STATES OF INSECTS. 305 



In the Diptera, Aptera, Arachnida, &c, I am not aware 

 of any striking difference in the colours of the sexes. 



ii. The sexes of insects vary (but more rarely than in 

 colour) in their sculpture also, and pubescence. Thus the 

 elytra of the females of many of the larger water-beetles 

 (Dytiscus) are deeply furrowed, while those of the males 

 are quite smooth and level a . The thorax of the female 

 in several species of Colymbetes of the same tribe, as 

 C. Hybneri and transversalis, on each side has several 

 tortuous impressed lines or scratches, like net-work, 

 which are not to be discovered in the male. Hyphydrus 

 gibbus Latr., which differs solely from H. ovalis {JDytis- 

 cus ovalis Illig.) in being thickly covered with minute 

 impressed puncta, is, from the observation of the Rev. 

 R. Sheppard, the other sex of this last, with which he 

 has taken it coupled ; and it is by no means improbable 

 that Hydroporus picipes {Dytiscus punctatus Marsh.) and 

 H. lineatus, — between which, as Gyllenhal has justly ob- 

 served, the same difference only exists, — are in like man- 

 ner sexual varieties. With respect to pubescence, I have 

 not much to say. Another aquatic beetle, Acilius sulcatus 

 Leach, has not only its elytra sulcated, but the furrows 

 of these, and a transverse one of the thorax, are thickly 

 set with hair; while the male is smooth, and quite naked. 

 Particular care seems to have been taken by the Creator, 

 that when all the above inhabitants of the water are paired, 

 the male should be able to fix himself so firmly, by means 



a A remarkable anomalous exception to this rule sometimes oc- 

 curs in the female of D. margbialis, which has smooth elytra like the 

 male (Gyll. Ins. Suec. i. 467 — )• I have this variety from the Rev. 

 Mr. Dalton, of Copgrove, Yorkshire. 



VOL. III. X 



