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. scoliceformis 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 Trochilium 
apiforme . 
Sesia tipuliformis . 
The skeleton exhibits the same peculiarities which I had 
already noted in S . scoliceformis . 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 scoliceformis , 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 
