I ACULEATA — STING LARVA 7 



the director that they enclose between themselves and it a space 

 that forms the channel along which the poison flows, as it is 

 carried forwards by the movement of the pistons attached to 

 tlie needles. If the needles be thrust into an object quite as 

 far as, or beyond, the point of the director much poison may be 

 introduced into a wound, as the barbs are provided with small 

 orifices placed one above the other, while if this be not the case 

 much of the liquid will flow on the outside of the object. 



According to Carlet the poison of the bee is formed by the 

 mixture of the secretions of two glands, one of which is acid and 

 the other alkaline ; it is very deadly in its effects on other 

 Insects. We shall see, however, that the Fossorial Hymenoptera, 

 which catch and sting living prey for their young, frequently 

 do not kill but only stupefy it, and Carlet states that in this group 

 the alkaline gland is absent or atrophied, so that the poison con- 

 sists only of the acid ; it is thus, he thinks, deprived of its lethal 

 power. Moreover, in the Fossoria the needles are destitute of barbs, 

 so that the sting does not remain in the wound. Bordas, however, 

 states ^ that in all the numerous Hymenoptera he has examined, 

 l)oth acid and alkaline glands exist, but exhibit considerable differ- 

 ences of form in the various groups. He gives no explanation 

 of the variety of effects of the poison of different Aculeata. 



The larvae (for figure of larva of Bombiis, see Vol. V. p. 488) 

 are, without known exception, legless grulis, of soft consistence, 

 living entirely under cover, being protected either in cells, or, 

 in the case of social Hymenoptera, in the abodes of the parents. 

 The larvae of Ants and fossorial Hymenoptera have the anterior 

 parts of the body long and narrow and abruptly flexed, so that 

 their heads hang down in a helpless manner. All the larvae of 

 Aculeates, so far as known, are remarkable from the fact that the 

 posterior part of the alimentary canal does not connect with the 

 stomach till the larval instar is more or less advanced ; hence the 

 food amongst which they live cannot be sullied by faecal matter. 

 The pupa is invariably soft, and assumes gradually the colour 

 of the perfect Insect. Almost nothing is known as to the 

 intimate details of the metamorphosis, and very little as to the 

 changes of external form. According to Packard a period inter- 

 venes between the stadium of the full-grown larva and that of 

 the pupa, in which a series of changes he speaks of as semi-pupal 



1 C. E. Ac. Paris, cxviii. 1894, p. 873. 



