PETTIT ON SCALE INSECTS OR COCCID^E. 81 



The (litfcrent jionera of iliis larjie snh-fsiniily are separated by tlie form 

 of the scales and the i)hice occniiit-d liy their east skins. Tims in 

 Aspidioliis, the male and female srales ai-e more or less roumh'd, — the 

 male stale sometimes slijihtly elongated. — of the same texture, and 

 havinji" as tlie main difference the possession of two cast skins by the 

 female and only one by the male. 



ni<isjtis has the female scale rounded, with the exuviae more or less 

 central and the male scale while, elonjiated and more or less carinated. 



ChioiKisiHs lias the fenuile scale elon<»ate with tlie cast skins at the 

 cephalic end. The male scale is white, elon<>ated and often carinated. 



.^fi/lilixpis has Ihe scales of male and female similar in form, both 

 bein^- elongate ami seldom either of them white. The cast skins are at 

 one extremity of the scale. 



Parldtoiid has a female scale rounded or elongate, with the second 

 cast skin usually larjie and not ]U'Ojectinji' much Ix'vond the cephalic 

 end of the scale. The male scale is white and not carinated. 



Uhleria resendiles Parlaforia but the female has the second cast skin 

 covered with secretion. 



Study of the insect itself under the scale shows that each j^-enus has a 

 distinct type of structure, and after one becomes familiar with the 

 diftVi'ent oenera, these structural characters of the insect itself are 

 used to help settle the genus, for the characters given here have some 

 exceptions and the different genera run into one another somewhat. 



Sj)ecitic determination is based largely on the characters of the 

 caudal segment of the female together with the appearance of the scale. 

 An examination of the caudal segment of the female shows a more 

 or less intricate arrangement of plates, spines, and lobes, into a fringe 

 on the hinder border. This arrangement holds pretty constant with 

 each species and while there is variation to a certain degree, usually 

 it is not very great. A study of this fringe requires a compound 

 microscope with at least a one-eighth objective, and for settling some 

 points a one-twelfth is very desirable. Specimens are usually mounted 

 in balsam after boiling in potassic hydrate to clear them. 



A discussion of the different species in Michigan would take a long 

 time and will not be attempted at this time, suffice it to mention one 

 or two. 



The San Jose scale, Aspidiofus perniciosiis, was discovered to be in 

 ^lichigan in 1S96 and since that time has been found in a number of 

 localities. It lives on a large number of different plants, including fruit 

 trees, forest trees, shrubs, etc., even working at times on strawberry 

 and grape vine. It spreads very rapidly and affects trees very seriously, 

 ordinarily killing them in a few years if no remedy is applied. 



The European Fruit scale, A. ostrca'fonnis, was discovered in Michigan 

 about a year ago although it has been here for eight or ten years. It 

 works much as does the San Jose scale but seems to be less dangerous, 

 not killing the hosts outright so often as the San Jose. It is, however, 

 a serious pest and worthy of careful treatment. 



The sub-family, Lccanin((\ differs in many ways from the Diaspinrp. 



Its members ])roduce no protecting scale and possess no fringe on the 



caudal segment. There is instead a cleft extending some distance from 



the caudal umrgin and two triangular scales at the cephalic end of 



11 



