TRACHEA TA 



349 



The Lepidoptera are a very homogeneous group, contain- 

 ing a large number of species. They are familiar to every 

 one as moths and butterflies. 



The head is large, and covered with hairs ; it bears com- 

 pound eyes, and sometimes ocelli are also present. The 

 antennae are straight, but 

 vary a great deal in their 

 details. The mouth parts have 

 undergone Very remarkable 

 modifications ; the labrum 

 and mandibles are aborted; 

 the first maxillae are each 

 elongated into a very long, 

 grooved, closely-jointed struc- 

 ture, and when this is opposed 

 to its fellow the whole forms 

 a closed tube, which, when 

 at rest, is coiled under the 

 head like a watch-spring ; in 

 many species the two halves 

 of this proboscis are held to- 

 gether by a number of minute 

 hooks. The maxillary palps 

 are rudimentary, except in 

 the Tineidae, where they are 

 well developed. 



The second maxillae or labium form the spinnerets in the 

 larva or caterpillar, but they disappear in the imago ; their 

 palps, however, persist, and are large and hairy. 



The thoracic segments are aU. fused together, the wings are 

 large, and the anterior and posterior of each side are occasion- 

 ally hooked together. In some of the Geometridae the wings 

 are aborted in the females. The scales which give the beautiful 

 colour to the wings are morphologically hairs, which are flattened 

 out, and variously marked. The legs are weak, the tarsus five- 

 jointed. The abdomen has ten segments, some of them con- 

 cealed, it is covered with hairs. 



The internal organs show the following modifications. There 

 are only two thoracic ganglia. The two anterior abdominal 



Fig. 198. — Silk-worm moth, Bombyx mori. 

 A. Female. B. Male. 



