XIV INSECTA 207 



abdomen varies and in any special case is often difficult to 

 determine exactly, for the last one or two segments are often 

 much modified and sometimes withdrawn within the other 

 segments. The most usual number is ten. 



The first segment, or segments, of the abdomen may 

 be very narrow, and form a kind of waist, as is seen very 

 markedly in ants, where three segments may be thus modified, 

 connecting the thorax with the much-swollen hind part of 

 the abdomen. 



The legs of insects usually have a constant 

 Structoe. iii^bsr of joints with five distinct segments. 

 Next the body comes a short segment, the " coxa" 

 then another short piece, the ^ 

 " trochanter" next the long 



'■'■Jemur" and the "tibia," tlie ^'Mlk "n^I^I^^^^^'"'*' 

 two longest segments of the 

 leg, and finally the part known 

 as the foot or "tarsus," which j^ochanter 

 is itself formed of from one to Ir J*'"i''S 



five segments, five being the most 

 frequent number. The last seg- 

 ment bears a pair of curved claws, j,j^_ igS.-The front leg of a Bee. 

 and may also bear, between 



the claws, a lobe modified for a special purpose (see p. 330). 

 Mouth- The mouth is always overhung by an "upper 



parts of lip " or labrum, which is an overhanging flap of the 

 Insects, chitinous covering of the head. Below the labrum 

 is a pair of unjointed, hard, biting jaws, known as the 

 " hard jaws " or mandibles. These vary greatly in size in the 

 different orders of insects, reaching a maximum development 

 in the male stag beetle, where they are as long as the whole 

 of the rest of the body. Below the mandibles is a pair of 

 complex "soft jaws," or first maxillae, jointed structures with 

 several branches, the most conspicuous of which lies on the 

 outer side, and is known as the maxillary palp (Fig. 139). 

 This sometimes bears a special sense-organ at its apex, as 

 in the case of the Large White Butterfly. The other 

 lobes of the maxillae serve the purpose of holding the food 

 whilst it is being eaten. One other pair of appendages, the 

 second maxillae, seems to be represented in the head, but 

 fused together to form the median structure known as the 



