114 FLORIDA FRUITS ORANGES. 



oil-cells have been emptied of their contents, or the tissues 

 have been too much hardened by advancing maturity to 

 be easily penetrated by their beaks. 



The effects of their puncture upon the cellular structure 

 of the plant, however, continue after their departure, and 

 upon the fruit rust develops with a varying interval, de- 

 pending possibly upon the relative humidity of the air. 

 Usually the discoloration is very apparent after the lapse 

 of a week, and the rind continues to harden indefinitely, 

 or as long as it is exposed to the air. 



Description. The so-called rust insect is a four-legged 

 mite, honey-yellow in color, and about three times as long 

 as broad. The body is cylindrical, widest near the ante- 

 rior extremity, and tapers behind, terminating in two 

 small lobes, which assist the animal in crawling and enable 

 it to cling firmly to the surface upon which it rests. The 

 front is prolonged in a conical protuberance, which ap- 

 pears to be composed of two closely applied lobes. The 

 upper surface at its widest part is marked on each side 

 with shallow depressions, which are faintly prolonged on 

 the sides and reach nearly to the terminal lobes. The ab- 

 domen 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 living mite have a reciprocal forward and back move- 

 ment. 



The two pairs of legs are placed close -together, at or 

 very near the anterior extremity and project forward. 

 They are four-jointed, and terminate in a curved spine, 

 with opposing bristles. The intermediate joints bear one 

 or two very long bristles. Several fine bristle hairs arising 



