182 THE BOOK OF NATURE STUDY 



escape notice : the function of the palps is uncertain. Rolled 

 up beneath the head is the long and delicate proboscis, which is 

 capable of being unfurled and used as a tube for sucking nectar 

 from flowers. This structure is part of the first maxillae there 

 is no trace of mandibles ; but to which part of the maxillae of 

 simpler insects, e.g. wasps, it corresponds is a matter of dispute. 

 It is, however, noteworthy that the proboscis is composed of two 

 half -tubes, placed hollow to hollow, separable for undergoing 

 cleansing, but capable of close opposition when desired for suck- 

 ing ; and further, that the galece (the outer of the two pieces in 

 which the maxillae terminate) of simpler insects possess a long 

 slot upon the inner face, i.e. they are short half -tubes. It is 

 therefore not unreasonable to hold that the proboscis represents 

 a much elongated pair of galece, the view held by some ento- 

 mologists. 



Thorax. Of the three segments of the closely compacted 

 thorax the middle one is the largest. The details of the structure 

 of the thoracic skeleton are too complex for treatment here, and 

 the features are difficult to determine, in consequence of the 

 presence of an abundant covering of black hairs. The three 

 pairs of legs belong one pair to each segment. They are all 

 ordinary walking or clinging legs, with two claws at their tips. 

 In some butterflies, e.g. the peacock, tortoise-shell, and other 

 vanessids, white admiral, purple emperor, all fritillaries, the 

 meadow browns and their allies, the first pair of legs are 

 reduced in length, have no claws, and are apparently employed 

 as sense organs. The tibiae of the first and second pair have 

 articulated spurs on their middle as well as at the end ; from the 

 third pair these middle spurs are absent, the skippers being the 

 only British butterflies in which they are here present. The two 

 pairs of wings are attached respectively to the second and third 

 segments. When fully spread their expanse from tip to tip is 

 about 2j inches. The front wings are rather longer, narrow, 

 and less round at their angles than the hind, and the former 

 overlap the latter to some extent, so that in flight the two wings 

 of one side are pressed together as they strike the air, and beat 

 as though united into one. In both sexes the general colour of 

 the upper side of the wing is white, the colour being due to the 



