290 THE CANADIAN ENTOMOLOGIST. 



trees and slirubs : Ai)ple, ])lum, pear, wild red cherry, grape, currant, 

 rose, maple, })0plar, ash, birch, and various others. 



In order to combat this scale, it is first absolutely necessary that one 

 should be well acquainted with its life-history. 



* Life-history. — This minute insect, found upon the bark of the small 

 twigs and also upon the branches and trunks of the above-mentioned trees, 

 is readily identified by its oyster-shell-shaped scale, about one-sixth of an 

 inch in length. It is of a brown colour, and, thus disguised by the bark, 

 is not seen unless by close observation. Usually a good many are 

 clustered together, and their shape is so marked that orchardmen should 

 soon recognize them. These scales sometimes cover tvvigs and large 

 brcUichcs completely ; even the leaves are ulten infested, and sometimes 

 the (ruit ilselt becomes mure or less covered. J vast year the huil on 

 se\-ei;il M;i,ic1ei)\s Ulush ajtple Irecs L;ro\vn in l.lie ore liaid of the ( ). A. (J, 

 war; noticed to be affected by the scale. This, however, is the exception 

 rather than the rule. 



This insect is one-brooded, and winters over in the egg stage. The 

 eggs can be easily seen if at any time in the fall or winter the old scales 

 be lifted up and examined beneath. Numbers of very small whitish- 

 yellow eggs will be seen. Here beneath this oyster-shaped scale they 

 remain until early in the summer. The young yellow lice escape from 

 the eggs during the last week in May and the first week in June; that is, in 

 the vicinity of Guelph. They wander for a few hours, or a few days, on 

 the limb, then settle down and secrete a scale. They fix themselves upon 

 the tender bark, which they pierce with the beak-like structures con- 

 nected with their mouths, and by means of which they are able to suck 

 the sap from the tree. The larvae moult, or shed their skins, twice in the 

 course of their growth during the summer. These moults can be readily 

 seen on the narrow end of the large scale. The adult female dies soon 

 after the laying of the eggs, about 5o in number, in the fall. They may 

 be spread from tree to tree to some extent by birds, and also by other 

 insects. 



Such is the life-history of the Oyster-shell Bark-louse, and before 

 entering into a discussion as to the best means to adopt for its eradication, 

 it will be as well to briefly mention and describe one or two other species 

 of the commonly-occurring scales which most closely resemble it, and to 

 point out the differences for this purpose cuts are given with the various 

 scales. 



