June 1, 1893.] 



KNOWLEDGE. 



105 



Though the cases of the r.si/rhidfr in this country are, in 

 consequence of tlieir small size, prohably known to none 

 but professed entomologists, the much larger species of the 

 tropics have attracted general attention, and thus have 

 acquired popular names. A certain South African species 

 goes by a complex and unpronounceable native name which, 

 it is said, may be rendered in English, " he that goes with 

 his little house " ; and again, in the Colonies, some are 

 known as " walking chips," from the sticks with which 

 the cases are covered. One of these now before me con- 

 sists of a silken tube, the central portion of which is 



Fig. 10. — Cases of PsyehidiB, imitating shells ; magnified two 

 diameters. (After McLachlan.) 



strengthened and made stiff and unyielding by seventeen 

 bits of stick placed longitudinally side by side ; all, except 

 one, are of nearly the same length, being about one and a 

 quarter inches long ; the single exception is nearly twice 

 this length, and the extra length projects at the hinder 

 end, since it is necessary for convenience of locomotion 

 that all should terminate at about the same level at the 

 mouth end. The ends of the sticks show a rounded bitten 

 surface, where the caterpillar has nibbled them off, and 

 remind one a good deal, though on a small scale, of the 

 similarly rounded ends of the sticks bitten off by beavers. 

 The parts of the tube that project beyond the sticks are 

 covered with small fragments of bark, &c., irregularly 

 placed, and not interfering with the flexibility of the tube ; 

 hence, when the caterpillar is on a leaf, the case bends at 

 this part, and hangs downwards in whatever position the 

 insect may be. Amongst nations which believe in 

 the transmigration of souls, there has sprung up the 

 idea that these bundle-bearing insects are the souls 

 of men who, during a former life, have stolen firewood, 

 and are therefore condemned to do penance by being 

 subjected to the drudgery of perpetually carrying about 

 burdens of such a character as to remind them of their 

 former fault ! 



The cases of the Psychidic forcibly remind us of another 

 set of insects which make habitations almost identical in 

 form. " Caddis worms " are well-known inhabitants of 

 ponds and streams. They are caterpillar-like creatures 

 which may often be seen dragging about their little tubular 

 homes, which are ornamented on the outside with twigs, 

 roots, bits of stick, dead leaves, sand grains, gravel and 

 shells. Some of them, again, make cases which are spirally 

 coiled, and so look like snail shells, thus closely resembling 

 the spiral cases above mentioned. Now if one were to find 

 an empty case of one of these creatures, and were to know 

 nothing of its history, not even whether it belonged to an 

 aquatic or a terrestrial insect, it would scarcely be possible 

 to tell whether it was a caddis case or belonging to one of 

 the Pttychidw : and yet the perfect insects are considerably 

 unlike in structure, and are referred to two different orders. 

 The caddis flies, from the absence of the scales on their 

 wings which characterize butterflies and moths, and from 

 peculiarities of the mouth organs, are referred to the 

 Neuroptera, while the butterflies and moths constitute the 

 Lepidoptei'a ; and yet we find that certain species in each 



order have acquired such closely similar architectural pro- 

 pensities that, although the one set are terrestrial and the 

 other aquatic, and although the protection in the one case 

 is apparently against fishes and in the other against birds, 

 the products of their sidll are scarcely to be distinguished 

 from one another. Between the spiral cases of both these 

 groups of insects and the shells of the Mollusca which they 

 mimic, a point of contrast should be noted. The shell of 

 a mollusc is a secretion from its own body, to which it 

 remains attached at a certain point ; it is, in fact, a 

 skeleton rather than a house, though an external one. 

 But the spiral case of the insect, on the other hand, is not, 

 except for the silk it contains, a secretion of its fabricator, 

 but is largely built up of foreign matter, and is nowhere 

 attached to the creature's body, so that it is a true house 

 and in no sense a skeleton ; it can therefore be changed 

 at pleasure, which of course is not the case with a mollusc's 

 shell. 



Turning now to the Tine;?, we find several groups of 

 insects indulging in the habit of fabricating cases. .Just 

 about the present season of the year, there may be seen La 

 woods, either resting on the fresh green leaves or fluttering 

 about in the sunshine, a tiny moth with shining dark 

 brown wings which have two little yellowish spots on their 

 inner margins, and with a red head and strongly comb- 

 like antennffi. This is called Incurvari<( muscalella. It 

 was hatched from the egg nearly a year ago as an 

 insignificant and uninteresting -looking grub, which, as 

 soon as it was out of the eggshell, set to work to mine into 

 the leaf on which it found itself. It spent the first few 

 days of its life as a miner, but soon forsaking this habit, it 

 cut out the roofs of its mine in -June, and fastening them 

 together into a flat case, ensconced itself within and 

 descended fi-om the branches to take up a humble position 

 on the ground. Here it lived a haphazard life, eating 

 either dead brown leaves or fresh green ones, as occasion 

 served, and growing very slowly, for it had a long period of 

 larval life before it, and even by the end had not to attain 

 to any great size. It formed fresh cases for itself as its 

 slow growth necessitated. It was full fed in October, but 

 did not choose that time to pass into its next stage. Safely 

 protected in its flat oblong case, it lay about amongst the 

 dead leaves during the winter in a torpid condition. But 

 when spring arrived, it awakened to renewed vigour and 

 became a chrysalis, from which the moth issued as soon as 

 the sun's beams had attained sufficient power to entice it 

 out. Several other allied species have similar habits. 

 The beautiful little moths called " longhorns," with 

 metallic wings and antennae many times as long as the 

 body, are nearly related to these, and are also case-makers. 

 The perfect insects, some of which are very abundant in 

 woods just now, flutter round the tops of the bushes in the 

 bright sunshine, and at a distance look something like 

 gnats. 



But perhaps the most noted of all the case-forming 

 caterpillars are the members of the genus Coleophora, 

 which have received that name in consequence of this 

 habit, the word being Greek for a sheath-bearer. They 

 are very small and inconspicuous moths, mostly of exceed- 

 ingly plain appearance, and as they are of very retiring 

 habits to boot, would certainly never be noticed by the 

 casual observer. We have a great number of species in 

 this country, and the caterpillars' cases are much more 

 frequently seen than the perfect insects, though, being 

 small, they need to be carefully looked for. Amongst the 

 difl:erent species there is an endless variety in the shape 

 and appearance of the cases (Fig. 11), but the habits of 

 each species are extremely uniform, so that the nature of 

 the case is generally a good guide to the determination of 



