348 



parts. No circulatory system has been demonstrated in the 

 beetle-mites although some Acarina have a pulsating organ 

 called the heart. 



The reproductive system occupies a large part of the lat- 

 eral and posterior portions of the abdomen. In the case of 

 the male, the organs consist of a large central gland, the testis, 

 which has two ducts, the vasa deferentia, leading from it. These 

 unite to form the ejaculatory duct, which opens through a 

 small penis. The reproductive organs of the female consist of 

 a paired or unpaired ovary, and of two large oviducts which 

 pass backwards along the sides of the abdomen to its 

 posterior end, to form there the vagina, which opens to the ex- 

 terior through a large protrusible ovipositor. The ovipositor is 

 usually trifid, and may possess a few small hairs on its distal 

 end. In specimens treated with glycerine and acetic acid, the 

 large ovipositor may often be seen in repose with its proximal 

 end against the posterior wall of the abdomen and its distal 

 end at the entrance of the genital opening. 



Life History. 



Most Oribatoidea are oviparous; some species, however, ac- 

 cording to Michael, are ovoviviparous, and a few viviparous. 

 It is believed by some that many if not all the Oribatoidea are 

 parthenogenetic. Up to the present time they have never been 

 found in copulation. 



The larvae, as in the case of most of the Acarina, have only 

 three pairs of legs, which always have tarsi with monodactyle 

 claws. 



When the larvge transform into the nymphs they have the 

 full number of legs of the adult, but in other respects are very 

 different from the mature forms. Instead of being a dull 

 brown or black color, they frequently are tinted with red, yel- 

 low, or pink, and, more marked yet, their external form may 

 be very different from that of the adult. Instead of having a 

 body almost or quite free from any integumentary projections, 

 as is generally the case in the adult, they may have large, leaf- 

 like, or sword-shaped integumentary processes. These integu- 



