OF DIGESTION. 381 



substance, the presence of which is to be deduced from the variety of 

 their food. 



True poison glands are less generally distributed : we have de- 

 scribed them above ( 140) among the appendages of the female 

 sexual organs. They are found only in the Hymenoptera, viz. in the 

 Pompili, Spkeges, wasps and bees. The secretion of these organs is a 

 sharp corrosive fluid, which is the principal cause of the violent pain 

 that is experienced from the puncture of these insects. The form of 

 the sting, which has also been described above ( 145), enables them 

 to insert this poison into the wound at the time of the puncture, as the 

 sting is not simple, but consists of several setae, which form a narrow 

 canal. We find, likewise, in the Lepidoptera, appendages which, in 

 structure and place of opening, appear to be analogous to these poison 

 glands. This analogy is supported by the intelligence of some residents 

 at the Cape of Good Hope, who inform us that there is a lepidopterous 

 insect known there by the name of the bee-moth, which defends itself 

 in stinging when captured, and the puncture is so painful, that a large 

 swelling speedily arises which quickly produces inflammation *. The 

 chemical composition of this poisonous fluid cannot be given without 

 analysis : it perhaps contains a free acid allied to the formic acid, or is, 

 probably, the very same thing, which supposition is supported by the 

 similarity of the pain to that of a wound from an ant. These creatures, 

 namely, have no sting, but yet they possess the poison organs, and 

 project from their anus by raising their abdomen this sharp fluid against 

 their enemies. Its acuteness is shown by the violent pain caused 

 by being sprinkled with it. They also defend themselves by biting, 

 but their bite is harmless. That these organs are analogous forms 

 to the urinary organs of the Cnrabodea and Dytici, is on the one side 

 supported by their similar situation at the extremity of the body, yet 

 with this important difference, that these open above the intestinal 



* Isis. 1831, p. 1917. From a letter received by Professor Reich from the Cape of 

 Good Hope. It is the opinion of the entomologists cited there, that the projecting sting 

 is the male organ, but it is contradicted by a Brazilian Cossus in the Royal Entomological 

 Collection at Berlin, and which is a female : it has a long and very pointed sting, which 

 is recurved, but I was not at liberty to inspect it more closely. According to analogy, 

 this sting can be nothing else than an ovipositor formed by the projection of the horny 

 ridges found in the vagina of all insects. It appears most to correspond with the sting of 

 the Hymenoptera, yet it appeared to rne that the exterior sheaths were wanting, if I may 

 trust a very superficial glimpse which was all I could have of it. 



