186 Prof. E. K. Brandt on the Anatomy of 



. The anatomy of the Clear-wings is particularly interesting, 

 because these moths exhibit obvious mimicry. The most 

 remarkable point about the anatomy of S. scoliaiformis is that 

 this mimicry does not originate in the perfect state, but 

 exhibits a partial arrest of development at the normal con- 

 dition of the pupa-state. The imperfect scaling of the wings 

 may be thus explained ; for the scales of Lepidoptera are 

 developed gradually during the formation of the pupa. A 

 similar arrest of development at some stage in the formation 

 of the pupa is likewise visible in the internal structure. This 

 shows that the Clear-wings are probably ancient forms which 

 have latterly acquired a special adaptation to (or mimicry of) 

 other flower-frequenting insects. 



The present paper includes my observations on the dissec- 

 tion of three specimens (one male and two females) of Sesia 

 tipuliformis and two specimens (male and female) of TrochiUum 

 apiforme. 



Sesia tipuliformis. 



The skeleton exhibits the same peculiarities which I had 

 already noted in S. scolueformis. It deserves special atten- 

 tion that there are three distinct thoracic segments in these 

 Clear-wings. 



As regards the mouth-organs, the proboscis is moderately 

 developed but very weakly constructed. 



The nervous system is composed of nine ganglia, viz. two 

 cephalic (supra- and infra-oesophageal) , three thoracic, and 

 four abdominal. The supra-oesophageal ganglion is well 

 developed and exhibits considerable and well-marked sinuo- 

 sities ; the visual parts are broad, thick, and short. The 

 infra-oesophageal ganglion is small and placed very near to 

 the supra-oesophageal. The first thoracic ganglion is placed 

 nearer to the infra-oesophageal than to the second thoracic 

 ganglion, but the second and third thoracic ganglia are very 

 near together. The abdominal ganglia are rather small and 

 placed at equal distances apart. The last thoracic ganglion 

 is larger than the rest and distributes nerves to the various 

 limbs and also to the reproductive organs and to the straight 

 intestine. The nervous system is arranged on the same prin- 

 ciple in both Sesia tipuliformis and scoliaformis, but is 

 arrested in development, for we find here three thoracic 

 ganglia, as is usually the case in the pupa, whereas only two 

 separate thoracic ganglia are usually present in the imago in 

 the typical nervous system of Lepidoptera. 



The digestive organs exhibit the following parts : — (1) the 



