THE AMERICAN ENTOMOLOGIST. 



193 



ages are in two groups, one on either side 

 of the chest (thorax). Five primary trunks 

 arise together, each, except one, dividing 

 immediately to form a pair. They rise in 

 a diverging, somewhat curved manner, and 

 are about one-half as long as the body of the 

 pupa, which differs from the others described 

 in having nine horns on each side of the 

 thorax. I'he chitine walls of these prongs 

 are finely porous. I have detected them 

 already in the larva beneath the skin fully 

 formed of epithelial cells, which have hot 

 yet deposited the chitine layer. They all 

 arise from the same spot, and I have found 

 them to be branches from a single internal 

 tube, a part of which is seen within the 

 molted pupal skin. This stigma-tube 

 from which they arise has a diameter 

 about equal to that of any individual 

 prong near its base. Like the air-tubes of 

 other insects it is composed of chitinous 

 ring-fibres, etc. Thus I have settled be- 

 yond doubt the nature of these para,doxi- 

 cal appendages of the Simulium. They 

 are respiratory organs of the nature of 

 tracheal gills. 



The larval skin is found crammed in by 

 the side of the pupa, and finally the pupa 

 skin is left with it. 



The length of the adult is a trifle over 

 4"""' (5-32 of an inch) ; color, dark brown ; 

 legs, lighter brown ; balancers and basal 

 half of each rear heel (ist tarsal), white ; 

 abdomen, blue-gray beneath and toward 

 the sides ; antennae tapering somewhat 

 toward the distal end. 



THE USE OF PYRETHRUM. 



THE EDITOR. 



Since we found, in 1878, that Pyre- 

 thrum powder was so thorough and effect- 

 ive in killing the Cotton Worm, and par- 

 ticularly since the favorable results ob- 

 tained by its use in the open cotton field a 

 year ago, as shown in our February num- 

 ber (p. 43), we have had a firm belief that 

 it is to be the insecticide of the future, 

 and that instead of the thousands of tons 

 of Paris green, and other poisonous and 

 dangerous arsenical compounds that have 



been sold all over the country, for use 

 against the Colorado Potato-beetle, the 

 Cotton Worm and other great insect 

 pests, we shall soon have this Pyrethrum 

 extensively cultivated and used. The sole 

 objection to it now is the cost ; and while 

 those who manufacture it, and put it on 

 the market in small powder packages, 

 would like to monopolize its growth and 

 production, they cannot long do so. It 

 grows almost as easily as Mayweed, or 

 Ox-eye daisy, and we have taken steps to 

 have it tested and introduced in several 

 different sections. 



Having, a year ago, commenced a series 

 of experiments which are being continued, 

 we shall report the results, from time to 

 time, and commence with the following 

 notes of a series made in July, 1879, ^1^" 

 der our direction, by Mr. W. A. Henry, of 

 Ithaca, N. Y. : 



EFFECTS OF THE POWDER. 



On Flea-beetles. — July gth. — Tried 

 the powder on young cabbage plants, for 

 the purpose of driving off the Flea-beetles, 

 which were very numerous, having entirely 

 ruined many plants. Dusted the powder 

 over the plants, but do not find it very 

 effective, as the fleas are on the under side 

 of the leaves, and difficult to reach. More- 

 over, the powder does not adhere well to 

 the glaucous leaves. The insects spring 

 away upon dusting the powder over the 

 leaves, and many evidently escape without 

 carrying any of it with them. Did not 

 observe that the powder affected any of 

 them. 



July 2ist. — Found the powder still upon 

 the plants. (There has been no rain, and 

 but little dew in the interval.) 



Only two Flea-beetles were found, and 

 these were on the under side of the leaf. 



On Blister-beetles. — July igth. — 

 Found the Striped Blister-beetle defoli- 

 ating a large Passion Flower vine. Upon 

 applying the powder, the insect was at 

 once affected, and began to make vigorous 

 efforts to remove the irritating substance 

 by rubbing the legs against the body. In 

 less than three minutes, however, it is un- 



