858 



MUSEUM OF ANIMATED NATURE. 



[Insects. 



till fairly got rid of annoy the animal exceedinitly : 

 havint^ attained the earth, they bury themselves, 

 assume the pupa condition, and in two months re- 

 appear aa perfect insects. 



rig. 3516 shows at one view by way of comparison 

 th« ovipositors of several insects already described. 

 We nave said that some insects are ovovivi- 

 parous, that is, they produce not ejr)?s, but living 

 yoimg. There is reason to believe this to be the 

 case with most of tlie aphides, and it is so with cer- 

 tain dipterous flies, as the chequered Blow-fly (Sar- 

 cophaga carnaria), and others. It would appear 

 that in these flies there is a large abdominal pouch 

 into which the eggs are transmitted, and where, 

 fostered by the \vaimth of the sun, the larvse be- 

 come disclosed, and ready to be deposited upon 

 putrescent animal mattere. Tlie eggs indeed of the 

 blow-flies which are oviparous, as the shining green 

 Ijlow-fly (Musca Cwsar, Linn.), and the common 

 bluebottle (Musca vomiloria, Linn.), very soon, 

 during the sultry weather of August, become grubs, 

 or, as they are often termed, maggots ; but in the 

 case of the chequered blow-fly, even this rapid 

 change is anticipated. 



This latter species is of a more slender figure than 

 the common bluebottle, and of a dark colour with 

 light stripes on the thorax. The female measures 

 about one third of an inch in length, and is pro- 

 vided with an abdominal sac for the reception 

 of the eggs, which are arranged in the form of a 

 roll of riband, and before exclusion assume the 

 larva state. Reaumur took the trouble to uncoil 

 this roll of compacted flies in embrj-o, and found it 

 to measure about two inches and a half in length, 

 and to contain about twenty thousand individuals. 

 After this statement we shall cease to wonder at the 

 suddenness with which large masses of decomposing 

 animal matter become as it were instinct with life, 

 heaving and moving with crawling myriads, ap- 

 pointed to act as the scavengers of nature. 



Fig. 3517 represents — A, the chequered blow-fly ; 

 B, tlie abdomen opened and magnified, showing the 

 coil of young larvse ; C, the coil of larvae partially 

 unwound. 



Another large gray blow-fly with red eyes, the 

 species not ascertained, was also found by Reaumur 

 to be ovoviviparous, but in this the larvse were less 

 numerous, and instead of being disposed so as to 

 form a spiral coil in the abdominal pouch, were 

 arranged longitudinally. Fig. 3518 represents this 

 fly at A, with the abdomen opened, showing the 

 young maggots ; and B, a peculiar respiratory appa- 

 ratus, something like a coronet, observed at the 

 caudal extremity of the maggots, and capable of 

 being shut down or raised at pleasure. 



We may now proceed from the eggs of insects to 

 consider more definitely the caterpillars or larvae of 

 insects, the changes they undergo, their modes of 

 life, their means of protection, and their general 

 habits and manners — subjects all of the highest in- 

 terest. 



We may premise by observing that the larvaa of 

 insects form two great divisions considered as to the 

 degree of their perfection, and indeed Burmeister 

 bases his system of entomology on this point, making 

 two primary groups, which he calls Ametabola, and 

 Metabola. Without laying any stress on Burmeister's 

 system or urging any objections against it, we may 

 observe that the first division consists of two orders 

 of insects, namely the Hemiptera, and Orthoptera, 

 including in the latter his Dictyoptera, viz. cock- 

 roaches ; and in these, the larva resembles the perfect 

 insect, ijut is destitute of wings; and the pupa, 

 instead of being motionless and torpid, runs about 

 and eats, and exhibits rudiments of wings: such 

 pupae are called nymphs, the former term being 

 applied to such as are torpid and limbless (the 

 terms chrysalis, from golden markings, and aurelia, 

 rather apply to the pupa of butterflies). Of the 

 ametabolous division the water boatman (Notonecta) 

 one of the Hemipte'Ja, the cricket, locust, grass- 

 hopper, &c., are examples. The second division 

 Metabola includes all the other orders. In these the 

 larva doesnot resemblethe perfect insect, and is a grub 

 or maggot without legs, or a caterpillar with legs. 

 The pupa, chrysalis, or aurelia is mostly limbless ex- 

 ternally, though the limbs may be often seen beneath 

 the case, and generally it is quiescent, for though it 

 can stir when irritated, it neither moves about nor 

 eats. 



At Fig. 3519 are represented in outline, four 

 larvae illustrative of our observations. A, an ameta- 

 bolous larva, or nymph of an Hemipterous insect 

 (Zelus); the others are metabolous; B, the larva 

 of a beetle or coleopterous insect (Telephorus) ; C, 

 the caterpillar of a lepidopterous insect (Sphinx) ; 

 D, the larva of a dipterous iasect, a gnat (Culex), 

 and of aquatic habits. 



Now as respects the non-locomotive powers, and 

 abstinence from food of metabolous pupee, there are 

 many exceptions ; for example, the aquatic larva of 

 the dragon fly (Xeuroptera) becomes a pupa with 

 limbs, which moves about and eats ; the same remark 



applies to the ephemertu and gnats, as far at least 

 as regards their locomotive powers. The fact is, 

 that so diversified arc the forms and characters of 

 larvae, and so various are the circumstances con- 

 nected with their metamorphosis, and so diversified 

 is their condition in the pupa state, from the cricket, 

 cockroach, or earwig, in which the pupa closely 

 resembles the perfect insect or imago, and enjoys 

 active existence, to the pupa of the silk-worm 

 shrouded in its cocoon, that it is difiicult to lay 

 down definitions to which all will conform. 



The structure and varieties however of larvae, their 

 peculiar changes, and the condition of the pupae, 

 will be best understood from the pictorial specimens 

 upon which we shall comment. 



All caterpillars, grubs, or larva;, on exclusion from 

 the egg are small ; they inciease rapidly in size, and 

 are voracious ; some carnivorous, others herbivorous. 

 Those of many coleoptera or beetles, and of Diptera 

 or two-winged flies, are destitute of eyes ; and in 

 others these organs ar.e largely developed. Many 

 have large and powerful jaws, as those of butterflies 

 and moths, though in the perfect insect the mouth 

 is haustellate. Some larvse are quite naked, others 

 are covered with hairs, and others again furnished 

 with spines. These appear to be intended to be a 

 protection against natural enemies, and indeed, if 

 Madame Merian be correct, those of the caterpillar 

 of Urania Leilus are as hard as wire. According to 

 Abbot, many caterpillars in America sling like a 

 nettle, and blister the hand when touched ; and 

 indeed the caterpillar of the gypsy moth of our own 

 country (Hypogymna dispar) is covered with slender 

 hairs that produce considerable irritation of the 

 skin. In many instances the long closely-set hairs 

 of caterpillars enable them to fall from considerable 

 elevations without injury ; like the hedgehog they roll 

 themselves up and drop down, the elasticity of their 

 hairs preventing the concussion of the body ; like 

 that quadruped, also, when alarmed or in danger, 

 they roll themselves up, and present a chevaux-de- 

 frise of slender bristles. This is exemplified in the 

 caterpillar of the tiger moth (Arctia Caja). Re- 

 ferring to Fig. 3520— a represents the hairy cater- 

 pillar of the tiger moth ; 6, the same rolled up for 

 defence ; c, the hair-tutted grub of the museum 

 beetle (anthrenus musaeorum) ; d, the same mag- 

 nified;/ and </, its hairs magnified; e, the tail of 

 the same magnified. This larva, the pest of cabinets, 

 being covered with tufts of diverging hair, is very 

 difiicult to lay hold of, for such is their smoothness 

 and elasticity that it slips between the fingers almost 

 like quicksilver. 



In certain butterflies (Vanessae) the caterpillars 

 are defended by hard sharp bristles or thorns, as 

 those of the " peacock's eye," which are of a dark 

 colour freckled with white, and feed in groups. 



Fig. 3321 represents three spiny caterpillars — 

 a a, a. caterpillar figured by Madame Merian ; b b, 

 the caterpillar of the peacock's eye (Vanessa lo) ; 



c, a supposed section with the spines magnified. 

 Fig. 3522 represents the tulted caterpillar of the 



drinker-moth (Odonistis potatoria), at a, in its early 

 stage ; at b, full grown ; c, the smooth caterpillar 

 of the angle-shades moth (Phoigophorameticulosa) ; 



d, the moth of the same. Naked as this caterpillar 

 is, it exists during the winter, in the heart of savoy 

 cabbages and other esculents of the garden, feeding 

 in open weather. In its last moult it changes from 

 a clear green to a yellowish brown. 



The larvae of many insects, as of the bees and 

 wasps (Hymenoptera), and of flies (Diptera), have 

 no limbs, but crawl by means of a vermiform action 

 of the body, or are passive. The larvae of a few 

 beetles, as of some of the weevil tribe (Rhycoptera), 

 are in the same condition. In larvse of the Lepi- 

 doptera, as butterflies and moths, there are two 

 kinds of legs : viz. true or persistent, and pro-legs 

 or temporary legs. With respect to the first, they 

 consist of three pairs attached respectively to the 

 three first segments of the body, the future thorax, 

 and are the rudiments of the legs of the perfect 

 insect ; they are horny and pointed. The pro-legs 

 are soft, short, and conical ; they vary in number in 

 different species. The caterpillar of the common 

 caltbage butterfly has five pairs; these leet are 

 furnished with a set of minute slender horny hooks 

 round a disc-like sole or sucker, by means of which 

 the animal is enabled to lay a very firm hold on the 

 leaves of plants or other objects, and also to move 

 along with tolerable dispatch. It is to be observed 

 that when five pairs of these limbs are present, 

 none are found on the fourth, fifth, tenth, or eleventh 

 segments, but a pair respectively on the sixth, 

 seventh, eighth, ninth, and twelfth segments, the 

 twellth segment being the last. In some cater- \ 

 pillars there are only two pairs of these limbs, one ! 

 pair on the last segment, one on the ninth ; such are I 

 the geometrical larvae, so called from their niea- ; 

 suring their progress in a very singular manner, : 

 namely by assuming the form of a pair of cal- I 

 lipers or rather of the Greek n (omega). At the l| 

 commencement of their movements they form an i' 



arch, bringing the anterior and posterior sestnents 

 of the body, on which are seated the true limbs, and 

 the pro-legs closely together. To take the first 

 step they stretch out the head to the full extent of 

 the body, secure themselves firmly, and then bring 

 up the rear, assuming the Q form again. Among 

 the more popular names for these caterpillars of a 

 tribe of moths, are loopers and surveyore. When 

 at rest they clasp with their pro-legs the twig on which 

 they are placed, and without using the true limbs 

 assume various attitudes at an angle with the twig, 

 of which many seem to be an oft'set or fork. They 

 I feed in the night, and are ready when disturbed to 

 drop down by means of a thread of silk from their 

 spinneret. Fig. 3523 shows the geometric cater- 

 pillars of the swallow-tail moth (Ourapteryx sam- 

 bucaria), in different attitudes on a twig of wliieh 

 they seem portions. 



■There are other variations in the number of the 

 pro-legs of caterpillars, but in none are the segments 

 mentioned as destitute ever furnished. 



Fig. .•J524 represents the leg and pro-leg of a 

 caterpillar magnified ; the pro-leg terminates in a 

 hooked acute claw ; the sucking disc of the pro-leg 

 is seen surrounded by the circle of little hooks. 



Many caterpillars, as is well known, spin silk : 

 some for cocoons for themselves in which to under- 

 go their last change, as the silkworm ; many weave 

 tents for themselves in which they dwell; others 

 nests and cells ; and others form threads by which to 

 suspend or secure themselves. 



Ihe spinneret of the caterpillar dift'ei-s in many 

 points from that of the spider. 



The spinneret of the caterpillar is between the 

 labium and two first limbs ; it appears in the form 

 of a protuberance or little tube, witn a single orifice 

 for the fluid silk, conveyed there by two fine ducts 

 which unite into one before their termination ; the 

 tube is said by Lyonnet to be composed of alternate 

 portions of horny and membranous substance, and is 

 cut at the end something like a writing pen. The 

 ducts are the continuations of two long slender and 

 tortuous sacculi, running internally down each side, 

 in which the silk is secreted in the ibrm of a gummy 

 fluid. The capacity and length of these sacculi 

 vary in proportion to the quantity of silk required, 

 and in the silk-worm these reservoii's are very exten- 

 sive, far more so than in the much larger caterpillar 

 of the Cossus ligniperda, or goat-moth. Fig. 3525 re- 

 presents the larva of the goat-moth, in which we may 

 observe "en passant "that the respiratory orifices 

 or stigmata along the side are very perceptible. 

 Fig. 3526 represents the internal organization of the 

 same caterpillar — A A, the sacculi in which the 

 gummy fluid, constituting the silk when drawn forth 

 ajid hardened, is secreted ; B, the silk tube, through 

 which the silk-gum is forced by a peristaltic musculai- 

 action ; C and D, the digestive apparatus. Fig. 

 3.i27 represents the labium of the caterpillar of the 

 Cossus — a, the silk tube or spinneret. Fig. 3528 

 exhibits a side view of the silk tube, and a section 

 of the silk tube magnified twenty-two thousand 

 times. 



Having noticed the silk apparatus with which so 

 many of the caterpillars of the Lepidoptem are 

 furnished, let us follow one of these creatures from 

 the egg, Fig. 3529, to the perfect insect, Fig. 3530 

 (Pontia Brassicffi). 



On its exclusion from the egg, we repeat, the 

 caterpillar is of very small size ; its growth, how- 

 ever, is as rapid as its appetite is voracious. Its 

 increase, however, is accompanied by successive 

 moults of skin, for its cuticle is not extensible, at 

 least beyond a certain point, if at all, and therefore, 

 like the armour of the lobster, must be repeatedly 

 changed. The change is thus effected : beneath 

 the original cuticle, or epidermis, which in due time 

 begins to be loosened, anew one is formed; a rent 

 takes place, from the swelling out of the animal, 

 down the back of the old skin, and this rent gradu- 

 ally increases till the caterpillar, with a brighter 

 epidermis, frees itself from its discarded weeds, and 

 appears of larger dimensions. During this process, 

 which is often repeated, the caterpillar is sluggish 

 and inactive, and refuses food ; but w hen the pro- 

 cess is over it recovers its former voracity. During 

 all this time the caterpillar is laying up an accu- 

 mulation of fat to serve the wants of the system 

 during the time of its torpid pupa state, which it is 

 now preparing for. Beneath the last cuticle as- 

 sumed, the vital energies of the system have deve- 

 loped wings, antenna.', a slender proboscis, and all 

 the parts of a perfect butterfly or moth that is to be. 

 This last cuticle, or epidermis, is, however, yet to be 

 cast oft', and another is formed to clothe the pupa, 

 or chrysalis, which in its turn is to be broken open 

 for the exit of the perfect insect. I>eviously, how- 

 ever, to the pupa state being assumed, it secures 

 itself by means of its silk in a positicn varying 

 according to the species. Suppose it merely sus- 

 pends itself by the tail ; in this case the first care of 

 the caterpillar is to cover the spot to which it is 

 about to suspend itself with successive layers of 



