the Lariur of thr yoctnn'.. 



21 



I propose to deal only with the question as to the affinities of 

 the Geometrag and Nocture, since, in the case of these two 

 groups, materials have been accumulating for some years, 

 which, in my opinion, enable us to give a definitive answer 

 to the question of their relative positions. 



Before entering into details, I may just call attention to 

 the differences in structure between the caterpillars of the 

 Noctuae and of the Geometrae. 



,. 4-^6 7 



£^ 10 it 1Z 13 



A perfect Lepidopterous caterpillar is composed of thirteen 

 segments, counting the head as the first, and possesses 

 altogether sixteen legs, the three foremost pairs being the true 

 or thoracic legs, which correspond with the legs of the perfect 

 insect. The thoracic legs are horny, and are situated on the 

 2nd, 8rd, and 4th segments. The other legs, which are 

 fleshy, are known as the abdominal legs, prolegs, or claspers, 

 and are situated on the 7th, 8th, 9th, 10th, and 13th seg- 

 ments. The larvse of the butterflies, Sphinges and Bom- 

 byces, have the full number of legs ; the caterpillars of the 

 Geometrae, on the other hand, have, as a rule, only four 

 claspers, one pair on the lOtli and 18th segments, so that in 

 walking they arch their backs in the peculiar manner so 

 familiar to us, and which has given rise to the name of 

 "geometer" or " looper." Some few exceptions occur 

 among the Geometrae, such as Eumia Cratmjata and Odontopera 



