Henry Gardiner Adams, The Wild Flowers, Birds, & Insects of the Months, Londres, James Hogg and Sons, 1862, p. 44-46 : chap. « Proofs of design ».
« Before quitting the pond and the river brink,
« Where water-liles mount their snowy buds,
On whose broad swimming leaves of glossy gren,
The shining Dragon-fly is often seen »
as Clare has it, we should briefly notice those strange sub-aqueous architects, the Caddis-worms, which are the larvae of the four-winged flies in the order Trichoptera of Kirby and Spence.
Before going into the pupa or chrysalis state, these worms construct for themselves a case, or covering, of whatever materials come readiest to hand, such as sand, and stones, shells, wood, or leaves ; these are carefully joined or cemented together, so that they form a perfect and compact, although frequently an incongruous looking whole : the Inside is generally smooth and comfortable, but the outside rough and rugged enough, and of all imiginable shapes. « It is », say the Entomologists above quoted, « a covering as singular as if a savage, instead of clothing himself with squirrel skins, should sew together into a coat the animal themselves ». Rennie, in his « Insect Architecture », gives cuts of some of these curious habitations, some of which afford good spécimens for the conchologist, having several varieties of shells glued to the outside ; having several varieties of shells glued to the outside ; some in which the materials were of too great a specific gravity, have been rendered sufficiently buoyant for the purpose of the builder by the addition of a piece of light wood or hollow straw ; in running streams, where the tiny habitation would be liable to be swept away, the case, if composed of very small stones and sand, is frequently found with a larger stone added by way of ballast, and sometimes it is even anchored by means of a silken cable to something sufficientlyy firm to resist the force of the current. Patterson tells us that, « to protect themselves from attacks of their enemies, and at the same time to give admission to the supply of water essential to their existence, the Caddis-worms adopt an ingenious expedient. They construct a kind og grating, which they fix across each extremity of their domicile, and thus provide at the same time for respiration and defence. It is stated that this grating is formed of a strong description of silk, which the animal has the power of spinning, and which assumes although under water, the necessary degree of consistence. In one of the cases in my possession, it is formed of a mass of minute portions of vegetable matter, so thick as almost to exclude water ; and two holes are formed at the sides of the case, close to the extremity, for the ingress of the fluid. In another, some small bivalve shells are agglutinated together ; and as their convexity leaves some vacnt spaces betwen each shell, the object of the gratin gis attained by a different procedure. It would seem , therefore, that the larvae, although endowed with power of forming a silken network, avoid the trouble of doing so, where the abundance of suitable materials of a different description renders such labour unnecessary.
Here are proofs of design and adaptation, even among the lower animals of creation, which make us blush for our boasted reason, and inclined to exclaim, in the words of Mrs Sigourney to the Coral insects of the ocean,
« Toil on ! for the wisdom of man ye mock,
With your sand-built structures, and domes of rock »
But we must now leave the watery world whose insect inhabitants we have yet but imperfectly examined, and…. »