TYPE TRACHEATA. 517 



of the Cabbage ; many other similar examples might be 

 given. A few of the Microlepicloptera possess aquatic larvae, 

 but they form exceptions. In the typical caterpillar there 

 are, in addition to the three pairs of thoracic legs, five pairs of 

 short stout prop-legs situated upon the third, fourth, fifth, 

 sixth, and tenth abdominal segments, and the body may be 

 covered with hairs of various lengths, as in the larvae of many 

 moths (e.g. the Woolly Bear, Spilosoma), or may possess 

 spiny processes, as in the larvae of the Mourning-cloak Butter- 

 fly ( Vanessa) -which feeds on the "Willow, or variously- 

 shaped tubercles, as in the American silkworm (Telea) and 

 the Cecropia larva. In one group of moths, the Geometridre, 

 but two or three pairs of prop-legs occur, situated on the 

 more posterior segments, and in progression these forms 

 draw these legs up close to the thoracic limbs, throwing the 

 intervening portion of the body into a loop, whence the terms 

 "measuring-worms" or "loopers" often applied to them. 

 In rare cases, as in a few Microlepidoptera, the larva is 

 without feet and maggotlike. 



The pupa or chrysalis is of the obteda variety, and is fre- 

 quently enclosed within a silken case termed the cocoon, 

 spun by the larva whose salivary glands are converted into 

 spinning-glands. A cocoon is more generally present in the 

 Moths than in the Butterflies, whose chrysalids are suspended 

 by a patch of silk to which the hind end of the pupa is at- 

 tached or may be in addition slung in a silken loop passing 

 round the body near the middle (Fig. 231). 



14. Order Hymenoptera. 



The Hvmenoptera possess four membranous wings, with 

 comparatively few veins and not covered with scales or hairs 

 but transparent, the anterior pair being usually larger than 

 the posterior. The abdomen is sometimes broadly attached 

 to the thorax, as in the Saw-flies (Tenthredinidae), but more 

 usually the anterior one (Bees) or two (Ants) abdominal seg- 

 ments are very narrow, so that the abdomen seems to be at- 

 tached by a stalk. The females possess ovipositors which 

 may be retractile and provided with a poison-gland, forming 



