DIPPING AND FUMIGATION OF NURSERY STOCK 5 



able in appearance, but after the first molt they lose all resemblance to each 

 other. The females lose their eyes, legs and antennae and becorrfe almost 

 circular with indistinct segments. They resemble very much a minute flat- 

 tened, yellowish sac. Springing from beneath the body, near the center, 

 they have a set of long needle-like mouth parts with which they obtain 

 nourishment from the plant. After the first molt, the male insects change 

 in appearance also. They lose their legs and antennae but instead of losing 

 their eyes they develop large purple ones and they become elongated and 

 pyriform in shape. At this time the scale covering of the body of both 

 sexes has a decidedly grayish tint mixed to some extent with yellow. 



In about eighteen days after birth, the male changes to the pro-pupa 

 or first pupal condition and the scale covering assumes a longer shape which 

 sometimes tends to be curved. At this stage the male begins to look more 

 like an insect. Two or three terminal segments can be seen, the posterior 

 one bearing two short spines. The antennae, legs and wing pads are visi- 

 ble. The purple eyes are set close together. 



About two days later, or about twenty days from birth, the male insect 

 transforms to the true pupa. The matted skin at this time, instead of form- 

 ing a part of the scale covering as in the preceeding molt, is pushed out 

 from beneath the scale. The last or third molted skin is also pushed from 

 beneath the scale. 



The male insect becomes mature in twenty-four to twenty-six days 

 from birth and pushes out backward from beneath the scale. 



In from three to five weeks from the larva, the females molt the sec- 

 ond time. The skin splits around the edge of the body. The upper half 

 adheres to the scale covering and the lower half forms a sort of ventral 

 scale between the insect and the bark. The female insect becomes full 

 grown in from thirty to forty days from birth. 



The adult male insect appears as a very small, delicate, two-winged fly 

 about 0.6 mm. long and is capable of flying from place to place. The mature 

 female does not develop as the male does, but remains concealed beneath 

 her scale as a small, yellowish, almost circular insect about 0.8 mm. wide 

 and 1 mm. long. No eyes, legs, wings or antennae are developed. 



The scale covering of the female is almost circular and slightly raised 

 in the center. The exuvia is central or nearly so. In diameter the scale 

 varies from 1 to 2 mm. The color of the scale is gray, excepting the part 

 covering the exuvia, which is a pale or reddish yellow and the ring effects, 

 which are often noted between the center and outer edge of the scale, marks 

 the edges of the molts of the larval scale. 



The scale covering of the male is darked than that of the female and es- 

 pecially in the winter, when it is black. In shape, it is oblong-oval and 

 just about half as wide as long. It ranges from 0.5 to 1 mm. in length. 

 There is a nipple-like prominence located between the anterior margin and 

 center of the scale which marks the position of the larval scale. 



In Missouri there are four generations a year and probably five, espe- 

 cially in a favorable season. The generations overlap to a great extent. 



Owing to the smallness and the color of the scales, the insect is hard 

 to detect by the untrained eye and in many cases the writer has known the 

 lenticles, or small knots on a tree, to be mistaken for the San Jose scale. 



