38o 



Journal of Agricultural Research 



Vol. X, No. 8 



2, B. The measurements of the larvae average 214 ^ in length and 85 ^ 

 in width. 



The male larva is practically the same in form, except it is a little 

 smaller, and one can hardly detect it as being a male until one sees the 

 developments occurring in the quiescent stage. It is, however, a little 

 more stocky; the back shields compare favorably; the posterior epimera 



are a little more enlarged ; and there 

 is not so much elastic skin present. 



QUIESCENT STAGE 



No nymphal stage was found in 

 this species and instead of a nymph 

 originating from a larva, as is the 

 case in the life history of most 

 mites, the larva transforms to a 

 quiescent stage (fig. 4), which later 

 gives rise to the adult form. The 

 quiescent stage consists of the en- 

 gorged larva, which in this stage 

 is perfectly motionless and clumsy- 

 looking. It is white in color, the 

 same as the larva, and is somewhat 

 hyalin. The writer has examined 

 a large number of the quiescent 

 forms alive and mounted in glyc- 

 erin, and when so mounted the de- 

 veloping changes are plainly seen 

 under the microscope. The addi- 

 tion of a fourth pair of legs and the 

 clavate organs which the adult will 

 possess is shown within the mem- 

 brane. The quiescent period is no 

 doubt a period devoted to the for- 

 mation of new parts, and to various physiological processes prepara- 

 tory to molting. In molting, the body moves back and forth within the 

 old skin until it splits transversely along the cephalothoracic abdominal 

 groove; then the cephalic end of the mite is slowly protruded from the 

 old skin. In this form the wrinkled and elastic condition is not present, 

 as with the engorgement of the immature larva the plates or folds in the 

 larva are forced out. Measurements on a number of female quiescent 

 forms give an average length of 242 /x and a width of 128 fx. 



THE ADULT FEMALE 



The adult female (fig. 5) has a large and broad body; the venter has 

 one transverse line near the separation of cephalothorax and abdomen. 

 The general appearance is almost hyalin, and the integument is somewhat 



Fig. 4. — Tarsonemus pallidus: Female quiescent 

 larval stage with development. Much enlarged. 

 (Original.) 



