I7isects Injurious to the Apple. 



169 



anteiuuc. 

 the driod 



Tlicso -I'cy, ];!rval kcuIu insects crawl from l)ciieiiUi 

 scale, and wander atiout freely (jver the tree. SiKiucr 

 or later thev lix upon some definite spot, plunge their Ion- henks 

 into the plaid,, and then commences a most remarkal.ile series nf 

 changes. 



Soon after hatehuig the larva liecoines covered with a greyish^ 

 white substance. At this time, the young scale insects may readdy 

 be seen on the trees as small whitish specks. If the larva is"destuied 

 til liccomc a female it never mo\'es again. At tirst tlie lar\'a is (|iiite 

 unprotected, but by degrees a waxy excretion exudes fr(im its sk-jn, 

 and the rudiments of a scale form over it. Then it casts its skin 

 and this cast skin also fuses with the waxy covering, ami f:irms that 

 smaller area mentioned before, seen on the front of an old scale. 

 The cast skins entering intci the forma- 

 tion of the coccid scale are the so-called 

 exuviae When the little active larva 

 monlts it loses its legs, its feelers, its 

 bristles, and S(.) becomes converted 

 into a footless, almost structureless 

 body, the adult female. We see no 

 pmpal stage as miticed in the aphis. 



Let us now see \'\'liat happens if 

 the larva is to become a, male. It 

 first settles down and, just as in the 

 female, it forms a protecting covering 

 Cdiiipiised of excretions and cast skins, 

 but lit \-ory diti'erent form from that of 

 the female. Xo^\■ this larva, instead 

 of degenerating as did the female, 

 casts its skin and enters a kind of 

 ]:iu[ial stage, called the pri.ijnipa, in 



"\\']iich \ve 1ind limbs and rudiments of Avings forming, 

 rnaturcil, tliis pupa casts its skin, and from lieneatb the scale 

 tlicre issues forth a winged insect. The male scale insect has two 

 wiii,L;s, \'ery different from the Ibur-winged aphis, the single pair 

 of Avings lia\ing but one Ituked v^ein to support them. The end 

 of the body is jiri.ihmged into a long tube. This tube is inserted by 

 the male under the female scale, and so the female is fertilised. Tlie 

 male tlien (tics. The male mussel scale may uoav and then lie found; 

 but nut a hundredth part of the females which lay eggs are e\'er 

 fertilised bv a male. They, li]<e the aphis, can produce asexually, 

 that is, v\'ithiinl the agency of ii male. 



.Mussel Sr 

 -lauds, b. t ; 



\Vhcii 



