NATURAL HISTORY SOCIETY OF GLASGOW. 235 



I must not omit to notice the remarkable numerical dispropor- 

 tion between the males and females of this species. In regard to 

 marginalis and punctulatus, so far as my experience goes, the two 

 sexes are about equally numerous. Not so with Lapponkus. 

 On the three occasions when I have met with it, the females have 

 been conspicuous by their paucity — the proportion being rather 

 more than five males to every female. I am at a loss to account 

 for this remarkable disproportion. 



One theory I would suggest is this: — The males of the genus, 

 as I have observed, are smooth, while the females have the elytra 

 sulcated, each with ten furrows. In D. Lapponicus, as noticed, 

 the elytra are beautifully streaked with yellow lines, and when 

 the creature has but recently emerged from the pupa, these mark- 

 ings are particularly distinct. I was much struck, while observ- 

 ing some of the males clinging to the bottom, by the very 

 remarkable resemblance they presented to the leaf of Potamogeton 

 natans when dead and half withered. The streaks of the elytra 

 corresponded almost exactly with the veins of the leaf. May not 

 this strange resemblance to the leaf of Potamogeton, which was the 

 only plant which attracted my notice in the tarn in Ireland, be 

 the means of preserving the males from the attacks of herons, 

 gulls, and other enemies, while the female, not having the resem 

 blance so strikingly, is without this shield, and so falls a prey 

 more easily] 



Should this explanation prove to be correct, Dytiscus Lapponicus 

 may be looked upon as an interesting exception to the ordinary 

 course of nature. The general rule is that when there is "imita- 

 tion" or "mimicry," it is the female more particularly which gets 

 the benefit of the shelter. But in the present case it is the male 

 which obtains the advantage; the other sex being left in the con- 

 dition of unprotected females. 



November 24th, 1868. 

 Mr Thomas Chapman in the chair. Messrs William Haddin 

 and James D. Dougall, jun., were elected resident members. 



SPECIMENS EXHIBITED. 



The Secretary exhibited the following birds which had been 

 obligingly forwarded by William Boyd, Esq., Greenock: — 



