TEICHOPTERA. 183 



The absence of these appendages is not an important 

 characteristic, since even among Lepidoptera, when- 

 ever the habits of the larva render certain 

 pairs useless, they are apt to disappear, and 

 even the thoracic legs, which are much 

 more essential and persistent, may also in 

 extreme cases become useless and be ob- 

 literated. The Geometridae, which do not 

 walk, but have a looping gait, and therefore 

 do not need the central pairs of prop-legs, 

 have lost all but the last two pairs of these 

 organs (see Fig. 157), and some Noctuidse, 

 which are partial loopers, have, according 

 to Packard, lost the first pair. In some /^^^^^^^^^^ V:> 

 of the Lycaenidae, according to Scudder,^ "iT^"'^ 

 the gait of the larvae is a gliding mo- 

 tion, and the prop-legs are accordingly very minute. 

 Among the smaller moths, according to Stainton, the 

 larvae of the genera which bore in leaves, like Antispila 

 and others, have no prop-legs, and even the typical 

 thoracic legs have suffered reduction, having become 

 very short and minute. These tendencies reach their 

 jiatural culmination in Phyllocnistis, the larva of which, 

 according to Clemens, has no legs at all.- 



Packard states that the thorax in the adult caddis- 

 fly is like that of the smaller moths, Microlepidoptera, 

 " the prothorax being small and collar-like ; the me- 

 tanotum formed on the lepidopterous type, as is the 

 rest of the thorax, especially the coxae and side-pieces 



1 Butterflies. Henry Holt l^ Co., New York, 1881. 

 '^ See p. 202. ^^ _— ^ 



