DESCRIPTIONS OF GENERA AND SPECIES. 257 



FEMALE. 



Shape. Ceplialotliorax a very short wide triangle, 

 abdomen almost square; the two are distinctly divided 

 by a transverse line. 



The Plumose Hairs (PL XI, figs. 17 and 23). These 

 are by far the most striking feature of the species, and 

 therefore I describe them first and separately. The 

 body is bordered by thirteen bilateral pairs of large 

 and elegant plume-like hairs ; these do not vary 

 greatly, but those at the sides of the body are rather 

 the longest and most curved, the first pair being nearly 

 straight, except for a downward curve, which is slight. 

 Those on the posterior margin are rather smaller, and 

 diminish more rapidly from base to apex than the 

 others ; they are therefore not quite so graceful. Five 

 pairs are on the cephalothorax, and eight on the 

 abdomen. There are also five pairs of almost similar 

 hairs on the notogaster, arranged as follows, viz. one 

 rather small pair near together, about in a line with 

 the fifth pair of peripheral hairs, or between them and 

 the fourth ; one pair considerably longer, but even 

 nearer together, about in a line with the seventh 

 peripheral pair ; one long, but much less plumose pair 

 about in a line with the ninth peripheral pair, but 

 further apart ; and two rather smaller pairs in a trans- 

 verse line a little further back ; these last-named three 

 pairs of hairs form rather a bunch. Adopting, as conve- 

 nient, the nomenclature of a bird's feather, each plumose 

 hair consists of a central shaft or rachis, generally more 

 or less curved. This rachis has a number of very minute 

 roughnesses or projections arranged linearly, and it also 

 has a projection at the insertion of each barb. The 

 vexillum of the feather consists of about fourteen to 

 twenty parallel barbs on each side of the rachis ; 

 the barbs on the two sides of the rachis are sometimes 

 opposite, sometimes not. The barbs are mostly of 

 some approach to equal length until near the tip of 

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