74 GNATS Oil MOSQUITOES — CHAPTER V 



oviducts uniting behind to form a median oviduct, a median 

 copulatory pouch, and three spermathecae opening into the 

 last. They correspond in size and position to the testes. 

 The median oviduct is formed by the invagination of a 

 region which Dr. Hurst takes to be the ninth sternum, 

 while the anus opens at the posterior end of what he takes 

 to be the eleventh abdominal somite, so that there is no 

 common cloaca. This invagination is already far advanced 

 at the beginning of pupal life, and during it it grows 

 forwards, keeping pace with the forward shifting of the 

 last pair of ganglia, and at all stages lying just behind it 

 till the final ecdysis, when the rapid shifting of the ganglia 

 leaves it behind. Its anterior end is, in the adult, near 

 the front of the seventh segment. In the youngest pupae 

 three flattened invaginations, the future spermatheca?, lie 

 on the dorsal wall of this median oviduct. During the 

 pupal period the anterior end of each becomes spherical and 

 acquires a strong chitinous lining. The anterior ends of 

 these organs remain stationary in the eight segment 

 throughout. The bursa copulatrix is a dorsal outgrowth 

 of the invagination which gives rise to the median oviduct, 

 and is a small pouch lying just behind and above the median 

 aperture. 



The pupa does not eat. It breathes air through the 

 apertures at the end of its syphons. It floats, thorax 

 upward, by virtue of the large air cavity lying under 

 the hinder part of the thorax and front of the abdomen. 

 This cavity is bounded in front by the legs, at the sides by 

 the wings, and in front by the mouth parts. It extends 

 up at each side of the abdomen, where it is covered by 

 the halteres, and into it opens the patent first abdominal 

 stigmata. The pupa is sensitive to light, and immediately 

 darts backwards when a shadow falls upon it suddenly. 

 The movements, however, though very rapid, are devoid of 

 anything like steering. 



The larva has to search for food, but the pupa has 

 simply to get out of the way of danger, and the direction 

 of its fiight is of little importance, though since the move- 

 ment is always backward with reference to the pupa, it is 



