88 MASSACHUSETTS HORTICULTURAL SOCIETY. 



scale insects become so hard-bodied, and tlieir integument is com- 

 posed of such solid chitine, that they are practically as resistant 

 to the action of washes as are those species which have a dense 

 scale of wax. A better classification, when we are considering 

 the matter of remedies, is to divide the group into those species 

 which give birth to living young and those which lay eggs. The 

 object of this division will be at once apparent. Those scale 

 insects which give birth to living young, drop a number of young 

 per day for a comparatively long period. Those first hatched 

 become resistant to the action of washes within a few days, so 

 that at no one time do we have even a majority of the insects in 

 the young and unprotected condition in which washes, weak 

 enough to do no damage to the foliage, will kill them. With the 

 scale insects which lay eggs, on the contrary, there is a more or 

 less definite hatching period. In other Avords, all the eggs in a 

 given generation hatch at approximately the same time, and the 

 majority of the young are in a condition to be killed by weak 

 washes at about the same time. The species that give birth to 

 living young can therefore be treated to advantage only in the 

 winter, when there will be no danger of injuring the foliage of 

 the trees by the action of washes which are strong enough to 

 kill the insects under their scales.' The best example of this class 

 is the San Jose scale. The egg-laying species, as exemplified by 

 the common oyster-shell barklouse of the apple, pass the winter 

 (most of them) in the egg condition under the old mother scales. 

 They hatch, approximately all together, the latter part of May 

 or in June, and at this critical time may be destroyed by the 

 dilute kerosene emulsion. 



Let us hurriedly, then, take up a number of species, all of which 

 Massachusetts fruit growers should know. But a few Avords 

 need be said about each, since the illustrations on the screen and 

 the specimens which I shall exhibit afterwards, will convey a 

 more definite idea of the appearance of the insects than any 

 words of description. 



The lecturer next gave a brief account of the following species, 

 of some of which engravings from the publications of the 

 Department of Agriculture are here presented : 



The San Jose scale (Aspidiotvs 2^ern!ciosifs), Fig. 1. 



Oyster shell barklouse of the apple {Mytilaspis ^lomoru m) ,Y\g. 2. 



