CH. V] WASPS 125 



unpalatable. There are however exceptions, for a con- 

 siderable number of defenceless insects mimic the black 

 and yellow uniform of the wasps and, sailing under false 

 colours, escape attack. Of our English insects which mimic 

 wasps we may mention in this category the dipterous flies 

 Chrysostomum sylvarum, Volucella inanis, V. inflata (in 

 a less degree) and Myriatropa florea\ the beetles Strangalia 

 armata, Clytus abietis, Rhagium bifasciatum, Pachyta 

 octomaculata, Necrophora ruspator, N. vespilio, Gicindela 

 sylvatica, Gallistus lunatus and others ; and the Clearwing 

 Moths of the genus Sesia. 



It may be well to point out how a wasp may be 

 known and with certainty distinguished from its mimics 

 without having recourse to the sting. Wasps, then, have 

 two pairs of transparent membranous wings; when at 

 rest they fold the anterior wings longitudinally so as to 

 diminish their breadth by one-half. Wasp-like flies have 

 only one pair of wings and these they do not fold; the 

 beetles have only the hinder wings membranous, the front 

 pair being horny and opaque ; Clearwing Moths have two 

 pairs of more or less transparent membranous wings but 

 they do not fold them when in repose. The social wasps 

 (Vespidce) may be known from their near relatives the 

 solitary wasps (Eumenidce) by the elongated longitudi- 

 nally grooved mandibles and by the bifid or toothed claws 

 of the latter: a Vespid also possesses two spurs at the 

 apex of the middle tibiae whereas an Eumenid has but one. 



In powers of locomotion wasps are, on the whole, 

 superior both to the dragonfly and cockroach. The cock- 

 roach is a swift runner but an infrequent flier, the 



