on the labrum, ends of the mandibles and anal rods or lobes; labrum and 

 mandibles are used for cleaning the openings of the anterior membrane; 

 the anal rods are used to clean the posterior openings. The crotchets of 

 the presegmental plates support the pupa when it moves forward to clean 

 the anterior membrane; movements backward are made possible by the 

 support of the anteriorly directed crotchets of the postsegmental plates; 

 because the anterior membrane clogs more rapidly than the posterior 

 membrane, more work is necessary to clean it. The plates with the 

 crotchets have to be disengaged for moves in any direction; when the pupa 

 moves backward, its body contracts, the presegmental plates near the 



101 anterior margin of the segment are covered by the posterior margin of the 

 preceding segment and the pupa can move posteriorly. When the pupa 

 moves forward, the postsegmental plates change their position; they retract 

 and become inclined, descending slightly forward and inward; their setose 

 surface then becomes disengaged from the walls of the case on which the 

 presegmental spines are engaged and the pupa moves forward. 



The clinging apparatus also functions when the pupa emerges from the 

 case; it is therefore present in pupae of Annulipalpia. 



The cleaning apparatus of the pupae varies markedly. Cleaning usually 

 is performed by the setae at the anterior and posterior ends of the body 

 (Figure 160). In the pupae of Leptoceridae (Figure 16l), the anterior slit 

 of the case is cleaned by biting with the mandibles; the anal rods move 

 separately and together during the cleaning of the posterior opening. The 

 pupae of Molanna, the ventral side of which is diverted to the dorsal 

 wall, introduce the tips of the mandibles into the dorsal slit (Figure 162). 

 The pupae of Odontocerum albicorne clean the slit at the anterior 

 end of the case by biting with the long, curved and narrow end of the 

 mandibles (Figure 163). 



The pupae of some species (Goera pilosa, Silo pallipes, 

 Potamophylax n i g r i c o r n i s, Odontocerum a 1 b i c o r ne) are 



1 02 parasitized by wasps of the genus Agriotypus (A. armatus, A. gra- 

 cilis). Observations on the host, parasite and the latter's life cycle have 

 been reported by Klapalek (1889), Clausen (1931) and Fischer (1932). 



Emergence of adult insect 



Emergence from the case. When the development of the pupa 

 is ended, and the imaginal organs are developed, the pupa leaves the case; it 

 leaves the water, molts and the imago hatches; if this is inhibited, the insect 

 dies. The pupa tears the membrane of the case with the denticles of the 

 mandibles (Figure 164); when the insect molts, it discards the muscles of 

 the mandibles together with the pupal exuviae; the denticles of the mandibles 

 wear off markedly when the pupal case is torn. 



The pupa uses its presegmental plates and anal legs to leave the case 

 and begin to swim. The pupa is very mobile; some pupae swim with the 

 dorsum downward, like Notonecta. Large species swim more slowly than 

 small species; the pupae of the small species of the family Hydroptilidae 

 move so rapidly that it is difficult to follow the movements of their legs. 



93 



