THE PEACH BUD MITE. Ill 



i 



SYSTEMATIC RELATIONSHIPS AND OTHER ECONOMIC SPECIES. 



According to Banks l the family Tarsonemidse is a small one of 

 much biological and economic importance. There are two sub- 

 families, Pediculoidinse and Tarsoneminse. These soft-bodied mites 

 resemble also the Tyroglyphidse, though the females differ from 

 these and all other mites in the presence between the legs (pairs 1 and 

 2) of a prominent clavate organ of uncertain use. Concerning the 

 systematic position of the family there has been considerable doubt 

 among the students of the Acarina and it has not long held any one 

 position. It has been associated with the Oribatidse and the Chey- 

 letidse, and, according to Berlese, the family constitutes one of the 

 principal groups of the order. 



The subfamily Tarsoneminse includes but two genera, the species 

 differing from those of the other subfamily in that the hind leg of the 

 female ends in a long hair. The two genera, Disparipes and Tarsone- 

 mus, are represented by a considerable number of species, and many 

 species of Tarsonemus are of distinct economic importance. Tar- 

 sonemus oryzse, Targ.-Toz. infests the culms of the rice plant in Italy, 2 

 and produces the malady described by Negri under the name u bian- 

 chella" (bleaching), which is particularly characterized by the pres- 

 ence of numerous very fine threads or fibers thought to be produced 

 by this acarid; this thread-spinning habit is not found, apparently, 

 associated with any other species of the genus thus far known. 



An affection of oats in France and Germany caused by Tarsonemus 

 spirifex March, has recently been well treated by Dr. Paul Marchal 

 and others. 3 The mites inhabit the sheath surrounding the head or 

 panicle of the oat plant, preventing proper development, and causing 

 the stem to assume a distorted spiral shape, which may push out 

 along the side. In other cases the distorted stem is held inclosed in 

 the sheath, which becomes fusiform, and these plants are called 

 " avoines en cigares." The mites appear early in June and the charac- 

 teristic spirals during the second fortnight of the same month; all 

 stages, as the egg, larva, and both sexes of the adult being found 

 together on the plant. It is not known how this mite passes the 

 winter. Marchal suggests the possibility that it may hibernate in a 

 very resistant condition in the soil, though evidence to the contrary 

 is cited as obtained by M. Guille, who considers it probable that the 

 mites migrate in the fall to adjacent wild grasses. The mite also 

 lives in wheat, barley, and rye, though oats is the preferred food. 

 Excessive dry weather is regarded as favorable to its development. 



i Proc. U. S. Nat. Museum, vol. 28, p. 74, 1893. 



2 La mallatia della bianchella del riso cultivato. Casale, 1873. 



3 L'Acariose des avoines. Annales de l'lnstitut National Agronomique, 2d ser., tome 6, fasc. l er , 1907. 



