Life-history of Phalacrocera replicata. 309 
had taken a dark-green colour. The fly appeared on 
Oct. 27th, so that the pupal stage lasted eleven days, 
unusually long in comparison with other aquatic Diptera.* 
The cast pupal skin was found to be attached to a leaf of 
moss by the dorsal projections from the hinder abdominal 
segments, 
9. The pupe. 
The pupa differs strikingly from the larva in its habits. 
It is comparatively active, and moves when requisite by 
flexion of the abdomen. When laid on the hand, it 
wriggles about, bending its body almost into a circle. 
The usual attitude of the pupa is vertical, the prothorax 
with the respiratory tubes just reaching the surface of 
the body; the pupa maintains itself in this position by 
grasping fioating weeds with its dorsal abdominal hooks. 
Considerable disturbance of the water does not cause it 
to loose its hold. The pupa is also found at times 
floating at the surface ; if turned over, it recovers its 
ordinary position, which is necessary to respiration, by 
movements of the abdomen. Sometimes it descends to 
a fair depth from the surface by the help of the weeds. 
The pupa is asphyxiated by a submergence of six 
hours. 
lts length varies from three- to four-fifths of an inch. 
Its general colour is greenish-brown ; there is a darker 
band along the mid-dorsal line, besides a median and two 
lateral dark bands on the ventral surface. ‘lhe body is 
flattened dorso-ventrally, and produced laterally into thin 
margins, as inthe Chironomus pupa. A pair of respiratory 
tubes project trom the prothorax, diverging strongly 
from each other. ‘The sixth and eighth abdominal 
segments are provided with dorsal projections, which 
serve to attach the pupa, and to prop it up in such a 
position that the prothorax is out of the water ; there are 
also ventral and terminal projections. The thoracic legs 
are short, not reaching beyond the third abdominal seg- 
ment. Rows of black dots are found on the dorsal, 
ventral, and lateral surfaces, whose arrangement is 
shown in figs. 15-15. 
** De Geer found that the pupal stage lasted only six days, and 
we have found the time variable according to the season and tem- 
perature. 
