KNOWLEDGE 



[January 2, 1898. 



uamed from the white T-shaped mark contained in the 

 blue " eyes" on its wings. This fine insect is found in 

 several parts of the world, including some Em-opean 

 coTintries, though not in Britain. The newly-hatched 

 caterpillar is green with five red-forked and tuberculated 

 horns (Fig. 8), two pointing straight forward above the head, 



Fig. S. — Yiiung larva of Tan Emperor Motli, 

 magnified 7 clianietiTs. (After Poulton.) 



two projecting from the sides of the thorax, and one 

 pointing upward and backwards from the dorsal surface of 

 the last segment but one, just the position of the caudal 

 horn of the Sjihiiiifidir. The hair-bearing tubercles on 

 the rest of the body are also present, but small. This 

 remarkable appearance is retained by the caterpillar during 

 its first three stages, but at the next moult the whole 

 of the apparatus of spines and tubercles suddenly and 

 entirely disappears, the only trace of the former condition 

 being a general shagreening of the body similar to that of 

 some of the hawk moths. There are now also other 

 resemblances to the SjiliiniihUe, such as the assumption of 

 the sphinx attitude, and the presence of oblique coloured 

 stripes on the sides. Facts such as these, pointing as they 

 do to a kinship between the two great families of hawk 

 moths and emperor moths, evidently impart a new inte- 

 rest to the caudal horn of the former, and suggest that it 

 may be the solitary and modified remnant of a complete 

 ancestral armature, a monument of bygone times, and a 

 key to the past history of the race. 



A curious point is suggested in connection with these 

 horns, viz., as to the accommodation within the oval egg- 

 shell for caterpillars of shapes so awkward for packing up 

 into a small compass. The problem is not in all cases 

 solved in the same way. Before hatching, the horn of the 

 Sphiii'iid'i is flexible, and is bent round along the sides of 

 the eggshell ; but a different method of stowage is adopted 

 in the case of A;ilia fan. Here there are five horns instead 

 of one to be packed away, and tliey would evidently get 

 rather in the way if dealt wth in the same manner. 

 Accordingly, it is found that they are not of full size in the 

 egg, but appear as small curled tubercles, which expand 

 to the full form and size aftn- hatching, by the passage 

 into them of blood from the body, in much the same way 

 as the wings of a Lepidopterous insect are expanded after 

 it has left the chrysalis. 



From horns, tubercles, spines and tails the transition 

 is not difficult to hairs — in fact it is not easy to say where 

 spines cease and hairs begin ; the structures arc similar in 

 plan, and differ chiefly in diameter and in the degree of 

 flexibility or stiffness tjiat results therefrom. Hairs and 

 spines may be either simple or branched. Good examples 

 •of branched spines may be seen in the caterpillars of many 

 butterflies, such as the tortoise-shells, peacock, red admiral, 

 painted lady, and fritillaries. Densely hairy larva; are 

 specially characteristic of the group of moths called 

 Bombyces (tigers, ermines, eggers, &c.). The common 

 "woolly bear," or caterpillar of the garden tiger moth 

 I Anti,, r„i„\, mav be taken as the most familiar example. 



Fm 9.— Hiiirs 

 of Tiger 

 magnified. 



of Caterpillar 

 Moth, niiieh 



The hairs here emanate from small white tubercles placed 

 on a velvety black body ; in fi-ont and at the sides they are 

 rust-coloured, but on the rest of the body black tipped with 

 white. To the naked eye they seem to be simple, but the 

 microscope easily shows them to be finely feathered 

 (Fig. 9), with minute branches placed at considerable 

 intervals alternately along the 

 main stem. Their length is 

 so great that their effect is to 

 more than treble the insect's 

 apparent diameter : they are, 

 moreover, pre-eminently 

 elastic and recoil powerfully 

 when bent. When disturbed, 

 the catei-pillar rolls itself into 

 a ring, and the hairs, then 

 radiating in all directions, make it a most difficult object 

 to handle, their elasticity causing it to elude the grasp 

 again and again, so that it is impossible to seize it firmly. 

 Obviously, therefore, they are a valuable means of 

 protection. The habit of rolling into a ring is closely 

 connected with the hairiness of the larva, the one fact 

 indeed being the complement of the other ; as with the 

 hedgehog, the only vulnerable parts are by this means 

 protected, and it is easy to see that a smooth caterpillar 

 would gain little by the device. Hence we find that the habit 

 of rolling into a ring is very prevalent amongst densely 

 hairy caterpillars, though not universal ; moreover, it is a 

 habit not entirely confined to such larvfe, though much 

 commoner amongst them than in other groups. It is often 

 said that hairy caterpillars are avoided by birds ; but this 

 again is not universally true. That extremely shaggy 

 creature, the larva of the fox moth (Luxinfampa nilii), than 

 which it is scarcely possible to imagine anything hairier, 

 might, one would suppose, be a sufficiently disagreeable 

 mouthful ; yet the Rev. Harpur Crewe speaks of a bee- 

 eater, which one autumn visited the Scilly Islands, as 

 having lived principally upon these larvte ; it seized them 

 with its beak, and then, beating them on the ground till 

 they were dead, swallowed them whole. 



The distribution of the hairs varies very much in 

 different species. When they are fine and collected m 

 closely-compacted tufts along the back, like a row of 

 shaving brushes cut oft' Hat at the top, they form what 

 are called "tussocks" (Fig. 10). The most beautiful 

 example of this is the caterpillar of 

 the pale tussock moth {Ihisychii-n 

 jiuilihiDiihi), an insect of a very pale 

 and delicate green colour, with 

 velvety black crescentic bands at the 

 junctions of the central segments. 

 These black patches are not seen 

 under ordinary circumstances, being 

 concealed by the overlapping of the 

 segments, but they are suddenly 

 revealed when the insect bends its 

 its terrifying attitude, and more distinctly 

 adopts its final refuge and rolls into 

 the back are four large dense tussocks 

 yellow colour, in startling contrast to 

 them, which by the effect 

 look more cuusiiicuous and 



Fig. jo.— Central 

 segments of body 

 of Caterpillar 

 witli tussoeks. 



head under in 



still when it 



a rmg. On 



of a bright 



the l)lack bamls between 



of irradiation make them 



larger than they really are ;■ at the hinder end, in the 

 position of a caudal horn, is a sort of tail consisting of a 

 brush of rose-coloured hairs. This lovely caterpillar, one 

 of the most exquisite of J5ritish species in the delicacy and 

 purity of its tints, is common in most places, and may be 

 found in the summer feeding on a variety of trees ; to the 

 country folk it is known as the *' hop-dog." Tlie hairs of 



