TRACHEATA 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 lke 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 Fic. 198.—Silk-worm moth, Bombyx mori. 
the Tineidae, where they are A. Female. B. Male. 
well developed. 
The second maxillae or Jabium 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 all fused together, the wings are 
large, and the © rior 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 
