POMPILIDAE 301 



repeated movements that her outline became blurred, 

 and she reminded one of the rapid oscillations of a 

 pneumatic hammer.^ 



Perhaps Pompilidae do not use the front of the head 

 because it is less broad and flat than in Sphegidae, and 

 therefore does not form such an efficient rammer ; but 

 the difference is extremely remarkable. 



The Pompilidae are most typically aposematic insects. 

 Many are of intense blue-black with shining bluish or 

 greenish black wings, often set off by canary-yellow 

 antennae. The sting inflicts a very painful wound, but 

 they do not use it unless molested, and may be watched with 

 perfect immunity so long as they are not roughly handled. 



It is difficult to conceive a more conspicuous insect 

 than one of these fine creatures as it sails through the 

 air with its long legs hanging down. Yet according to 

 some of the American naturalists these insects are con- 

 cealed by resemblance to their surroundings. 



In that case it is difficult to explain one of the most 

 striking characteristics of these large Pompilidae, namely, 

 the extraordinarily noisy flight, which is often a loud 

 rattling or clicking noise audible before the insect is seen, 

 and reminding one of a badly made piece of clockwork. 



If a Pompilid is really concealed, what is the meaning 

 of this noise which at once directs attention to it ? 



If, on the other hand, these insects are really highly 

 conspicuous, as I think, the loud noise is merely an 

 adjunct to their aposematic colouration, and serves still 

 further to advertise their owner's unpleasantness. 



Many times have I seen my pet monkeys' attention 

 caught by the noise of one of these formidable insects 

 on the wing, and they would turn their heads to the 

 direction from which it came, and watch the Pompilid 

 when it came into sight with the most careful attention, 

 being evidently anxious to avoid it when it drew near. 



^ Batozonus fuUginosus. See Proc. Ent. Soc. Lond., 1917, p. Ix, 



