8o . INSECTS. 



of the grains of mould, to which consistency is given by means of a gummy secre- 

 tion furnished by the larva. Many form with this secretion a hard case, the outer 

 side covered with chips of the surrounding bark, which, owing to their similarity to 

 the surroundings, serve as a protection from observation. Others spin a silken egg- 

 shaped cocoon, sometimes flocculent and broken, sometimes formed of yards and 

 yards of silken thread, emitted from the mouth and passed over and under, across 

 and rOund, until the cell is complete. Amongst the more interesting of these, 

 cocoons is that of the emperor-moth, which forms a short tubular exit closed 

 against the entrance of earwigs and other insects by a circular series of fine bristles 

 directed outwards and converging to a point. The principle of contrivance is the 

 same as that employed in the manufacture of lobster-pots ; but here the process is 

 reversed, for in this case it admits of a ready egress but prevents any entrance. 

 Moths whose pupa stage is passed within an external cocoon have a double task 

 before them when the time is ripe for an emergence. The pupa itself — as does also 

 the chrysalis of butterflies — splits at the dorsal suture above the thorax, and the 

 moth emerges, ferreting a way through one end of the cocoon, which seems to be 

 softened by moisture from within, and thus escapes. The imago, or perfect insect, 

 having now emerged, climbs to some point of vantage, where the wings, still very 

 small, though completely formed, are allowed to hang downwards, expand and 

 harden in the air. After a few hours they are stiff and ready for use. 



At no stage in their lives are lepidopterous insects free from the 

 Enemies. . . 



attacks of enemies. In the egg-state they fall a prey to beetles and 



small birds, and as larvae they are extremely liable to receive a deadly thrust with 



the ovipositor (or sting) of an ichneumon. As the ichneumon-grubs grow at the 



expense of their host, scarcely a tissue in the whole body may remain, save those 



needful for the carrying out of life-supporting functions. And at last, when the 



grubs are themselves ready to pupate, and have no further need of their host, they 



finish up the rest and the larva dies — chiefly because there is nothing left to live. 



The enemies of the imago, whether butterflies or moths, are numerous. Birds, 



bats, dragon-flies, etc., pursue and harass them whenever they happen to meet with 



them. The marvel is that any remain alive to lay eggs and perpetuate the species. 



In the struggle to escape detection and capture, all unconscious 



though it may be, arises the phenomenon alluded to above, and known 



as protective mimicry. The kindred phenomenon of protective colouring, when the 



moth or butterfly merely resembles in hue the bark, leaf, or twig on which it 



rests; also protective resemblance, simply when insects take the form of objects, 



such as twigs, dead leaves, bits of decayed wood, flakes of white bird-droppings ; these 



are all well known. But protective mimicry means more, it implies the actual 



mimicking either the form, colour, or habits of some other insect which is either 



too savage or unpleasant to make it a desirable object of food ; as, for instance, 



the clear-wing moths mimic gnats, bees, wasps, ichneumons, etc. Perhaps the 



most curious instance is that of the Kallimas or dead-leaf butterflies of Northern 



India, whose upper sides are richly coloured, while the under sides are dull brown 



mottled and veined with darker colours. So conspicuous a butterfly would not 



fail to fall a ready prey to foes. If it but settle for an instant, however, the 



sharpest eye will not detect them. The secret lies in the colour and veining of the 



