364 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



abdomen consists of about thirty segments. The beak, a short, curved 

 tube, is usually retracted between the organs of the mouth. The latter 

 form a truncated cone, concealed from above by the projection of the 

 front, and difficult to resolve into its component parts. Under high 

 powers it can be seen to consist of at least two thick lobes, which in the 

 liviug mite have a reciprocal forward and back movement. 



The two pairs of legs are placed close together, at or very near the 

 anterior extremity, and project forwards. They are four-jointed, and 

 terminate in a curved spine, with opposing bristles. (Plate IX, Fig. 

 5, c.) The intermediate joints bear one or two very long, curved bristles. 

 Several tine bristle-hairs, arising from the under surface of the body, 

 curve upwards at the sides, and two very long bristles at the caudal ex- 

 tremity , curving down wards, arc trailed after the mite as it crawls. 



The length of the adult mite is 0.14 mm ( T ^- o inch). The young do not 

 differ essentially in structure from the adult mites, but are thick and 

 short, almost cordiform, and the legs are very short. 



The eggs, which are deposited singly or in little clusters upon the 

 surface uf 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 increase in size by the absorption of 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. (Plate IX, Fig. 5, d.) 



Life-history. — In hot weather the eggs hatch in four or live 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 exceeds two weeks. 



The young mites are bright, translucent yellow in color. Within a 

 week or ten days they undergo a metamorphosis or molt, during which 

 the animal remains dormant for about forty-eight hours. With its legs, 

 which are placed close together, aud 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 spiudle-shaped. The 

 body of the transforming mite separates from the old skin, which be- 

 comes pellucid and empty at the extremities, and finally splits longi- 

 tudinally, releasing the renovated mite. The rejected pellicle is left 

 firmly adhering to the surface on whicu it rests, but is in time removed 

 by the action of the weather, and much sooner from the leaves than 

 from the rind of fruit. 



Tiie adult mite is slightly darker than the young in color, and be- 

 comes more opaque as it grows older. Xo sexual differences have been 

 distinguished, nor has the act of coupling been observed. 



Owing to the difficulty of confining the mites without interfering with 

 the conditions necessary to their existence, it has not been possible to 

 determine the duration of their lives. It is, however, safe to conclude 

 that they live several weeks after reaching the adult stage. The num- 

 ber of eggs deposited is also uncertain, but it is probably not abnormal, 

 and the enormous populousness of their colonies must be attributed to 

 rapid development, aud comparative immunity from enemies and para- 

 sites, rather than to excessive fecundity. 



Food. — This evidently consists of the essential oil which abounds in 

 all succulent parts of the orange and its congeners, and which the mites 

 obtain by penetrating with their sucking beaks the cells that lie im- 

 mediately beneath the epidermis. That they do not feed upon the chio- 

 rophyl, is shown by the color of their intestinal contents, which has no 



