SCIENCE-GOSSIP. 



in others it reached l" mm. On the surf ace of a 

 stone about 18 inches across, Kit; of these cases 

 were counted, tn the same stream, larvae of 

 Simulium were abundant ; and as they were found 

 in plenty on the stones on which the rases of the 

 Hydropsyche occurred, Howard concludes that 

 they furnished the principal food of the latter 

 creature, lie thinks it certain that cumbers of 

 the larvae of the Dipteron would be washed into 

 the funnel-shaped nets ; and the owners of the nets, 

 eii.M'uneed within, appeared to be waiting for prey 

 to be thus brought to them( 8 ). Further, on 

 8 i /« ii li u in -covered rocks at Ithaca, N.Y., Howard 

 again found nets and tubes of Hydropsyche in 

 numbers. The nets differed somewhat from those 

 just described, and the observer supposes that they 

 were the work of a different species ('). 



Previously to the publication of these facts, Fritz 

 .Midler had recorded the occurrence of a net-making 

 Hydropsychid-larva in Brazil, and had established 

 for it the genus Rhyacophylax, Its cases, he says, 

 are rather rude canals, covered with irregularly 

 interwoven' vegetable fibres and each has, at its 

 mouth, a funnel-shaped verandah, covered with a 



pi ally made on specimens in captivity. When 

 a lar a is placed in a vessel of water, he says, it at 

 once legins to explore it - new quartet - 



Lily -i Lects a site for its dwelling. This is 

 made uf silken threads, and when completi 



re consists of a tube considerably longer 

 and broader than its occupant, and open al 

 ends. Ft is supported and strengthened by a 

 work of silken threads, which spread out for a 

 considerable distance, and are attached to surround- 

 ing objects. From time to time the larva turns in 

 its case, and even leaves it for a short space. 

 Generally, however, it remains quiet inside, appa- 

 rently on the alert for prey : 



" If a Chironomus or other small aquatic larva 

 approaches, it is almost certain to get entangled in 

 the network of silken threads. At once the Caddis 

 in its retreat perceives the presence of a possible 

 victim. The long hairs which cover the body are 

 possibly tactile, and reveal slight disturbances of 

 the silken network. The Plectrocnemia then pro- 

 ceeds warily to determine the cause of the disturb- 

 ance. Should the Chironomus be entangled near 

 the middle of the tube, the Caddis-worm does not 

 hesitate to bite its way through the side, and its 



Ax Insect-larva's Sxare ( 5 ). 



beautiful silken net. The creatures live in rapid 

 rivulets, and the entrance of the verandah is always 

 directed up stream, " so as to intercept any eatable 

 things brought down by the w^ater." The cases are 

 placed on stones, and a number are generally built 

 close together, so as to form transverse rows. 

 Miiller mentions having once seen, on a large stone, 

 about half a dozen parallel rows, of which one 

 alone was composed of some thirty cases ( 6 ). 



We have, further, interesting notes by T. H. 

 Taylor, on the larva of Plectrocnemia, another Hydro- 

 psychid, which occurs in swift streams on a stony 

 bed. When a stone was lifted out of the water its 

 under-side was found to be covered with patches of 

 mud from which the larvae emerged and began to 

 crawl about ; the patches were held together by a 

 binding substance, and were evidently the retreats 

 of the larvae. Taylor's observations, however, were 



(3) Howard, in Riley, /.<■., p. 510. 



i 1 i Howard, " Insect Life," i. (1888), pp. 100, 101. 



(6) Case ami net of the larva of a caddis-fly (Hydropsyche), 

 enlarged about four diameters. Alter Clarke, " Proceedings of the 

 Boston Society of Natural History," xxii. (1882), p. 67. 



(6) P. Mullet-, "Trans. Ent. Soc London," 1879, pp. 131- 

 t it. 



jaws very soon quiet the struggles of the prey. 

 There is some resemblance between the snare of 

 the Plectrocnemia and the web of a Spider, but 

 the Plectrocnemia is effectually concealed by the 

 mud which clings to its retreat. In captivity it 

 forms a web which is free from foreign particles, 

 and allows all its manoeuvres to be observed " ( 7 ). 



The contrivances about the tubes of Hydro- 

 psychids now described make the most satisfactory 

 approach to the unique position of the snare-spin- 

 ning spiders, of which the writer has yet heard. 

 Their function cannot reasonably be doubted, and 

 it is interesting to note that they are unhesitatingly 

 referred to as "snares" by Sharp as well as by 

 Taylor. The threads are probably not viscid : bur 

 even in the case of spiders viscid lines occur only 

 in the snares of one or two groups. 



The silk-glands of caddis-worms are often of 

 great development; and the spinneret, like that of 

 larvae of Lepidoptera, Diptera, and Hymenoptera, 

 is oral. 



(To be continued.) 



(7) Taylor, in Miall, "Nat Hist, of Aquatic Insects, 

 pp. 265-267; 



