1912] Life History of a New Psychoda : 417° 
exposed. It is rather sluggish and moves about slowly from 
place to place by means of ‘a wriggling movement of the 
abdomen. 
A large number of pupz were measured and it was found 
that the average length exclusive of the respiratory tubes was 
4.5 mm. The range of variation was from 4.02 mm. to 4.86. 
The greatest diameter which is in the region of the developing 
wings had an average length of 0.84 mm., the variation being 
0.72 mm. to 0.9 mm. When first transformed the pupa is pale 
in color like the larva but soon becomes darker. 
The head and thorax with their accompanying parts are usually deep 
brown. The thoracic respiratory tubes (Fig. 9, Pl. XX XII) are long and 
slender. Measurements show the average length to be 0.58 mm. and the 
extremes of variation from 0.54 mm. to 0.66 mm. Each consists of two 
parts, a short, yellow, indistinctly wrinkled, proximal stalk, and a 
much longer, dark, distal part. The latter has its maximum diameter 
at the base and tapers gradually towards the tip. Under magnification 
it shows a large number of fine transverse wrinkles. On the dorsal 
surface two approximately parallel rows of small clear circular spots 
extend from the base to the tip and there are aggregated into a small 
terminal cluster. According to Miall and Walker (1895, p. 146) these 
spots are the external openings of the large trachea which traverses the 
organ. Dell (1905, p. 303) however, has shown in Psychoda sexpunctata, 
a European species, that in places the tracheal extension bulges through 
the wall of the respiratory tube thus giving rise to the clear circular spots. 
The abdomen is widest at its junction with the thorax and it grad- 
ually tapers caudad. The spines along the lateral margins are mod- 
erately developed and each normally ends in a fine stiff hair. The inter- 
segmental grooves are both wide and deep, distinctly marking off the 
segments. Chitin is minimized in these intersegmental grooves and this 
accounts for the ability of the abdomen to perform rather active move- 
ments. These grooves are also much lighter in color than the contiguous 
parts thus giving the abdomen a banded appearance. The regions 
between the intersegmental grooves are strongly chitinized. Each 
bears an armature of spines on both the dorsal and ventral surfaces. On 
the former there is a single row of spines on the caudal margin of each 
segment while on the latter there are two rows on each segment, one 
near the middle of the segment and composed of large spines only, the 
other on the caudal margin of the segment and composed of large and 
small spines. Figures 1 and 2 show the number, comparative sizes, and 
disposal of these spines on the two surfaces. The examination of a large 
number of pupz showed that the size and arrangement of these spines 
are constant and that there is only a very slight variation in the num- 
ber, the variation being confined to the small spines. These small spines 
may be simple or compound (with double tips)and those on a given segment 
may vary to the amount of one or two in different specimens. The dor- 
sal surface of the base of the last segment bears two simple laterally 
projecting spines and two similar spines occur on the ventral surface. 
