THE WOOLLY WHTTE-FLY. 



69 



The larva, first instar. — Size about 0.26 mm. by 0.13 mm. ; elliptical, yellowish-white, 

 with 9 pairs of short marginal bristles, arranged as in figure 20, the two posterior pairs 

 longest, the relative lengths being as follows: 



Pair 1 2 34 5 6789 



Relative lengths 2 2.5 6 4 5 5 4 8 8 



After settling, an inconspicuous, transparent, marginal wax fringe develops, but 

 little exceeding in width the length of the marginal spines. Eyes reddish-brown, usual. 

 Dorsum with 4 pairs of short stout spines; 1 pair cephalad and mesad of eyes, 1 pair 

 at vasiform orifice, and 2 pairs on central region between the fifth and sixth, and sixth 

 and seventh pairs of marginal spines, respectively. Legs and antennae well devel- 

 oped, usual; vasiform orifice similar in shape to that of pupa, but without apparent 

 strong setse. 



The larva, second instar. — Size, about 0.38 mm. by 0.22 mm. All marginal bristles 

 lost except 2 pairs of minute bristles, one at anterior, the other at posterior end of body. 

 Four pairs of bristles on dorsum located as in first instar, but different in that when 

 wax secretions are removed, the first 3 anterior 

 pairs are stout spindle-shaped (fig. 21, a), the 

 fourth pair at vasi form orifice, long and slender, as 

 in pupal stage; a fifth dorsal pair at caudal end of 

 body but not on margin, similar to those in pupal 

 stage. Color, brownish or black; margin with 

 narrow white wax fringe, equaling at times 

 0.3 mm. Instar conspicuous because of long 

 single, stout, outstanding waxen rods secreted 

 by each of the spindle-shaped dorsal spines, 

 and 6 abdominal cross bands of white waxen 

 secretions. Insects well advanced in this instar, 

 after the dorsal waxen rods have developed, pre- 

 sent a profile similar to that shown in figure 21, 

 at b. 



The larva, third instar. — Size, about 0.58 mm. 

 by 0.38 mm. Except in point of size, this re- 

 sembles the pupal instar in all respects. The 

 spindle-shaped spines of the previous instar are 

 replaced by ordinary strong bristles. 



The pupa. — Size, about 0.9 by 0.55 mm., sub- 

 elliptical in shape. Many specimens with more 

 or less evident indentures on cephalo-lateral 

 margin of case, with cephalic end obtusely pointed. Color, on leaf, under hand 

 lens, with secretions removed, yellowish-brown varying to blackish; under transmitted 

 light, yellowish to brownish-yellow. There is a distinct marginal rim all around. 

 with wax Inbes distinct, the incision- acute and tubes rounded distally. From 

 margin of case all around arises a short rim of wax, composed oi Individual wax- 

 threads, serrated on margin as seen under a high-power microscope. Pupa usually 

 quite covered by a very copious secretion o( whitish, curling wax-rods which is 

 very conspicuous in badly Infested Leaves, quite hiding the insects beneath ( Plate 1 \ . 

 fig. 3); these waxen filaments often much greater in length than the insect's body, 

 spreading outward when insects are not crowded, but upward when crowded; and 

 arising from along the outer portion of the case, bul qo1 on the margin Itself from 

 which the above-mentioned distinct waxen fringe arises. Dorsum oi pupae with 

 many wax-secreting pores; the secretions very short, irregular upon the cephalothoracic 

 region, and on the abdominal portion arranged in cross bands on each segment, being 



b 



Fig. 21.— The woolly white-fly, second 

 larval instar. a. Spindle-shaped spine; b. 

 diagrammatic profile, showing character- 

 istic wax secretions. Highly magnified. 

 (Original.) 



