THE WOOLLY WHTTE-FLY. 



67 



si 



o° o Oo 

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Unless molested or crowded each female deposits her eggs in a com- 

 plete circle (PL IV, fig. 2), she being always on the inside (fig. 19, c). 

 This arrangement she effects by using her mouth parts as a pivot 

 upon which to rotate her body. Since often as many as 3 or 

 4 rows of eggs are present in one circle, it is evident that the female 

 describes several circles while ovipositing before seeking a new place. 

 Although as few as 27 v^s have been counted in a single circle and 

 as many as 130 in a circle of 4 rows, it is probable that the larger 

 number does not indicate the maximum egg-laying capacity, which, 

 in the case of A. c/tri, has been found to be 222. 



The eggs are whitish when deposited but soon turn to a dark-brown 

 or blackish color and become partially covered by waxen secretions 

 rubbed from the bodies of the adults. They are curved, the concave 

 side being upward (fig. 19, a, b), and in hatching the membranes 

 rupture along the median distal half of the upper surface and do not 

 spring back into place after 

 the larva has escaped. 



The larva after hatching 

 crawls about before settling. 

 It is yellowish, elliptical, with 

 9 pairs of marginal spines and 

 4 pairs of short, stout, dorsal 

 spines. Soon after ceasing 

 to crawl, it develops a short, 

 inconspicuous, marginal wax 

 fringe similar to that of the 

 first ins tar of A. nubifi ra (fig. 

 20). In the second instar 

 the marginal bristles are lost 

 except one anterior and two posterior pairs, and the legs become 

 unfit for locomotion as is the case with other aleyrodids. During 

 thi- instar there develop 6 white abdominal cross-bands and a 

 distinct, white, marginal fringe of wax, varying in width with age, 

 often becoming 0.3 mm. wide; aside from these Becretions, each of 

 the dorsal spines secretes a long, outstanding waxen rod. o( varying 

 length, these rods being at all times characteristic of this instar 

 lig. 21 ). After passing into the third instar the larva, except in 

 point of size, assumes the appearance of the pupa: the marginal 

 fringe and abdominal secretions found in the preceding instar remain 

 practically the same, but these are largely or wholly concealed by 

 the long, white, curling, and variously matted secretions which arise 

 from along, but not on, the margin of the insect, giving to a leaf 

 infested with this species a woolly appearance {V\. IV, fig. \) which, 

 when infestation i- heavy, entirely conceals the insect beneath. These 

 threadlike secretions are often twice as long as the insect itself. At 



o o o ^ c 



Fig. 19.— The woolly white-fly (Aleyrodes howardi): a, 

 Egg, showing attachment to leaf; b, eggshell, viewed 

 from above; c, female depositing eggs in a circle, c. Much 

 enlarged; a.b. highly magnified. (Original.) 



