XXI 



CADDIS-FLIES 



481 



their geographical distribution is, however, by no means peculiar 

 to them, for a similar discontinuity of distribution exists in 

 numerous other groups of Insects, and even in other divisions 

 of the Phryganeidae. 



The Phryganeides almost without exception inhabit still waters, 

 and it is more specially to them that the brief sketch of meta- 

 morphosis given in the preceding pages will be found to apply. 

 The larva always has the respiratory filaments simple and thread- 

 like, though elongate, and lives in a case that it carries about ; 

 this case is open at both ends, and the larva is said to occasionally 

 cut off the end having the least diameter and increase the other 

 end, thus accommodating the habitation to its own growth. 



Limnophilides. These Insects have only three, instead of four, 

 joints in the maxillary palpi of the male, but in most other respects 

 agree with the Phryganeides. There is, however, greater variety 

 in the habits of the larvae, though all live in free cases. In the 

 genus Enoicyla (Fig. 

 326) we meet with the 

 anomaly of a Trichopter- 

 ous Insect that lives 

 amongst moss and dead 

 leaves, far away, it may 

 be, from water. The cases 

 of the Limnophilides are 

 constructed of a great 

 variety of materials, and 

 are often decorated with 

 shells containing living 

 inmates. 



In the genus Ajpa- 

 tania the phenomenon 

 of parthenogenesis is 



thought to occur, there being at least two species in which no 

 male specimen has ever been discovered, though M'Lachlan has 

 made special efforts to discover the sex of A. muliebris. It 

 should, however, be stated that these species have not been ex- 

 tensively investigated ; A. arctica has been detected in the Arctic 

 regions, and A. muliebris has occurred in several localities in 

 Europe, in Britain chiefly near Arundel in a lake of intensely 

 cold water. 



VOL. V 2 I 



Fig. 326. Metamorphoses of Enoicyla pusilla. 

 (After Ritsema.) A, Case of full-grown larva ; B, 

 larva and case niagiiitied ; C, larva extracted ; D, 

 wingless adult female ; E, male. 



