CADDIS-FLIES. 85 



galleries. When full grown it constructs a large and 

 extremely tough silken cocoon, covered on the outside 

 with very numerous minute stones. It is generally 

 situated on the side of a large boulder, just at the point 

 where the stone is embedded in the sandy detritus of the 

 river-bed. These cocoons are extremely difficult to 

 remove without destroying the contained pupa?, and it 

 is quite impossible to extract the insect without injury, 

 owing to the tough, but very elastic, nature of the cocoon, 

 which when pulled in one direction stretches and con- 

 tracts in the other, thus compressing and injuring the 

 enclosed insect. The cocoons are often very abundant 

 in February, but I have only succeeded in getting one 

 specimen as far as the swimming pupa stage, from which 

 I was able to identify the insect as P. puerilis. Both 

 larva and pupa very speedily die in confinement, the insect 

 being apparently especially susceptible to the ill-effects of 

 the imperfectly aerated water of the ordinary aquarium. 

 The perfect insect appears from November till April. It 

 is nocturnal in its habits and is often attracted by light. 

 The specimens taken in November appear to emerge from 

 pupae, which have passed the entire winter in their cocoons 

 in the streams ; this appears to be a frequent habit with 

 P. puerilis, as I have several times found the pupae in 

 streams during the winter. 



Sub-Family 4.— RHYACOPHILIDES. 



In this group the larval habitations are fixed. The 

 pupa is enclosed in an inner cocoon, lying inside the 

 original habitation of the larva. 



Genus HYDROBIOSIS, McLachlan (1870). 



"Antennae slender, the basal joint shorter than the head, and stout. 

 Maxillary palpi long and pubescent, the two basal joints short and stouter 

 than the others, fifth not so long as the third and fourth together. 

 Anterior wings elongate, the costal and dorsal margins nearly parallel ; 

 the apex longly elliptical, clothed with woolly pubescence and longer hairs 

 on the veins ; fringes short ; neuration not very distinct. Posterior wings 

 shorter and broader, folded, rounded at the apex; fringes long on the 

 dorsal margin ; pubescence slight ; no closed discoidal cell ; a transverse 

 vein unites the upper branch of the sector with the radius ; a second 

 unites the lower branch of the sector with the superior cubitus, and a 

 third is placed below this, much nearer the base of the wing. Spurs 

 2.4.4; those on the anterior tibiae small, on the others long and 

 straight. 



" Distribution. --New Zealand" (Hutton). 



