On the Eggs of Corixa Mercenaries. 469 



Chitine is a glucoside C 18 H 15 N0 4 , yielding glucose and lacta- 

 mide (or some such body) by the action of mineral acids, and 

 boiling with caustic potash decomposes it easily. 



But the Editor of this journal has called my attention to 

 the fact, that Chitinous substances are known to be very in- 

 digestible, so much so, that the chitinous parts of insects are 

 frequently present in the excreta of insectivorous animals • 

 and this would tend to prove that, in spite of the large amount 

 of nitrogen yielded in the analysis, and the fact of the insect 

 flour being baked into cakes, the highly nutritious quality of 

 the latter may b e reasonably doubted. 



In our climate we have representatives of these Mexican 

 boat-flies in our genus Notonecta. Indeed, three species of 

 insects appear to contribute to the formation of the Mexican 

 flour liautle, namely Corixa mercenaria, C. femorata, and Noto- 

 necta unifasciata. The first is the most plentiful, the latter is 

 the largest of the three, and resembles our common boat-flies. 



This peculiar insect product, which serves as an aliment 

 to a large proportion of the inhabitants of Mexico, was men- 

 tioned by the English naturalist, Thomas Gage, in 1625. 



M. Virlet has assured himself that the white limestone rock 

 which is forming at the present day in the fresh water lakes 

 Texcocco and Chalco, owes its oolitic structure to the presence 

 of these eggs of the Corixa and Notonecta. I have observed 

 a very similar structure in the red hematite of Namur (Bel- 

 gium), and also in a red hematite from Illinois (North 

 America) ; but the oolitic limestones of the Jura series appear 

 to have a different origin. 



