104 ENTOMOLOGICAL SOCIETY. 



ODOUR OF THE SAN JOSE SCALE, Aspidiotus perniciosus 



By F. M. Webster, Wooster, Ohio. 



In the many accounts of this insect I do not recall that attention has been called to 

 the odour that is associated with this insect and which in cases of excessive abundance, 

 can be detected at a considerably distance away. Where the air is quiet it is often 

 possible to detect the presence of a badly infested tree a yard away, and I presume that 

 with more acute olfactories, such as insects are supposed by many to possess, even the 

 presence of a more limited number of the scale might be detected at a much greater 

 distance. As ants do not appear to be at all partial to this Coccid, at least in this 

 country, it is not easy to understand what influence this odour can have in the economy 

 of the species. It is possible that, in its native home, this odour might attract other 

 insects and thus aflord a means of diffusion, not at present so available to the scale in 

 this country. 



The Odour of Coccid^. — Prof. Webster's interesting note leads me to offer a few 

 remarks. The species of the subgenus of Toumei/ella of Lecanium have quite a strong musky 

 odour ; but ordinarily I have been unable to detect any marked odour in Epeciea of 

 Ooccidae. I suppose, however, that all possess some odour, and that its purpose is to 

 attract the males to the females. This seems the more probable when we remember that 

 in many species the male puparia are not on the same part of the plant as the females. 

 Here at Mesilla Park, also, I have lately seen a male of Mar gar odes hiemalis, Ckll. ined , 

 run over the ground until it detected a spot where a female was buried, and then dig 

 down to the female. It must certainly have detected its mate by the sense of smell 



T. D. A. Cockerell. 



LIFE HISTORY OF THE SHEEP SCAB-MITE, Psoroptes communis. 



By C. P. Gillette, Fort Collins, Colorado. 



I am not aware that the full life- history of this insect has been published, though I 

 shall not be surprised to learn that such is the case. 



In order to know how long a time should intervene between the first and second 

 dippings for the cure of scab, we must know the period of incubation and also the entire 

 time elapsing from the deposition of the egg up to the time that the mite from that 

 egg, if a female, may be itself depositing eggs. These points were determined in a series 

 of experiments conducted by the writer one year ago and were reported in a local paper, 

 the " Fort Collins Courier," last spring. I took seventy-five eggs from a lock of wool 

 drawn from the back of a badly infested lamb and, after dividing them in two nearly 

 equal lots, placed them at once on the skin of the backs of two lambs that were not 

 infested with the mites at the time. In order to irritate the surface a little and better 

 prepare it for the little mites that would begin at once to hatch, a lock of wool was 

 drawn in each case from the particular spot where the eggs were placed. 



Mr. Ball, assistant in my department, made a special examination of these "cul- 

 tures " once a day until the mites from the eggs were fully grown and themselves laying 

 eggs. 



At the first examination a few young mites were found, which was to be expected 

 as a few eggs among so many would be about ready to hatch. At the end of the fourth 

 day all the eggs had hatched. At the end of the ninth day a few individuals were found 

 in copula, and on the eleventh day eggs were found. As it required four days for the 

 newly deposited eggs to hatch, the entire time elapsing from egg to egg would be fourteen 

 or fifteen days. 



As there would be eggs in all stages of incubation upon a sheep when the latter is 

 dipped for the cure of scab, I have set the limit of time for the second dipping at not 

 sooner than five days and not later than ten days after the first dipping. If the second 

 dipping comes at a time outside this limit, there will probably be eggs upon the sheep 

 again. 



