name was never more appropriately apjAied than that of robber-flies 

 {^^ rauhjiiegen^^), given to these flies by the Germans, 'ihey are among 

 the most rapacious of insects ; but not only axe they as indiscriminating 

 as other i)redaceous insects, but some species seem actually to prefer 

 beneficial insects as a steady diet. There is almost no enemy which the 

 apiarist fears more than these "bee-killers," as some species are termed. 



Mr. Thompson, in an article in the Kural World for September 12, 

 18G8, stated that he had observed one individual Asilus-fly to destroy 

 141 bees in one day. 



Thi'ee species have been captured in the cotton fields of Alabama. 

 These are Erax apicalis, Wied., Diogmifes diseolor, Lw., and Dionyzias? 

 sp. Bj' far the most abundant species was JErax apicalis^ Wied. This 

 species (represented by Plate XI, fig. 3) varies from an inch to an inch 

 and a quarter in length (25 to 32"-'"), and has a wing expanse of nearly 

 an inch and a half. The abdomen is black, with silvery markings above 

 and whitish below. The top of the thorax is yellowish- white and brown 

 above, as seen in different lights. The legs are spiny and light-brown 

 in color and the face is nearly white. In the summer of 1878 I observed 

 large numbers of these insects flying around the cotton fields in the 

 vicinity of Selma, Ala., occasionally darting to the ground and seizing 

 some insect. With some difficulty a specimen was captured while 

 engaged in sucking the juices of a young grasshopper (Galoptenus sp.). 



During the past summer Mr. Trelease forwarded several of these 

 insects to the department from Miu-ter, Dallas County, Alabama. He 

 stated that they were very abundant in the cotton fields, and had been 

 several times seen to catch the cotton-moth on the wing and devour it. 

 The rapacity and the capacity of these flies have been seen in the statement 

 of I\Ir. Thompson ; and even supposing each individual in the southern 

 cotton fields in the course of a day to kill cotton moths in numbers that 

 shall seem small in projiortion to the number of bees which Mr. Thomp- 

 son actually saw them kill, we shall be obliged to put them down as 

 among tlic very best friends of the planter. The benefits derived from 

 the abundance of this insect will, however, be greatly detracted from 



