772 
DR JOHN RENNIE ON 
species. The external genitalia consist of two rounded lobes, projecting posteriorly 
on each side of a tapering triangular penial sheath. 
Legs. — Special features regarding the limbs are : On the penultimate segment 
of the second pair of legs there is a prominent sensory organ. The fourth pair of 
legs is relatively slender, and presents the most distinctive characteristic of the 
species in this sex. There are three joints, all of which are comparatively weak ; 
the terminal one bears the very long, stout, and finely curved hair distinctive of 
the genus. Just within this, and almost at the tip of the last segment, is a small 
straight spine, which occupies the position of the incurved terminal claw, charac- 
teristic of free-living species. Close examination has suggested that this structure 
is of the same character as that on the second pair of legs of the males, and on the 
female limbs also, and that it is probably sensory in function (fig. 7). 
Larva. — The larva is large, being about ’2 mm. in length by about '08 mm. in 
width at its broadest part. The mouth parts resemble those of the later stages. 
There are three pairs of short legs ; the first terminates in a double claw (fig. 4). 
Ovum.- ! — The egg is large, being about T4 mm. long by '06 mm. broad, and 
slightly concave along one side (fig. 2). 
All the Heterostigmata appear to be parasitic, some on plants, others upon 
insects, and doubtfully on warm-blooded vertebrates. The majority of the described 
species of Tarsonemus are found upon plants ; the others are from the bodies of 
vertebrate animals, in which a number have been found associated with malignant 
growths. T. woodi, n. sp., appears to be the only species known to occur in 
insects. Its discovery as an endoparasite within the hive bee therefore constitutes 
a significant advance in our knowledge of these mites, and of the general importance 
of the genus, apart from the far-reaching suggestiveness of its causal relationship 
to a disease in hive bees which has baffied inquiry for the last sixteen years. 
As giving a more detailed indication of the habits of the genus, the following 
brief references to the best-known species are submitted. In view of the importance 
of habit and habitat in the case of T. woodi, I have preferred to refer to these, 
not in the order of their original discovery or description, but to group them 
from this point of view. 
Hall-forming Species. 
T. jloricolus On. and F., 1876. — This species is described as occurring on the 
flowers of Verbascum, forming galls in foliage of Vitis vinifera, Coryllus avellana, 
Salix alba, etc., in putrefying stuff, and in frass of bacon beetle. T. ( Cheylurus ) 
socialis, according to Berlese, is of the same species. It is described from the skin 
and base of the feathers of birds of very diverse species, both terrestrial and aquatic. 
T. buxi Canestr. and B., 1884. — Occurs as an inquiline in Phytoptus galls and in 
Diplosis galls, See Canestrini (1886), pp. 320-1, 
