THE RUST MITE. 115 



from the under surface of the body, curved upward at the 

 sides, and two very long bristles at the caudal extremity, 

 curving downward, are trailed after the mite as it crawls. 



The length of the adult mite is 0.14 millimeter (.005 

 inch). The young do not differ essentially in structure 

 from the adult mites, but are thick and short, almost cordi- 

 form, and the legs are very short. 



The eggs, which are deposited singly or in little clusters 

 upon the surface of the leaves, are spherical, transparent, 

 with a yellow tinge. Their diameter is more than half 

 that of the mite at its widest part, and they probably in- 

 crease in size by the absorption of the moisture after they 

 are laid, otherwise the body of the mite could not contain 

 more than three or four fully developed ova. The embryo 

 is curved within the egg, its head slightly overlapping the 

 tail. 



Life History. In hot weather the eggs hatch in four or 

 five days, but in winter their development is more or less 

 retarded by cold, although it is not entirely arrested, even 

 by frost, and the duration of the egg period seldom ex- 

 ceeds two weeks. 



The young mites are bright, translucent, yellow in 

 color. Within , week or ten days they undergo a meta- 

 morphosis or molt, during which the animal remains dor- 

 mant for about forty-eight hours. With its legs, which 

 are placed close together and stretched out in line with 

 the body, and with its two-lobed anal proleg, it clings 

 closely to the surface of the leaf. The form becomes 

 more elongate and spindle-shaped. The body of the trans- 

 forming mite separates from the old skin, which becomes 

 pellucid and empty at the extremities, and finally splits 

 longitudinally, releasing the renovated mite. The rejected 

 pellicle is left firmly adhering to the surface on which it 

 rests, but is in time removed by the action p,f the weather, 



