1891.] 2G7 



the sides ; the abdomen is conico-cylindrical, verj glabrous, and has all the setsc 

 large, and those on the fourth segment very numerous ; tlic wings liavc the fourth 

 longitudinal vein bent at rather a rounded angle, and the outer cross vein a little 

 curved, but not usually sinuous ; the legs are black, and armed with numerous 

 strong spines irregularly arranged. Not common. 



{To be continued), o J^ /" 



ON THE ALTEEATION IN THE FORM OF THE SCALES OF LECANIA 

 CAUSED BY INTERNAL PARASITES. 



BY E. NEWSTEAD, F.E.S. 



Last year, when examining a number of specimens of Lecanium 

 fiiscum, I found among them a single one almost as large again as the 

 rest, and of a different form ; so much so, that I considered it a 

 distinct species, until upon removing it from the branch for closer 

 examination I saw in it some parasitic larvje, and as this was the only 

 example that contained such larvae, the thought occurred to me that 

 the form of the scale might have been abnormally altered by the 

 parasites. I communicated my observations to Mr. J. "W". Douglas, 

 who replied that my statement was important, but required further 

 proof. 



This year I have examined a good many species of Lecanium, and 

 find that several are subject to considerable variation in the form of 

 the scale, and this entirely from the attacks of internal parasites. Of 

 these there are at least two species very common, and both, so far as 

 I have been able to trace, produce abnormal swellings, peculiar to the 

 species, on the dermis of the host. The most important of these is 

 that which produces one, two, or more large tubercular swellings — • 

 generally two ; when the latter is the case the scale appears quite 

 symmetrical, one of the swellings being on either side of the dorsum 

 each opposite to the other. When there is but one large tubercle, it 

 is invariably situate on one side of the dorsum, thus giving the scale 

 a "lop-sided" appearance, which at once attracts the eye as curious 

 and unusual. I find that each of these tubercular swellings, if ex- 

 amined in season, as a rule contains a single parasitic larva, or if more 

 are present, there is but one large swelling, which gives the scale a 

 heaped-up or gibbose form. Such forms I find common in the follow- 

 ing : — Lecanium (ssculi,fuscum, genevense, and caprece, especially in the 

 two latter. I should add that the portions of the dermis affected by 

 the parasites are devoid of the ordinary reticulation, and iu the speci- 



