138 WASPS [CH. V 



conveniently placed for receiving the fluid between them. 

 The poison escapes from between the needles at their 

 apices and also through five minute canals pc (Fig. 26), 

 that pass obliquely from the poison groove through the 

 bases of the first five barbs b (Fig. 26). Neither the 

 director nor the needles are solid structures ; tracheal 

 tubes are plainly visible within their substance and dis- 

 tinct cavities are visible in transverse sections. 



Fig. 26. Optical section of tip of a needle from the sting of Vespa 

 germanica ? . Highly magnified. 



*. Barbs, p.c. Poison canals perforating bases of barbs, p.g. Poison 

 channel running along inner face of needle, cf. Fig. 25. Actual 

 length of the part figured 0'37 mm., breadth at widest part 0-05 mm. 



The poison is said by Bordas 1 to be formed by the 

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

 acid and the other alkaline. It certainly gives a strong 

 acid reaction with blue litmus paper, but we have not 

 been able to detect the alkaline constituent. 



It may perhaps be not out of place to observe that the 

 painful effect of a wasp's sting is entirely prevented by 

 the prompt application of ammonia to the wounded spot. 

 The popular idea that a wasp is always anxious to use its 

 sting is entirely wrong : so long as the insect is not inter- 

 fered with and hasty movement is avoided there is not the 

 least likelihood of the weapon being employed. It is 



1 C. R. Acad. Sci. Paris, cxvm. 1894. 



