1949] 
Q nay — P o lyplax 
181 
setae anteriorly on the ventral lobe, and one anteriorly on 
the dorsal lobe; the ventral marginal seta of the first 
plenrite is usually more than twice the length of the dorsal 
seta and may approach the length of the pleurite itself ; 
second pleurite, elongate and attenuated anteriorly, the 
ventral marginal seta exceeds the dorsal in length and is 
usually about half the length of the pleurite ; third pleu- 
rite, elongate and attenuated anteriorly, with the spiracle 
barely inclosed by the ventral margin, and with the dorsal 
marginal seta the same length as that of the second pleu- 
Figure 1. Polyplax alasTcensis. A. Female. B. Male. 
rite but longer than the ventral marginal seta of its own 
pleurite ; the spiracles of the third to seventh pleurites are 
uniformly large and are progressively more centrally 
