7 



under the respective names of Persian and Dalmatian Insect Powder; the former is the 

 powdered flowers of Pyrethrum roseum, the latter of Pyrethrum cinneraria-foliwm. The 

 Dalmatian Powder is most highly esteemed. The powder is diffused through the atmos- 

 phere by means of a small bellows, or insect gun, and in a very short time it brings house- 

 flies, cockroaches, etc., on their backs, and dusted among bed-clothing is equally effec- 

 tual on noxious pests there. It does not at first kill the insects outright, but paralyzes 

 them so that they are unable to use either legs or wings, and after remaining in this 

 condition many hours and sometimes days, a solitary individual here and there will 

 either wholly or partially recover, but the great bulk of them die. 



A very active blue-bottle fly placed under the influence of the powder was brought 

 on its back in one and a half minutes. After six minutes it performed some remarkable 

 evolutions, throwing itself about in the most desperate manner by the aid of its wings, 

 for by this time it had lost the use of its legs ; in a few moments more it was quiet, but 

 still able to move its legs, and this power it retained for two days, after which it was lost 

 sight of. The same powder was applied to a full-grown grasshopper ; immediate un- 

 easiness was manifested, and within two minutes its hind legs were partially paralyzed 

 so that they could not be used with much effect. The first symptoms were a general 

 rubbing of the legs against each other and a peculiar backward movement of the body ; 

 in four minutes there was a trembling of the whole frame, while all the legs were so 

 much affected that locomotion was very feeble. In six minutes the insect' had lost all 

 control over its limbs, and in nine minutes it was on its back, with no power to recover 

 its natural position. A second patient manifested precisely similar symptoms, but was 

 not affected quite so rapidly. Applied to house-flies in a room, some of them begin to 

 fall powerless in two or three minutes ; others will remain active several minutes longer, 

 but manifest constant uneasiness, evidenced in unnatural movements of wings and legs, 

 and a frequent thrusting out of the proboscis. Having operated in a room one day about 

 noon, I swept up after a few minutes several hundred flies and put part of them in a 

 tumbler covered with a small plate, and the remainder in a chip box which I carried in 

 my pocket for the first day, where the flies would receive some warmth from the body. 

 After five or six hours the box was opened, when several crawled out or flew with a very 

 weak, short flight \ these were evidently recovering ; the others remained on their backs, 

 many of them moving their legs now and then. At the same time those in the tumbler 

 were looked at ; all were on their backs, but still alive. In twenty-four hours after- 

 wards those in the glass were in the same helpless condition, barely alive, while in the 

 box three more had so far recovered as to be able to walk, and one of them could fly a 

 little. The following day they were examined again and every one of those in the box 

 were dead, while in the tumbler, out of 137, there were 22 alive, which number was 

 reduced to three the following day; this small remnant survived two days longer, when 

 all died. 



In the use of Insect Powder on the green Aphis, which infests house plants, the 

 same course was observed ; the insects dropped from the plants as if paralyzed, and 

 after a short time were incapable of locomotion. After two days they were found still 

 alive, but in this instance there was no sign of recovery in any of them, and all died 

 within two or three days afterwards, but whether from the direct effects of the powder or 

 from starvation I was unable to decide. 



When I addressed you last year I referred to a strange disease which had destroyed 

 large numbers of that destructive pest, the Forest Tent Caterpillar, Clisiocampa sylvat- 

 ica. After the disease had reached a certain stage the larvae remained motionless, re- 

 taining their hold on fences and the trunks of trees ; shortly, although in appearance 

 they were quite natural, when touched they were found to be dead, and their bodies were 

 so decayed as to burst with a very gentle handling. Subsequent observations convinced 

 me that this was the result of a fungoid disease to which caterpillars, as well as some 

 perfect insects, are very subject. A similar disease sometimes attacks the silk-worm 

 and causes great devastation, and the common house-fly is liable every autumn to die 

 from the effects of a fungus which multiplies with amazing rapidity within the fluids of 

 the fly's body, soon destroys life, and forms a circle of luxuriant growth all around its 

 victim. Examples of this may be found on the windows of almost every dwelling during 



