THe Biotocy or EPHYDRA SUBOPACA LOEW 597 
a cord, or any other object, either immersed in, or exposed outside of, 
the water. All will, however, live through the transformation period. 
Failing to find any other object of attachment, a larva may grasp the 
dorsum of another larva’s abdomen. Three or four, or even more, may so 
hold together and drift around in water. 
The spiracles in the prothoracic stigmas and at the caudal tips. are 
still functional after pupation has commenced, and continue so until 
the internal metamorphosis is completed, when the tracheal trunks become 
atrophied. The air stored within the puparium will be sufficient for the 
needs of the pupa for the time being. When the pupa matures and more 
air is needed, the adult will emerge. 
The puparium is brownish, with pigmented spots on the dorsum. A 
well-pronounced edge is formed around tue margin of the anterior end. 
The prothoracic stigmas now stand out laterally. Each is conspicuous 
with its four digits. The branches of the caudal process diverge laterally 
instead of pointing straight backward (Plate LVII, 42). When the pupa 
matures, its body contracts and separates from the wall of the puparium. 
The pupa is enveloped now in a transparent membrane. The head 
is broad, with two small antennal tubercles and well-shaped compound 
eyes. The proboscis is flattened in a truncate piece closely overlapping 
the coxae of the anterior legs. All three pairs of legs are closely pressed 
ventro-laterally. The wings are ensheathed by membranes, through which 
the convolutions of the veins are visible. Closely cephalad to the base 
of each wing there is a brown, knob-shaped spiracle (Plate LVII, 41). 
Length of pupal period 
The length of the pupal period varies greatly. The amount of food 
that the larva has taken before pupation, the location that the pupa 
seeks, temperature and moisture, rain and sunshine, and the salinity and 
the density of the water — in other words, both the internal and external 
conditions — have considerable influence upon the development of the 
pupa. Pupation records made in the laboratory are as follows: 
Beginning of pupation Emergence of adults Number of days 
June 29 July 10 11 
June 30 JulyaeO 6 
July 26 August 4 9 
