Sesia tipuliformis and Trochilium apiforme, Linn . 187 
oesophagus, (2) the crop, (3) the stomach, (4) the intestine. 
The last is distinctly divided into the small and large intes- 
tine, and is furnished with a blind branch (the caecum). The 
oesophagus is a very long and narrow tube, which is gradually 
dilated at the lower end, and thus forms a large sac-like crop, 
opening into the oesophagus at the wide part. The stomach 
is of an oval shape, very narrow at each end. The small 
intestine is much more slender and does not form any expan- 
sions. At the commencement of the intestine appears a pear- 
shaped branch, which is the blind intestine (caecum). 
With regard to the morphological importance of the diges- 
tive apparatus, I think it possible that it represents about 
half the usual development in typical Lepidoptera. But the 
peculiar structure of the crop indicates an arrest of develop- 
ment in the pupa-stage. The crop does not communicate 
with the middle of the oesophagus, as is normally the case in 
Lepidoptera, but is placed near the lower end and communi- 
cates with the hinder part, not by means of a long slender 
canal, but, on the contrary, it opens into the oesophagus at 
the broad end, imperceptibly passing into the sac-like portion. 
The crop is formed thus in the last stage of the development 
of the digestive apparatus in the pupa, when it is not placed 
any more forward, and its commencement does not form a 
stalk. 
The salivary glands are feebly developed. They consist of 
two long slender tubes, one end of which opens into the lower 
part of the mouth ; the other end is usually rounded. 
The Malpighian vessels present no peculiarity, being 
arranged on the usual type found in Lepidoptera. On each 
side of the alimentary canal are two vessels, opening into the 
commencement of the small intestine. Each vessel consists 
of two tubes, one of which is simple, but the other forms a 
connexion between the two vessels. Near the openings of the 
two Malpighian vessels they form a very small oblong expan- 
sion, the rudiment of a urinary bladder. 
The heart or dorsal vessel is a long and rather narrow 
tube with several constrictions. There are eight chambers 
and attachments for the alee musculares on the dorsal surface. 
The respiratory system is arranged as follows : — There are 
two large respiratory tubes on the ventral surface, running 
along the whole trunk of the insect, and communicating with 
it by means of two transverse arching tracheas. At the hinder 
end of the body they are connected by means of a transverse 
tube. Numerous fine branches are distributed to the various 
internal organs, and from these also run smaller transverse 
branches which communicate with the spiracles. The air- 
