238 



ANNUAL. REPORT OF THE 



Off. Doc. 



bat thej remain so for a few days only. Additional waxy material 

 is added at the edges, the scale enlarges, becomes darker iu color, 

 more flattened, and reaches the gray stage. From ibis the color 

 changes to black and later, as it becomes mature, it again lightens 

 and the yellow centre becomes obvious. In about four weeks full 

 growth is attained and the female is sexually mature. Jf we follow 

 the insect beneath the scale, we find that as the covering increases, 

 the antennae and legs disappear and, when the first larval skin is 

 cast, no appendages remain. The cast skin is made to form part of 

 the centre or nipple of the scale, and in the female, a second cast is 

 added before the insect is sexually mature. The male at its next 

 change differs totally from the female and forms a true pupa, from 

 which we get in a few days, a very minute, frail, two-winged fly with 

 long stout feelers, long legs and a long anal style or process. This 

 male is so small and inconspicuous that it is almost impossible to 

 see it without a magnifying glass, and so frail that the least puff of 

 wind carries it off; nevertheless, it succeeds in impregnating the fe- 

 male and then dies. 



Pig. 3. — Adult male, Aspidintiis pernioiuHun: greatly enlarged. 

 {From Hoiwi/d, Circ. ,3, 2d so:, DLv. Eat., U. S. Dept. Agr.) 



Breeding begins in the latitude of Philadelphia about June 10, 

 and continues throughout November in ordinary seasons. During 

 that time a single pair may, if absolutely unchecked, produce a 

 progeny of over one thousand million (1,000,000,000)! This number 

 is so enormous as to be almost incredible; but from the facts given 

 it may be easily figured out by any one with a mathematical turn of 

 mind. 



It has been stated that breeding continues until very late in the 

 fall, but those insects that start late never live over until the fol- 



