CADDIS-FLIES 



481 



tribution is, however, by no means peculiar to thern, for a similar 

 discontinuity of distribution exists in numerous other groups of 

 Insects, and even in other divisions of the Phryganeidae. 



The Phryganeides ahnost 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-Hke, thoiigh 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, 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 Hving 

 inmates. 



In the genus Apa- 

 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. muliehris. It 

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

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

 regions, and A. muliehris 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 Eitsema.) A, Case of full-grown larva ; B, 

 larva aud case magiiilied ; C, larva extracted ; D, 

 wingless adult female ; E, male. 



