THE BRITISH NATURALIST. 



2 5 



begin to spin a covering or " scale " by means of a series of important 

 but very minute organs known as " spinnerets," shown in Fig. 7. 

 According to some observers they do not remain stationary and spin 

 their scale directly behind them or around them, as a 'woolly aphis would 

 do, but advance during the process of forming the scale. 



After the larva has done sufficient " spinning," probably by mid- 

 summer (but I cannot speak with certainty as regards date), it moults, 

 leaving its first moult (Fig. 3a) at the narrow end of the covering, and slips 

 backward. More spinning is now done, but very soon it again casts its 

 moult, and again slips backward underneath the cast-off skin and under- 

 neath the spun covering. This is the final " cast," and the metamorphosis 

 is complete ; it is now a full-grown female insect. In the adult state the 

 female spins more covering, but if we examine the insect microscopically 

 we find that she is an inert, legless, slug-like object (Fig. 5). The sole object 

 is now to lay her eggs, and suck the juices of the plant by means of the 

 long rostrum which is inserted into the bark. The rostrum and setae fulfil 

 the twofold object of mouth and anchor. The female commences depositing 

 her eggs in September, and dies soon after performing this function. 

 At the time she commences depositing her eggs her body fills the 

 ovisac, but as the eggs are deposited her body gradually shrivels until it 

 remains as a small "portion" at the narrow end of the covering or 

 sheath (Fig. 4). 



Let us now make a microscopical examination of the female. A little 

 practice will soon enable us to distinguish the shrivelled body of the 

 female from the eggs. If we boil this body in caustic potash and mount 

 in balsam in the usual manner, we shall observe the distinguishing 

 characteristics which form the basis of classification. First let us note 

 the well-developed rostrum, and then examine the anal segment, or 

 pygidium. The number and arrangement of the spinnerets, the anal 

 lobes, and hairs on the dorsal surface, and other characters requiring the 

 highest powers of the microscope to display, are all taken into account 

 by the specialist in this group. I have, however, refrained from entering 

 into these details, which are only interesting to the specialist. 



The male differs very materially from the female. We noticed no 

 difference existed in the larval forms, but after spinning operations a 

 difference is noticeable to the naked eye. The scale of the male (Fig. 6) 

 is lighter in colour, shows the remains of only one larval moult, and is 

 more lineal and carinated. Like the female, it slips from under the larval 

 moult, but differs from the method followed by the female, inasmuch as it at 

 once passes into the pupal form, and by the middle of July emerges a perfect 

 two-winged insect (Fig. 8), having undergone its complete metamorphosis. 

 Last season I bred out a very large number of males, several specimens 

 of which I sent to Mr. Mosley, Huddersfield, who in reply said : 

 " You could not have sent me anything I appreciate more, as I have been 



