67 



Also as larva' the four species are difficult to distinguish from each other; 

 the hest characteristics are the following: In O. cantans the sipho is much shorter 

 than in the other above-named species; it does not reach more than about three 

 times its own width at base; those of the others about four times. Among the other 

 three species annulipes is distinguishable by means of the pecten, the two last spines 

 not being detached from the others, and provided with lateral thorns like these. 

 The two other larva?, those of 0. lutescens and excrucians are difficult to distinguish 

 from each other; I refer to the descriptions given above. — It will be seen that 

 whereas it is difficult to distinguish 0. lutescens and excrucians as larva? from each 

 other, the difficulty is not so great with regard to the imagines; otherwise annu- 

 lipes and cantans are easily recognizable as larva 1 , whereas as imagines it is often 

 impossible to recognize them. 



8. O. detritus (Haliday). 

 Tab. VII. 



Description. Female. Proboscis moderate, cylindrical uniform, dark brown 

 almost black, sprinkled with white scales especially near the base. Palpi black with 

 many whitish scales and some black seta?. Antenna- filiform, the joints subequal, 

 rugose pilose, black, sprinkled with whitish scales; second joint thicker, but scarce- 

 ly longer than third, pale; tori subspherical with a cup-shaped excavation, lute- 

 ous, darker within, outwardly sprinkled with many white scales, hairs of whirls 

 black. Clypeus rounded prominent, black, nude. Eyes black. Occiput black, covered 

 with lanceolate, curved, creamy scales; on the sides broader; generally an ill-defined 

 lateral black spot; bristles on the occiput and along margin of eyes black, those 

 between the eyes yellow. 



Prothoracic lobes elliptical, remote dorsally, black, clothed with narrow white 

 scales and dark bristles. Mesonotum black with a monotonous coating of yellowish 

 brown or reddish hairs, without distinct brighter or darker lines; scutellum trilo- 

 bate, black, each lobe with a group of bright bristles. Postnotum elliptical, promi- 

 nent, blackish, nude; pleura; dark brown, coxa? luteous, both covered with patches 

 of elliptical, flat, white scales. 



Abdomen subcylindrical, tapering posteriorly; dorsal vestiture with broad white 

 basal bands, tending to expansion in the middle line; seventh segment almost 

 yellowish white; sprinkling of the darker parts of the abdomen with numerous 

 white scales; venter yellowish-white with a median series of three dark spots and 

 with two other more inconspicuous dark spots in each apical corner of each seg- 

 ment. Wings rather broad, hyaline, petiole of second marginal cell and second 

 posterior cell shorter than their cells; basal cross-vein distant less than its own 

 length from anterior cross-vein; scales black, but with numerous white scales scatter- 

 ed over all the veins, especially over the subcostal vein which may be almost 

 pure white. 



9 



