870 



MUSEUM OF ANIMATED NATURE. 



[Insects. 



cartfi:! in the adjustment of the specific £;ravity of 

 their case to their powers, adding a little sand or 

 sravel to it if too light, a straw or a bit of rush if too 

 heavy. 



Wiien the caddis-worm is about to assume its 

 pupa state, it withdraws itself completely within its 

 caw or tenement, and then closes the orifice with a 

 gratingof silk, which hardens and remains insoluble. 

 This grating admits the water necessary for respira- 

 tion, but etfectually keeps out intruders, for the 

 threads of which it is made are strong, and cross 

 each other so ns to form a perforated plate. The 

 time of change having arrived, the pupa, which is 

 l\imished with hard and horny mandibles, which 

 are temporary and about to be lost, cuts through the 

 lilken grating and creeps forth ; it then swims by 

 the action of its hmbs to the surface, or adheres to 

 any object ; the skin splits, and the perfect insect 

 emerges. 



Fig. 3605 shows — A, the larva of a species of 

 Phryganca, magnilied ; B, the case inhabited by the 

 larva; C, the pupa, magnified; D, the perfect insect 

 with the wings e.xpanded ; E, the same with the 

 trings in the ordinary position when at rest. 



Fig. 3606 shows — a, the pupa of Phryganea; 

 c and d, the appearance presented by the grating of 

 silk with whicn the orifice of the case is closed up ; 

 b, the perfect insect. 



In some parts of the continent showers of Phry- 

 ganese resemble those of the Ephemerse, filling the 

 air for a considerable distance. They fly chiefly in 

 the evening. The wings are light and semi-trans- 

 parent, like gauze. M. Latreille retains these in- 

 sects in the order Neuroptera, but they constitute 

 the type of the order Trichoptera in the system of 

 Mes.sis. Kirby and Spence. 



The larva of the dragon-fly is aquatic, and the 

 perfect insect, on wide-spread wings, may often be 

 seen sweeping round ponds and lakes, or the slug- 

 gish parts of rivers, for the purpose of committing its 

 eggs to the fluid element, in which the young brood 

 are destined to live. 



The larva of the dragon-fly has six legs, and 

 creeps about the stems of aquatic plants in search 

 of prey. Its mode of progression, however, through 

 the water is very extraordinary. Appended to the 

 posterior extremity of the body are five leaf-like 

 processes, fringed with hairs, and capable of being 

 closed together or expanded at pleasure ; these sur- 

 round the orifice of a cavity furnished with strong 

 muscular walls. Into this cavity the larva takes in 

 a certain quantity of water, which it instantaneously 

 rejects with considerable force; repeating this action 

 it thus propels itself along by a quu'k series of jerks, 

 each ejcctive .stroke giving the impulse. 



The larva of the dragon-fly is as voracious in the 

 water as the perfect insect is in the air; it devours 

 other aquatic larva;, as those of the ephemerae, and 

 even tadpoles; and a prehensile apparatus of the 

 most curious construction is given to it in order to 

 enable it more securely to seize its prey. The an- 

 terior part of the head is covered by a mask in three 

 parts, capable of being opened, and of closing, and 

 securing the prey, which is conveyed to the true 

 mouth. These three pieces may be likened to the 

 parts of a helmet covering the face, but the visor, 

 instead of being raised up, opens in the middle, 

 transversely, and the inner edges, where they meet, 

 are armed with sharp teeth. Each of these plates 

 then turns back, as it were, exposing the mouth. 

 The mask is, in fact, a strange modification of the 

 under lip, so inconspicuous in most insects, but in 

 this larva singularly developed and fashioned. 



Fig. 3607 represents — a, the larva of the drason- 

 fly ; b, the abdomen, laid open to show the respira- 

 tory vessels, or tracheae ; c, the pumping appara- 

 tus shut ; d, the same, open ; e, the head of the in- 

 sect. 



Fig. 3608 represents the mask of the larva of the 

 dragon fly, in four different states of opening and 

 shutting. 



The pupa difi^ers little from the larva, except in 

 displaying the encased rudiments of the wings. 



We have often witnessed the exclusion of the 

 perfect insect from the pupa, and a number of 

 aragon-flies and pupa cases are now before us, taken 

 on the banks of the Kennet, near Reading, where 

 thousands were then to be seen ; some yet in the 

 pupa state, others emerging from the pupa-case, 

 and others, with wings still wet and cmmbled, wait- 

 ing the moment of their full invigoration. When 

 the time for the disclosure of the perfect insect ap- 

 proaches, it leaves the water, and, crawling up the 

 bank, ascends a slalk of grass, or any other plant, 

 and there clings firmly with sharp claws. In a 

 short time, owing to internal pressure, the back of 

 the thorax splits longitudinally, and as regularly as 

 if a sharp in.->trument had made the incision, and the 

 head and thorax of the perfect insect make their 

 appearance ; in a little time it begins to rise more 

 completely, and to draw its legs out of those of the 

 pupa, as out of cast-off-boots ; afterwards the whole 

 body is extricated. There by the side of its slough, 



as if exhausted and feeble, the dragon fly rests : its 

 wings are small, crumpled , and powerless ; and it 

 is inanimate and without the means of escape. In 

 a short time, however, the body elongates, the wings 

 gradually expand ; it begins to vibrate them as if 

 to try their strength ; suddenly it rises and wheels in 

 rapid flight through the sunny air. On looking at 

 the pupa-case, we find the fissure has so nicely closed 

 that It is only by looking attentively that it can be dis- 

 covered ; the slough remains still cltngmg to the 

 stalk, and without examining it, one could scarcely 

 tell whether it was a living pupa or only the empty 

 case. 



Fig. 3600 exhibits the changes described : A, the 

 dragon-fly beginning to escape from the pupa; a, 

 the fly ; b, the pupa-case ; B, the process further 

 advanced ; c, the fly ; d, the pupa-case; C, the fly 

 nearly free, and forming an arch while it extricates 

 the body ; e, the fly ; /, the pupa-case ; D, the 

 dragon-tiy with the wings in a great measure 

 developed. Fig. 3610 represents the perfect 

 insect. 



The Gnat tribe (Culex) and many of the Tipulae 

 are aquatic during their incomplete stages. 



The larva of one species of the latter, the Chirono- 

 mus plumosus, is abundant in ponds, and even rain- 

 water tubs. We have seen the water teem with 

 these creatures, which are like little red wriggling 

 jointed worms, perpetually swimming about. The 

 caudal extremity is furnished with several small 

 appendages, regarded as an organ of aquatic respira- 

 tion. In the pupa state these appendages are 

 replaced by a tull of fine bristles, and a coronet is 

 produced on the head like a five-starred ray of 

 plumes, and a double envelope projects from each 

 side of the thorax, enclosing the limbs. 



The pupae undergo their change on the surface of 

 the water with the thora.\ above it, and in allusion 

 to this fact Messrs. Kiiby and Spence ask, " How 

 can a pupa of greater specific gravity than the 

 water remain suspended without motion at its sur- 

 face, and how can its thorax, which is its heaviest 

 part, be kept uppermost i'" The solution given is, 

 that the middle of the thorax is oleaginous, and re- 

 pels the water, and that as soon as the pupa by its 

 exertions has forced this part above the surface, the 

 water retreats from it, and the attraction of the air 

 acting on the dry part issufficient to counter-balance 

 the body's gravity, as a needle being very dry will 

 float on water from the same cause. 



May it not, however, we would ask, be that pre- 

 viously to the last change the body, by the expan- 

 sion of the internal parts, becomes really so light as 

 to remain floating? This is a mere suggestion. 



Fig. 3611 shows the changes of the Chironomus 

 plumosus ; a, the gnat, with its plumed antennae ; 

 b, the larva of the same, called the blood-worm ; 

 d and c, pupae of the same, magnified. 



We have previously alluded to the egg-raft of the 

 giiat (Culex pipiens). The larva is aquatic, but 

 breathes air ; it is of strange figure, and its move- 

 ments with the head downwards are singularly 

 quick and active. As atmospheric air is necessary 

 for its existence, there is an express organization for 

 obtaining a due supply. On looking at these larvae 

 in a quiescent state, we find them invariably at the 

 surface of the water, with the head hanging down 

 and the tail above. Now on examining one through 

 a lens we find it to consist of a long slender body, 

 and a large thorax, with a strange-looking head, 

 scarcely less in magnitude. The tail appears bifid, 

 but in reality it gives off', before its termination, a 

 breathing-tube. At the end of this tube is a circlet 

 of moveable hair-like appendages, so arranged as 

 to sustain the creature at the top of the water, and 

 thus serve as a float. The respiratory tube, which 

 is just raised above the surface of the water, is con- 

 nected with the internal air-vessels, and is thus 

 adapted for its assigned use. 



The segments of the body and the thorax are fur- 

 nished with radiatory pencils of fine hairs, and on 

 the head are two cilia, by the movements of which 

 food is brought to the mouth. It is from the vibra- 

 tile action of the body that the animal swims about, 

 and the fine hairs with which it is furnished seem to 

 coittribute to render it buoyant, for when its actions 

 cease it begins to ascend to the surface without any 

 visible effort. 



Several times before assuming the pupa state 

 this larva moults its skin, but when this state is 

 attained the creature would scarcely be recognised 

 as the same. The thorax and head appear to be 

 no longer divided, but form one continuous portion , 

 within which the outlines of the perfect insect may 

 be detected. The elongated tail-like body is still 

 used as an organ of locomotion, and the pupa floats 

 at the surface, but not in its former attitude. It 

 now swims with the back of the thorax uppermcst, 

 and a remarkable change has taken place in its re- 

 spiratory apparatus; the caudal tube has become 

 obliterated, and in its place two short tubes rise 

 from the back of the thorax, so as to have their 

 orifices just above the surface. These alterations 



prepare the way for the escape of the insect from 

 its pristine element into the air. 



Floating, as we have said, with the back ol' the 

 thorax uppermost, the pupa, as the important crisis 

 draws near, becomes still more buoyant, till its 

 back rises above the water. The membranous in- 

 tegument now begins to dry, it then splits longi- 

 tudinally, and, gradually expanding, forms a boat, 

 in which rests, unwetted and secure, the perfect 

 insect. It floats on a coracle of its own pupa- 

 case, which it leaves behind as it rises on flutter- 

 ! ing wings to join the mazy dance of its kindred 

 myriads. 



Fig. 3612 represents the larva of the common 

 gnat (Culex pipiens) floating in water : a a, the 

 head and body; b, the caudal respiratory tube; 

 c, the larva, of the natural size. Fig. 3613 shows 

 several of the larvae and pupae in a glass vessel of 

 wafer. 



Fig. 3614 shows at c, the pupa of the gnat, front 

 view ; d, a lateral view of the same, with its dorsal 

 tubes ; a, is a species of Tipula, and b its pupa, the 

 respiratory tube of which is many times larger than 

 the body, and as fine as a hair ; its extremity always 

 remains above the surface of the water, for the pur- 

 pose of carrying on respiration. Fig. 3615 shows 

 the gnat escaping from its floating pupa-case. 



There is a two-winged fly, called by Goedart the 

 Chameleon-fly (Stratiomys Chameleon), the larva of 

 which is aquatic, and is at the same time beautifully 

 provided with the means of atmospheric respiration. 

 The terminal ring of the body is considerably elon- 

 gated, and the respiratory orifice is frmged around 

 with about thirty feathered filaments, forming a 

 beautiful star. These constitute a float, and repel 

 the water, in which the creature rests suspended 

 with the liead downwards: when it wishes to de- 

 scend, it brings the filaments together, enclosing 

 within them a bubble of air for respiration, under 

 the water, and the bubble appears like a brilliant 

 pellet of burnished silver. 



When the period of transformation into the pupa 

 draws near, this larva forsakes the water, and creeps 

 up the hank, or on the leaf of some aquatic plant, 

 with only a portion of its tail submerged. It now 

 ! becomes motionless, and the embiyo fly enclosed 

 begins to contract within its case, while its wings 

 and limbs gradually develop. Into the vacant 

 space around it, and which it previously occupied, 

 the air enters for the supply of the insect, which 

 soon opens a sort of lid at the top of the dry co- 

 nical pupa-case, and emerges. Fig. 3016 represents 

 the aquatic larva of the Chameleon-fly with its 

 caudal apparatus expanded. 



Fig. 3617 represents — A, the pupa of the chame- 

 leon-fly viith the lid of the pupa-case raised ; B, the 

 same, magnified to show the contracted embryo of 

 the fly in its case, which it does not even nearly fill : 

 C, the embryo fly, magnified ; a a, antennae ; b b, the 

 eyes ; c, the sucker ; d d, first pair of legs; e e, se- 

 cond pair ; ff, wings folded up ; g, h, i", rings of 

 body; k k, stigmata, or respiratory orifices. 



The larva of a Tipulidan gnat fCorethra plumi- 

 cornis) is remarkable for its crystalline tran>parency, 

 and from this and its minute size it is not very easy 

 to discover. It is less than a quarter of a;i inch in 

 length, and is furnished with horny jointed man- 

 dibles, capable of being united into one pointed 

 borer. The tail is furnished with a pencil of plumed 

 bristles, which may perhaps serve tor aquatic respira- 

 tion, and also as organs of locomotion. As this 

 transparent larva approaches the pupa staire, two 

 kidney-shaped brown bodies become visible within 

 the first ring succeeding the head, and two smaller 

 in the fourth ring from the last. The first, perhaps, 

 enclose two singular horns, which appear on the 

 pupa, and the latter two tail-paddles. The transi- 

 tion from the larva info the pupa state, according to 

 Reaumur, is by a change of skin, and the antennae 

 of the perfect insect are enclosed in the horn-like 

 appendages of the latter. The pupa is very lively, 

 jerking about, and generally keeps close to the sur- 

 face of the wafer, above which its horns project. 



Fig. .3618 shows — a n, the larva of Corethra plu- 

 micornis, magnified ; 6, the mandibles and palpi ; 

 c, the respiratory appendages ; d, the pupa, mag- 

 nified ; e, the pupa, natural size ; f, the larva, natural 

 size ; g, the female fly ; /(, the male. 



All are acquainted with what are termed rat-tailed 

 maggots, common in filthy drains, in oozy mud, and 

 similar places. It is the larva of a species of two- 

 winged fly, very like abee in appearance, the Helophi- 

 lus pendulus, and its singular tail is an apparatus for 

 breathing admirably adapted to its necessities. This 

 instrument consists of an outer tube, within which 

 a much finer tube, capable of being extended to a 

 very great length, is retracted when not in use; 

 both are composed of fibrous rings, and are of 

 amazing extensibility. The contrivance for extend- 

 ing the inner tube appears to be very simple, and 

 yet extremely efficient : it receives at its ba.se two 

 flexible pijies, coiled uj) when at rest, which are 

 continued from the internal tracheae, or air-vessels, 



