ISO 



♦ KNOW^LEDGE <► 



[JiLY 1, 18S9. 



Fif;. 4.--W1XG OF 

 Tiger-Beetle. 

 The dotted lines indi- 

 cate where the wing 

 is folded. 



in mind, and remembering that the insects are able instan- 

 taneously to start of}" through the air at apparently full speed, 

 and with equal suddenness to arrest 

 their course and alight on Iho ground, 

 we see at once further illustrations of 

 the extreme rapiditj' of movement of 

 which they are capable. In order to 

 commence flight, the wing-covers, or 

 elytra, have to be raised and spread 

 outwards, so as to liberate the wings, 

 which in their turn have to be un- 

 folded and expanded horizontally ; but 

 all these movements are performed so expeditiously that 

 the eye cannot follow them, and the insect seems in an 

 instant to rush into the full force of its headlong career. 

 The elytra are kept extended during flight, but do not them- 

 selves take part in the operation, being simply raised to 

 allow free play to the wings. The flight is not of long 

 duration, but the beetle simply dashes away a short distance 

 at break-neck speed, and then suddenly settle?, all trace of 

 the wings disappearing the instant it alights, if not the 

 moment before. 



There is a species called Cicindela sylvatlca, larger than 

 our common green tiger-bettle, of a deep violet^brown 

 colour, and found pretty commonly on the heaths of Surrey, 

 which takes somewhat longer flights than its green ally, 

 though its movements are conducted in a similar manner. 

 But on the other hand, our smallest species, C. yerinanica, 

 found in imt places, especially at Blackgang, in the Isle of 

 Wight, scarcely uses its wings at all, but employs itself in 

 nmniwj about over the marshy ground it frequents. Some 

 of the exotic Cicindelida'. are destitute of wings altogether, 

 and are perforce confined to the ground. A few species in 

 the tropics run about over the leaves of trees, apparently in 

 pursuit of other arboreal insects. Some, again, are found on 

 sandy seashores; belonging to this group is our own 

 C. hijhriaa, a brownish insect, with a curved creamy band 

 stretching partly across the elytra, and a few other creamy 

 markings. It is the same size as C. camjiestris, viz., about 

 half an inch long, and almost exactly the same shape. 

 These maritime species are often protectively coloured. 

 Bates mentions two tiger-beetles which he found on a sandy 

 shore in America, one of which was of a pallid hue like the 

 sand it ran upon, and could therefore readily escape de- 

 tection. The other, however, was of a brilliant copper 

 colour, and therefore exceedingly conspicuous ; nevertheless 

 it was as well protected as its obscure neighbour, for it 

 was possessed of a strong and offensive smell, a mixture of 

 that of putrid flesh and musk. The sand-coloured one, on 

 the other hand, being sufliciently protected by its colour, 

 was perfectly devoid of any such odour. 



It is now time to say a word about the earlier stages of 

 these insects. We will take for this purpose our common 

 green species, C. campestris. The larva; (tig. 5) are odd- 

 looking creatures, and may easily 

 be found in the situations frequented 

 by the perfect insects. A number 

 of circular holes will be observed 

 in the ground, which are the en- 

 trances of their cylindrical burrows ; 

 from these they may, with a little 

 care, be dug out. If a trowel be 

 inserted in the ground some six or 

 eight inches from one of these 

 openings, into which a straw or 

 stem of grass has been previously 

 passed, so as to render the direction 

 of the burrow evident even if the earth should fall in upon 

 it, the burrow may be traced to its end, descending verti- 



Fie. .5. — LiBVA OF 



'Jigbe-Beetle. 



TH0I!.\CIC 

 S E G .M E N T 

 OF TlGEIt- 



Beetle. 



cally to a depth of from six inches to a foot, according to 

 the nature of the soil and the age of the larva. 



Except in the jaws there is little resemblance between 

 the larva and the adult insect. It is a whitish fleshy grub, 

 with a broad, and what at first sight seems to be a decidedly 

 hluck head. A lens, however, brings out the fact that what 

 appears to be pure black is relieved by a da.sh of metallic 

 green. In this extremely inconspicuous and almost in- 

 visible green we have the sole indication of the biilliant 

 coloration destined to appear in the perfect insect ; no 

 doubt, however, the total absence of colour on the hinder 

 parts is largely connected with the subterranean habits of 

 the larva. The head is most strangely 

 shaped ; it is very hard, and its upper surface 

 is rough and concave, the latter a most excep- 

 tional circumstance. Beneath it Ls the exact 

 reverse of this, being highly polished and F10.6.— Head 

 extremely convex, and of a mahogany brown ^^^ First 

 colour (fig. 6). The segment immediately 

 behind the head is equally broad, semicii-cular 

 in shape, and covered above with a hard, 

 horny skin, which is usually much encrusted 

 with earth. The next two segments are similarly protected 

 above, but are considerably smaller. All the rest are quite 

 soft. The three shielded segments carry each a pair of legs^ 

 and are thus seen to correspond to the thorax 

 of the adult. For a larva of this kind, the ^^ 

 legs are much longer and thinner than might j^^^t^ 

 have been expected, a prophetic iudiciition of ?^ 

 the peculiarity that will characterLse the limbs \ 

 of the perfect beetle, and their apparent \ 

 length is again increased by the placing of pm 7 _ Dor- 

 their point of attachment to the body almost sal Hooks 

 at its sides instead of in the middle line, as is op Larva 

 usuallj' the case. The eighth segment after "^ Tiger- 

 the head is surmounted by a large hump, eetle. 

 which carries a pair of long hooks (fig. 7 ), which are movable, 

 and can be erected and depressed at pleasure. 



This brief sketch of the creature's form will havo 

 prepared us to understand how it makes its burrow and 

 catches its prey. The eggs are laid by the parent insect 

 where the larva will have no difliculty in selecting a spot 

 for .sinking its shaft. It begins excavating by nipping off 

 fragments of the soil with its jaws, which, instead of project- 

 ing straight forwards or sloping down from the head as is 

 almost universally the case, slant upwards, rising thus 

 above the level of the margins of the concave head-suiface. 

 As the burrow deepens, a difliculty arises as to the disposal 

 of the particles of soil removed. Then it is that the object 

 of the peculiar structure of the head becomes apparent. 

 While the animal is working with its bead down in its 

 burrow and its body projecting a 50ve, the fragments of sand 

 and earth, as removed by the upward sloping jaws, fall on 

 to the concave surface of the head, which is thrown back till 

 it is at right angles to the body, to i-eceive them as in a 

 shovel or saucer. A load having been thus obtained, the 

 grub backs out of its hole by means of its legs, carrying its 

 little saucerful of earth with it. These operations aie 

 repeated till the burrow is of sufficient depth, the animal 

 always working with its head downwards. When, how. 

 ever, the shaft is completed, the grub reverses its position 

 and drops into the hole with its head upwards. It can then 

 work its way up and down this vertical shaft, much in the 

 same way as the chimne3'-sweepers' boys used to climb 

 chimneys, using its legs and the hooks on the eighth 

 segment to give it purchase against the sides of the 

 burrow. 



In order to catch its prey it posts itself at the top of the 

 burrow, with its body in the shaft and its head and the semi- 



