INSECTS EMPLOYED IN MEDICINE, OR AS FOOD. 105 



Thomas Gage spoke of this peculiar insect pro- 

 duct as early as 1625. 



The insects whose eggs are taken to produce this 

 Mexican flour are of three species. Two of these 

 belong to the genus Corixu of Geoffrey ; the first 

 was described in 1831, by Thomas Say, under the 

 name of Corixa mercenaries ; the other is looked upon 

 as new, and has been called C.femorata. But on 

 the same reeds are observed the eggs of a third 

 insect, a new species of boat-fly, which M. Guerin 

 Menneville has termed Notonecta unifasciata ; this is 

 a larger insect. 



We have heard of a beetle called Chlcenius sapo- 

 naris (or Carabus saponarius of Olivier), of which 

 soap is made in some parts of Africa. This fact is 

 easily accounted for by the great abundance of this 

 insect and the quantity of grease it contains. 



Another beetle, Calandra granaria, a dark-brown 

 insect, with a spotted thorax, too well known by the 

 ravages it commits in the granaries of southern 

 Europe, contains both tannic and gallic acid : an ex- 

 tremely interesting fact, discovered by Mitonart and 

 Bonastre, and confirmed by the further researches of 

 Bonastre and Henry. Tannic acid and gallic acid can 

 be extracted from this beetle by means of ether, 

 alcohol, or water. The solution precipitates gelatine 

 and forms ink with salts of iron, etc., characteristic 

 properties of the substances in question. 



