i] INTRODUCTION 3 



and third pairs of jaws (first and second maxillae) 

 varies considerably and will be dealt with more fully 

 later ; but in all cases the first pair takes the form of 

 well-developed mandibles adapted for biting. In that 

 portion of the stinging (aculeate) section of the 

 Order, with which we are here concerned, the an- 

 tennae (feelers) of the males have thirteeen joints, 

 while those of the females, whether "queens' or 

 "workers," have but twelve. The ants are readily 

 distinguishable from the other "stingers' 1 by the 

 presence of one or more irregular elevations ("nodes") 

 on the upper surface of the "stalk" or "waist' 1 by 

 which the hindmost portion (abdomen) of the body 

 is united to the middle region or " thorax." But it 

 is no easy matter to distinguish between a "bee' 

 and a "wasp 5 in the wide sense in which we are 

 now using these words. Structurally, two diagnostic 

 characters may be relied on, so far at any rate as 

 British species are concerned : one lies in the shape 

 of the hairs with which more or less of the body is 

 clad; in "bees' some at least of the hairs are 

 "plumose," i.e. provided with short lateral offsets 

 like those on a sparsely fluffy feather of a bird ; 

 whereas in "wasps "all the hairs are "simple," i.e. 

 destitute of offsets. The other is the widened con- 

 dition of the metatarsal joint (see fig. 17) of the hind 

 legs. Since a microscope of fairly high power is 

 required to render the shape of the hairs visible, and 



12 



