244 EEPOKT OF THE COMMISSIONER OF AGRICULTURE. 



(1) Tlie simple water suspension of pyretlirum in fonr tests on pupte 

 was tried with a mortality of 10 per cent., but on the winged Cicadas, 

 both soft and hard, it was thoroughly fatal, like the powder. 



(2) Pyrethrum powder, one-eighth pint; milk, 1 pint; water, IG i)ints, 

 mixed. 



Fifteen pupa3 were treated with this with the following results: Oiic 

 disappeared, six died as pupse, five died half emerged, and three emerged 

 apparently uninjured. The same preparation sprayed on mixed lots o!" 

 pupa3 and winged forms, soft and hard, on trees and on the ground, had 

 similar effects on the i)upai and killed all the winged insects. 



In this way a very strong mixture of pyrethrum is ajiplied, and it 

 should be stirred just before using, when it will kill most of the i>upai 

 as well as the emerged forms. 



Kerosene Emulsion. — This was prepared after the usual formula and 

 diluted with two x)arts of water. 



Used on a mixed lot of pupae and adults, soft and hard, one hundred 

 of these on the base of an uninfested tree and fifty in the grass, 8 feet 

 distant. In five minutes all seemed weakened : the pupas still crept 

 along a little, but the winged ones hung immovable on the tree or lay 

 upon the ground, only moving their legs a little in a weak and helpless 

 manner. A few minutes later the pui)iB had stoj^ped creeping. This 

 was at 7 a. m. At noon they had not moved from their places, except 

 by a few having dropped from the tree, and all were either dead or 

 nearly so. The emulsion at once stopped all molting and transforma- 

 tion, and the soft wings hardened in shapeless forms. The same effects 

 on the insects resulted in several smaller tests of the same strength of 

 emulsion, though niany of the insects were twenty -four hours in dying. 

 The pupre were the slowest to succumb, but they were all destroyed by 

 it in every instance and could not molt. Sprayed on them on the ground 

 and as ascending or hanging on trees the same results followed, and 

 this dilution of the emulsion seems the most thorough destroyer of the 

 pupce as well as of the emerging and winged Cicadas. From a whole 

 pint of pupiB sprayed by this mixture not one suceeded in transforming. 



Small ants usually attacked some of the Cicadas that were struggling 

 under the effect of pyrethrum. or dead from it, but no ants were found 

 affecting specimens treated with kerosene. 



Other experiments were tried with the same emulsion, diluted as fol- 

 lows: (1) Emulsion, 1; water, 4; and (2), Emulsion, 1 ; water, 8. 



The two strengths sprayed on groups of pupoe gave results that 

 varied from each other but little and killed nearly all; but some were 

 very slow to die and showed life even after two days. 



Sprayed on the ground or the trunks of trees, these dilutions did 

 not prevent the pupie from ascending, and apparently had no effect on 

 them except when sprayed on their bodies. 



SUESTAXOES THAT KILL BY THWARTING EXUVIATION. 



Dr. Barnard concluded from his tests that by communicating to and 

 retaining moisture or softness in the pupa skin, even theniilk and water 

 in the preceding mixtures tend to render it difficult or impossible to 

 cast the skin, and that they thus aid pyrethrum or kerosene. 



CarhoUc acid (2 per cent, solution). — This prevents the majority of 

 pupte from molting, and they die sooner or later. For example, wlieu 

 applied to one lot of pupoe at night, five were found in the morning 

 dying or dead in a half-molted condition ; seven were active, not molted, 

 and apparently not suffering ; one was molted, but turned black by the 

 acid and dead. In another case five dozen pupaj on the base of an uu. 



