48 BRITISH TYROGLYPHID^. 



as long as the body, as is the case with the long hair 

 which terminates each fourth leg of the hypopial 

 nymph of Trichotarsus xylocopx. 



The pectinated hairs, i. e. those having pectinations 

 on one side only, are rare ; probably the best examples 

 are the hairs on the tibiae of the two anterior pairs of 

 legs of Glycyphagus ornatus Kramer, a foreign species ; 

 but it is rather doubtful whether they should not be 

 regarded rather as scales than as hairs. Other good 

 instances are a hair on the first leg of the female and 

 one on the third leg of the male of (jrlycyphagus Crameri 

 (PL XVI, fig. 12, and PL XVII, fig. 10). 



The bipectinated hairs, i. e. those with pectinations 

 on two opposite sides of the main rachis, are on the 

 contrary extremely common and may assume great 

 size and importance. Those on the notogaster of 

 Glycyphagus plumiger (Plate IX) and G. Canestrinii 

 (PL X) are the best examples. Those of the latter 

 species are particularly beautiful, the main rachis and 

 the pectinations being curved, and each pectination 

 bending suddenly forward near its distal end so that 

 the whole hair assumes an ostrich-plume appearance 

 which is very striking. In the species which have the 

 pectinations, or barbs, on more than two sides of the 

 rachis those barbs are usually extremely short and 

 fine ; although the whole hair may be nearly twice as 

 long as the body of the Acarus, as is the case in the 

 notogastral hairs of Glycyphagus spinipes (PL VII) ; 

 but a few cases exist where the barbs are long and 

 very flexible, and sometimes provided with secondary 

 barbules giving the whole hair somewhat the appear- 

 ance of down ; such hairs are generally very small ; 

 a very good example is a minute hair on the side of 

 the body of the male of Glycyphagus platygaster 

 (PL XVII, fig. 4). 



Of the rod-like hairs some of the best examples are 

 those on the notogaster of Tyroglyphus Wasmanni, 

 these slightly increase in thickness toward the distal 

 end; a short rod of a similar character is also found 



