DESCRIPTIONS OF SCALE AND INSECT. 51 



however, examination of the trees under observation always shows 

 many migrating ^^oung- which must have been born during the night, 

 while observations at nightfall show always as many, and frequently 

 more, which have been born during the day. 



The gradual production of the young by the female has an important 

 bearing on the question of remedies, and the old washes, which aimed 

 at the destruction of the young as soon as they emerge from the females, 

 are rendered almost valueless because, to make them effective, it is 

 necessary to repeat them many times during a period of six weeks. 

 Within two or three days after hatching the young larva? will have 

 formed a scale which will be impervious to these weaker washes. 



The larva does not ordinarily travel far from the parent insect, and 

 usually rests within a few inches of the old scale or at the first avail- 

 able point. They will not, so far as observed, travel very far from 

 the base of the tree, and in the potted trees none were observed to go 

 more than 2 inches from the base of the trunk. 



DESCRIPTIONS OF SCALE AND INSECT. 



Scale of female. — The scale of the female is circular, very slightly 

 raised centrally, and varies in diameter from 1 to 2°'°', averaging about 

 1.4™™. The exuvia is central ornearl}^ so. The large, well-developed 

 scales are gray, excepting the central part covering the exuvia, wdiich 

 varies from pale to reddish yellow, altho in some cases dark colored. 

 The scale is usually smooth exteriorly or sometimes slightly annulated, 

 and the limits of the larval scale are always plainly marked. The 

 natural color of the scale is frequentl}^ obscured by the presence of 

 the soot}" fungus {Fumago salicina). 



Scale of male. — The mature male scale is oblong-oval, nearly twice as 

 long as wide, and averaging in length about half the diameter of the 

 female scale. The position of the larval scale is marked by a nipple- 

 like prominence located between the center and the anterior margin 

 of the scale. The scale of the male is usually darker than that of the 

 female, sometimes black, but often gray, the larval scale covering the 

 exuvia very frequently light yellow, as with the female. Not uncom- 

 monly the circular scale, formed prior to the first molt, is black, while 

 the later additions, giving it its oblong shape, are gra3^ 



The scale covering of the hibernating insects in winter is black, and 

 on the bark in summer also the scple covering is dark or often black- 

 ened by the soot}" fungus referred to. But the normal color of the 

 scale of both female and male is light, and on the leaves of pear, for 

 example, the male scales are often a very light buff, and present such 

 a marked contrast to the winter appearance that no one would suspect 

 them of belonging to the same insect. 



Egg. — The q^o^ is never (or rarely) extruded as such by the female, 

 and as it exists within the body of the mother is a mere amniotic mem- 



