558 ANTHON. [Vou. XIX. 
Xlwuvithe-eoPs 
When the larva reaches its full size, it has stored up a great 
amount of reserve food material in the sheets of adipose tissue ; 
it ceases to feed and becomes very sluggish until the last larval 
skin is shed and the pupa emerges. Pupation here usually 
takes place some time in April. The pupa is shorter than the 
larva and is proportionately wider. (Fig. 52.) When it first 
emerges it is very soft and very transparent, but as the parts 
becomes chitinized they turn a rich brown. The compound 
eyes, antenne, the labial palps and other mouth parts can be 
seen through the pupal skin, though the head is not marked off 
from the rest of the body. The three pairs of thoracic legs 
are short and do not reach beyond the first abdominal segment. 
The abdominal portion consists of the usual six segments, pure 
white save for the dark golden band down the ventral and 
lateral surfaces. On each of the lateral lines there are two 
brown projections, a large one near the posterior portion of 
the segment and a smaller one midway. On each median sur- 
face there are others; one on each side in the first two abdom- 
inal segments and two in the next four. The posterior seg- 
ment is, of course, sexually modified. The tracheal system of 
the pupa is closed, as there are no spiracles present. 
Since the posterior extremity is changed to conform to the 
corresponding segments of the adult, the sexual modifications 
are indicated. The female may at once be recognized by the 
long triangular valves which are to constitute the ovipositor. 
The posterior segment of the male shows no such modifica- 
tion, but ends bluntly and shows the transverse anal opening. 
There are three large lateral spines upon each side of the 
posterior segment, while the other segments only have one 
large and one small projection. The spines all project back- 
wards and serve to assist the animal in locomotion by giving 
it sufficient hold in the soft wood in which the pupa lies. It 
also enables it to creep to the surface before its final transfor- 
mation. Such aids are found in very many Dipterous larve 
and Dipterous pupe, for example in Dicranota, Tipula, and 
Bibio. If the pupa could not come to the surface befgre the 
