386 LEPIDOPTERA 



CHAP. 



from the tightness with which it is grasped by the cocoon, it 

 traverses over and over again " the same part of the cocoon till 

 it is cut through ; at the same time the spines act as guides to 

 a fluid which is emitted so as to soften the part that has to he 

 sundered. 



Though many other larvae of Notodontidae are of most 

 curious form and assume remarkable attitudes, yet this is not 

 the case with all, and some are quite ordinary and like the cater- 

 pillars of common Noctuidae. This is the case with the species 

 Rhegmatopliila alpina we have selected to illustrate the meta- 

 morphosis of the Order (Fig. 157). Those who wish to form an 

 idea of the variety of larval forms in this family will do well 

 to refer to Packard's beautiful volume on the North American 

 forms. 1 The family has a very wide distribution, but is absent 

 from New Zealand and Polynesia, and appears to be but poorly 

 represented in Australia. In Britain we have about two dozen 

 species. 



Fam. 12. Cymatophoridae. A small family of nocturnal 

 iiioths that connect the Bombyces with the Noctuids ; they are 

 usually associated with the latter, but are widely separated in 

 Hampson's arrangement because of a slight difference of nervura- 

 tion, nervule 5 being nearer to 6 than to 4, whereas in Noctuidae 

 the reverse is the case. The Insects, however, in certain respects 

 approach the Notodontidae, and are of interest if only as showing 

 that the linear sequences w T e adopt in books are necessarily con- 

 ventional, and to some extent deceptive. We have three genera 

 in Britain ; our pretty Peach-blossom, Thyatira batis, and the very 

 different Buff-arches, T. derasa, being among them. Meyrick 

 denies any connexion of this group with Noctuidae, and in his 

 nomenclature Cymatophora becomes Polyploca, and the family, 

 consequently, Polyplocidae. 



Fam. 13. Sesiidae or Aegeriidae (Clear-wings}. A family 

 of comparatively small extent ; its members have frequently one 

 or both pairs of wings in large part free from scales, the tip of 

 the body tufted, the hind legs of one sex peculiar. The size is 

 usually small, but in the largest forms the measurement may be 

 but little less than two inches across the expanded wings. 

 The pupa is of the kind classed as " incompletae " by Chapman, 

 the appendages not being firmly glued to the body, and much 

 1 Mem. Ac. Washington, vii. 1895, 290 pp., 49 plates. 



