152 



HARDWICKE'S SCIENCE-GOSSIP. 



[July 1, 1S6S. 



colour is seen. I give these few birds as typical 

 cases, but I could instance many more where the 

 coincidence of colour is very striking. I have 

 nearly forty cuckoos' eggs taken in situ, and have 

 compared full sixty more with like success. I 

 mention this in hope that some of your correspond- 

 ents may be able to bring forward instances in 

 support of this curious theory. 



C. 0. G. Napier. 



CADDIS-WORMS AND THEIR CASES. 

 By R. McLachlan, E.L.S. 



AMONGST the many marvels of insect-life, none 

 are more curious thau the devices whereby 

 the otherwise defenceless larval condition is enabled 

 to sustain itself in the struggle for existence. To 

 enumerate even a few of these would require more 

 space than could possibly be allotted to me here ; 

 and, moreover, my present subject is connected 

 with one particular means of defence, — the building 

 by the larva of a house in which it constantly lives, 

 and under the protection of which it can, in most 

 instances, roam about at its pleasure in search of 

 food. But few Coleopterous larvae are architects ; 

 but, notably, some beetles (Clythra, Cryptocephalus, 

 &c.) form a case which acquires great hardness and 

 solidity. Many Lepidopterous caterpillars live in 

 self-made houses, sometimes formed of a coarse 

 silk secreted by them, but more generally of vege- 

 table matters fitted on to the outside of a silken 

 tube, or lined with silk. The small moths of the 

 genus Coleophora all possess this habit, and also 

 the whole of the singular family Psychidce. Eor 

 these larvae the Germans have invented the very 

 expressive term " Sacktriiger." With these I have 

 nothing to do here. This paper is intended to elu- 

 cidate the habits of the insects known as Caddis- 

 flies, by some considered as a separate order, and 

 termed Trichoptera ; by others placed as a division 

 of the great order Neuroptera. 



Every disciple of " the gentle art " is familiar 

 with Caddis-worms, which, when divested of their 

 fortresses, form bonne-bouches to most fresh-water 

 fish. But though these creatures are so well known, 

 there remain much ignorance and popular miscon- 

 ception of their actual habits. With one or two 

 exceptions, all larvae of Caddis-flies are aquatic, and 

 reside in fresh waters ; some frequenting ponds, 

 lakes, &c. ; whereas others delight in the turbulence 

 of the most impetuous torrents and waterfalls. 

 With the assistance of our artist, I here attempt to 

 familiarize my readers with some of the more usual 

 and striking forms of cases. Eirstly, in ponds and 

 slowly-flowing canals, one frequently finds long 

 cylindrical tubes formed of pieces of leaves and 

 other vegetable matters neatly arranged in a spiral 



form, left to right, or vice versa. These are formed 

 by species of the true genus Phryganea, and by some 

 allies. Cases of this kind are nearly of equal diameter 

 throughout, and the larval inmates have the power 

 of turning themselves, and thus of presenting then- 

 heads at either end (fig. 144). Species of the genus 

 Limnephilus make what are, perhaps, the most fami- 

 liar cases ; viz., those formed of shells, seeds, pieces 



Fig. 144. Case of Phryganea grandis. 



of wood and rushes, twigs, &c, arranged in various 

 order. A tolerably common case is that of L. rhom- 

 hicus, which uses pieces of moss, cut lengths of rushes, 

 &c, and arranges them in a transverse and some- 

 what oblique direction, forming very bulky masses 

 (fig. 145). A very abundant species, L.flavicornis, 

 also frequently forms a similar case, but it by no 



145. 



146. 



147- 



150. 



151. 



Fig. 145. Case of Limnephilus rhombicus. 

 Figs. 14G to 151. Cases of Limnephilus flavicornis. 



means confines itself to the use of vegetable matters 

 only ; for most of those beautiful shell-structures so 

 common in ponds and deep ditches are the work of 

 this insect. It seems to be a most capricious crea- 

 ture, sometimes selecting myriads of some one 

 species of minute shell or seed, with which it builds 

 its house entirely ; again, it appears to form a fancy 

 building made of many substances, but at pretty 

 regular intervals ; again, it will use almost any 

 substance, vegetable, animal, or mineral, and work 



