( clvii ) 



lated to it, and is projected forward into a shortish curved uncal 

 horn ; the harpagones are broadish, constricted above and 

 below medially, but expanding again widely at the apex, 

 the front line of the apex being slightly hollowed between its 

 upper and lower extremities — there is a peculiar triangular 

 ventral plate that is deeply hollowed, tapering off to a pointed 

 extremity; the sedoeagus is long and very narrow, being an 

 almost simple tube, the vesica having but a slight armature. 



The Geometrinae are on the whole simpler and more ad- 

 vanced in structure than the two previous subfamilies, but 

 space impels certain limits, so that I must content myself 

 with a single example, the structure, however, varies in almost 

 every genus. 



Tolmera albihasalis. 



The cingula is a simple continuous collar with a smallish 

 horn-like tegumen, from two-thirds up the girdle ; in the tergite 

 area two lateral arms arise, one on each side, to well above 

 the tegumen, that terminate in lozenge-shaped elliptical 

 apices densely shagreened, from which arise long thick 

 brushes of hair ; the harpagones are very long, quite un- 

 usually so, they are irregularly scimitar -shaped processes ; 

 the sedoeagus is shortish, broad, with the vesica slightly 

 shagreened and furnished with a formidable horn. 



The sexual armature of the Diptera is being used generally 

 by the present-day systematists. In a highly specialised order 

 such as this, we should look for well-developed clasping 

 organs. The general method of mating is as in the Coleoptera, 

 with the male on the top of the female, but the highly nervous 

 and extremely active habit of the insects would lead observers 

 to expect a difference in the development of the armature, and 

 this is the case. The clasping organs are generally very 

 complicated and very effective, and for this it became neces- 

 sary for the armature — the male being above its mate — to be 

 enabled to be curved round into a position almost vertically 

 below its own abdomen ; this is partly provided for in the 

 shape of the various organs, but mostly by a fine pliable 

 extension of chitinous membrane between the terminal ab- 

 dominal segment and the armature ; this membrane is so fine 



