LEPIDOPTRRA. 



[41 



only four, one pair being situated on the last ring, and the other on 

 the ninth, as in the case of looper caterpillars. And, lastly, there are 

 others which have only two pro-legs. 



The various forms, numbers, and positions of these organs, 

 produce great differences in the mode of locomotion of caterpillars. 

 Those provided with ten or eight membranous legs have in walking 

 only a very slight undulating motion. Their bodies are parallel 

 to the plane which supports them. They can walk very quickly; 

 but their steps are short and quickly repeated. Others, on the 

 contrary, in proportion as the number of their false legs diminishes, 

 and the spaces between the legs increase, walk in a more irregular 

 and quaint manner. 



If the reader will glance at Fig. 97, taken from Re'aumur's 

 " Memoire sur les Chenilles en 

 ge'neral,"* which represents a 

 looper caterpillar, with four 

 membranous legs, he will see 

 that there is a considerable 

 space between the posterior 

 legs and the first pair of pro- 

 legs, along which the body has 

 no points of support. If one of 

 these caterpillars, lying quiet and at full length, determines to walk, 

 in order to take its first step (Fig. 98) it begins by humping its back, 

 curving into an arch that part which has no legs, and finishes by 

 assuming the position seen in Fig. 99. In the former position it has 



Fig. 97. — Looper Caterpillar. 



Fig. 98.— Caterpillar curved into an arch. 



Fig. 99. Caterpillar at full length. 



its two intermediate legs against the posterior legs, and, in con- 

 sequence, it has brought forward the hinder part of its body, a distance 

 equal to the interval of the five segments which separate them. 

 There it hooks on by its intermediate and hind legs. Then it has 

 only to raise and straighten the five rings which had formed the loop, 

 ' and to advance its head to a distance equal to the length of five 



* Tome i., p. 49, Plate I., Fig. 6. 



