338 



MUSEUM OF ANIMATED NATURE. 



I Insects. 



In the common hotise-fly the mouth h elongated || 

 into a flexible proboscis, terminating in fleshy 

 ■ucKmg hps, and this proboscis when not in use is 

 folded under the head ; in Tabanus, the Horse-fly, 

 the proboscis is formidably armed with knives or 

 lancets lor making an incision into the skin ; they 

 are five in number, the upper pair representinj; the 

 mandibles, the lower the maxill*, and the middle 

 one the tongue. Their sheath represents the labium. 

 The keen and long sucker of the gnat is repre- 

 sented at Fig. 3300 : a, the sucker in its sheath : b, 

 half of the sheath removed to show the piercing 

 instrument ; c, the whole separated to show the dis- 

 tinct parts ; d, the serrated point of one of the cut- 

 ting blades. The sheath is flexible and of use in 

 supporting the cutting instruments while they pierce 

 the skin. At Fig. 3361 is displayed the manner in 

 which the gnat applies its instruments to the skin : 

 they exemplify the use of the sheath, the extremity 

 of which is introduced into the wound, which is of 

 considerable depth, and, in consequence of some 

 poisonous secretion instilled into it, produces pain, 

 inflammation, and swelling. In many countries 

 gnats and mosquitoes are serious pests ; they make 

 their attacks not in armies of thousands, but in 

 clouds of countless myriads, and the destruction of 

 whole hosts only makes room for the sanguinary as- 

 saults of others. No dress can prevent their attack ; 

 Humboldt assures us that " between the little har- 

 bour of Higuerote and the mouth of the Rio Unare, 

 the wretched inhabitants are accustomed to stretch 

 themselves on the ground and pass the night buried 

 in the sand three or four inches deep, exposing only 

 the head, which they cover with a handkerchief." 



Fig. 3362 represents the male gnat ; a, the fe- 

 ■ male gnat (culex pipiens) magnified. 



Tig. 33G3 shows the sucker of a distinct species, 

 the Cleg (Haematopota pulvialis). a, the insect of 

 the natural size ; b, part of the head magnified ; 

 c, the same still more magnified, showing the eye 

 with its facets, the short antennae, and the sucker 

 unsheathed ; d, the lancets of the sucker separated 

 to show their form. 



By way of concluding our observations on the 

 mouths of insects, we refer to the subjoined illus- 

 trations. 



Fig. 3364 represents the head of the humble-bee, 

 beetle, and hive-bee — a a, the mandibles ; b b, the 

 roaxillee ; c c, the maxillary palpi ; d d, the labium ; 

 e e, labial palpi ; /, the tongue ; g, the articulation 

 of the head to the thorax. 



Fig. 3365 shows the so-called proboscis of the 

 bee, compared with the true proboscis of the butter- 

 fly. A, the proboscis of the bee ; a, the tongue for 

 hcking up honey; B, the head of the butterfly; a, 

 the compound eye ; 6, the proboscis partly unlolded ; 

 c and d, a portion of the tubular proboscis highly 

 magnified. 



We may now say a few words respecting the thorax 

 of insects, with which the limbs and wings are con- 

 nected. Jhe thorax consists of three segments 

 consolidated together, respectively named Prothorax, 

 Mesothorax, and Metathorax ; these terms indeed 

 rather apply to the upper than the under surface, 

 for the under part of the prothorax is called pro- 

 sternum; of the mesothorax, mesosternum ; and of 

 the metathorax, metasternum ; but this seems to be 

 carrying nomenclature too far. The prothorax 

 carries the first pair of legs; the mesothorax the 

 second pair, and the first pair of wings, or in their 

 stead the wing-cases (elytra) ; the metathorax 

 supports the third pair of legs, and the second pair 

 of wings. 



The number of segments in the abdomen is nine. 

 Fig. 3366 represents the larva of an insect, showing 

 the three segments of the thorax, and the nine seg- 

 ments of the abdomen— a, the thorax ; 6, the abdo- 

 men. Fig. 3367 displays the parts of the thorax of 

 a water-beetle, Dyticus margmalis : A, the under 

 side of the prothorax ; B, the upper side of the 

 mesothorax, called also mesonotum ; a, the scutel- 

 lum ; b b, the basal portions of the elytra : C, 

 posterior view of the same ; c, one of the middle 

 pair of legs: D, under side of the metathorax. 



Fig. 3368 represents the upper surface of the 

 thorax of the hornet. 1, prothorax ; 2, mesothorax ; 

 3, metathorax ; 1, a, scutellum ; 2, a, scutum ; 2, b, 

 squamula ; 2, c, scutellum ; 3, a, praescutum ; 3, b, 

 scutellum ; 3, c, postscutellum. 



Fig. 3369, the side view of the thorax of the 

 hornet. The figures and letters refer to the same 

 parts as in the preceding, to which may be added 

 1, b, praescutum and scutum; ), c, situation of 

 anterior pair of legs ; 2, d, sternum ; 2, e, situation of 

 middle pair of legs; 2,/, situation of anterior pair 

 of wings ; 3, d, metasternum ; 3, e, situation of pos- 

 terior pair of wings ; 3,/, insertion of posterior pair 

 of legs ; 4, commencement of abdomen. 



With respect to the limbs of injects, it may be 

 remarked that, as in Mammalia, they are constructed 

 for vei-y various uses, as running, leaping, burrowing, 

 swimming, &c., and consequently are variously 

 modified in detail. 



Referring to Fig. 3370, we may observe that they 

 are divided into five prin-'ipal parts : — The coxa, or 

 hip, A and C, a, which is the first joint or that 

 next to the body. The trochanter, A, B, and C— 

 b; the femur or thigh, c; the tibia or shank, rf; and 

 lastly the tarsus or loot, e, never composed of more | 

 than five joints, and often ending in two hooked : 

 claws, A, g, called unguiciili. The apex of the '• 

 tibia is often furnished with two spines called cal- 

 carea, A and B, /. To this we may add that A 

 represents a limb formed for running : B, a paddle- 

 shaped limb for swimming: C, a limb suited for 

 burrowing: D, a limb endowed with the power 

 of leaping, the thigh being voluminous and mus- 

 cular. 



In some insects, as the Crane-fly, or Long-legs 

 (Tipula oleracea), the limbs are extremely long, 

 slender, and oscillating, enabling the animal to 

 walk amidst the grass elevated as if on stilts : indeed 

 insects thus borne up and kept free from the dew, 

 may be called grass-waders. Many of the plant- 

 bugs have extremefy long limbs on which they 

 stalk along in a series of jerking movements. Fig. 

 3371 shows two insects of this tribe— a, Ploiaria 

 vagabunda, and b, Neides elegans. 



No one can have failed to observe how flies and 

 other dipterous insects walk up the glass of a win- 

 dow, or traverse the ceiling of a room. If we 

 examine the feet of a fly we shall find them fur- 

 nished under the last tarsal joint with two palmated 

 discs, which act as suckers, being each closely 

 adpressed to the surface. Besides these suckers 

 they have also hooks which enable them to cling 

 where rugosities afford the facility. In this appa- 

 ratus we are reminded of the Gecko lizard. The 

 suckers of the fly are concave underneath, and when 

 in action, are separated from each other and ex- 

 panded like the terminal sucker of a leech, the air 

 being sufficiently expelled beneath, so as to induce 

 a degree of atmospheric pressure sufficient to keep 

 the insect from fallmg. The suckers are margined 

 with minute serrations and covered with exquisitely 

 minute down. 



Fig. 3372 represents the foot of the common 

 Bluebottle-fly magnified six thousand four hundred 

 times. A, a view of the under surface of the 

 suckers, seen expanded when the insect is walking 

 against gravity ; B, a lateral view. 



The Fever-fly, Bibio (Tipula) febrilis, has three of 

 these suckers. See Fig. 3373— A, the under sur- 

 face ; B, a lateral view. 



Suckers, however, are not confined to the limbs 

 of climbing insects. We find them in the first and 

 middle pair of limbs of the males of the Dyticus 

 marginalis, or water-beetle. In the anterior legs the 

 three last joints of the tarsus are so dilated as to 

 form a broad circular palette covered on its under 

 surface with numerous suckers, of which one ex- 

 ceeds the rest in magnitude. The middle pair of 

 limbs have the tarsi furnished with a number of 

 small suckers, forming together an elongated cluster. 

 The male of this beetle may be known at a glance 

 by the smooth elytra ; in the female they are fur- 

 rowed. 



In the Blatta, Phasma, and Mantis, the limbs are 

 provided with foot-cushions variously arranged, 

 which appear to act as suckers. In the genera 

 Locusta and Acridiura, De Geer found a true claw- 

 sucker, as well as tarsal cushions, but the crickets 

 (Giyllus) have neither suckers nor cushions. 



The hind limbs of the Dyticus are, as we have 

 seen, adapted as swimming paddies, by means of 

 which the beetle ploughs its way through the water 

 with great vigour. The form is oval and depressed, 

 and its horny integuments are lubricated by some 

 subtle oleaginous fluid which effectually repels the 

 water. The coxie or haunches are not free, but 

 fixed immovably, and are greatly developed for 

 containing the voluminous muscles required to work 

 the paddles. Their fixedness adds to the precision 

 and vigour of the movements of these limbs, which 

 are parallel to the axis of the body. The Water- 

 boatman, Notonecta glauca, the rapid Whirwig 

 (Gyiiuus natator), the Water bug (Gerris lacustiis), 

 the Watei'-measuier (Hydrometra stagnorum), are 

 familiar examples of aquatic insects. 



Among insects formed for leaping we may in- 

 stance that little disturber of repose, the flea (Pulex 

 irritans), the grasshopper, the tree-hopper (cicada), 

 the cricket, &c. Aristophanes, by way of ridiculing 

 Socrates (.Nubes), represents him as having mea- 

 sured the leap of a flea. Since the days of Socrates 

 many philosophers have brought themselves within 

 the lash of the satiric Greek poet, and have mea- 

 sured the leap both of this and other insects. The 

 flea will propel itself to a distance measuring two 

 hundred times the length of its own body ; and a 

 locust will do the same, but the latter vibrates its 

 wings by way of aiding itself The leap of a horse, 

 at the same comparative ratio as that of tho wingless 

 flea, which is eft'ected by one muscular effort, would 

 be nearly fifteen thousand feet. Fig. 3374 repre- 

 sents the flea, magnified. 



Among leaping insects we may specify the Po- 

 dura aquatica, and the velvet spring-tail (Podura 

 holosericea). The latter, a minute insect, in a<lditioa 

 to its limbs, uses its tail as a sort of spring, and 

 propels itself to a great distance. Fig. 3375 shows 

 the velvet spring-tail in the leaping position, mag- 

 nified. 



We may here glance at the wings of insects, a 

 subject to which we must again sidvert when we 

 come to notice the transformations of these creatures, 

 and the mode in which they become developed into 

 maturity. These organs are two or four in number, 

 of a membranous and olten extremely delicate 

 texture, variously marked by nervures, which Jurine 

 has demonstrated to be airtubes continued from 

 the body. Delicate as are the wings, they are com- 

 posed of a double membranous tissue, between 

 which the nervures ramify, often so minutely (in 

 the Dragon-fly for instance) as to represent ex- 

 quisite lacework. They vary greatly in relative 

 extent and outline, and also in their position when at 

 rest: sometimes they are elevated ; sometimes they 

 cross each other, and sometimes are extended ; in 

 many tribes they are folded up, somewhat like the 

 wings of a bat, and hidden under wing-cases, or 

 elytra, of more or less rigid consistence. This 

 latter mode prevails throughout the coleoptera ; 

 which, instead of having anterior wings, have 

 these opaque portions under which the true 

 wings are folded when at rest. During flight 

 the elytra are extended, and give increase of 

 surface, without additional weight to the " shard- 

 borne beetle." In none of the coleoptera are 

 these elytra wanting, though in some species 

 the wings themselves are undeveloped. In many 

 insects, as butterflies and moths, the nervures 

 and tissues of the wings are hidden by minute 

 scales and plumes, which beneath a microscope 

 present very beautiful objects. These scales, which 

 to the naked eye appear like fine dust, are variously 

 arranged, but mostly in an imbricated manner, with 

 more or less regularity. They are inserted into the 

 membrane by a short footstalk or root but their 

 attachment is comparatively slight, whence they are 

 brushed off by a touch. Not only are they often 

 richly coloured, but they are marked with striae, 

 and often crossed by finer lines, and these striae, 

 by the reflection of the light at different angles, 

 produce varying tints of brilliant or metallic etful- 

 gence. Some idea of the almost endless variety of 

 form and markings which the scales of moths and 

 butterflies assume may be conceived when we state 

 that Lyonnet nearly fills .six quarto plates with 

 crowded delineations of those of one species, viz., 

 the Bombjx Cossus. The number of those scales 

 on the wings of a large butterfly almost defy 

 calculation. Leeuwenhoek counted upwards of 

 four hundred thousand on the wings of a silk moth, 

 and it is estimated that in one square inch of a 

 butterfly's wing the number of scales will amount 

 to one hundred thousand seven hundred and forty. 

 When these scales are rubbed off the wings will 

 be found to consist of an elastic transparent mem- 

 brane, exhibiting beneath a microscope indented 

 lines, according to the arrangement ol the scales. 

 In the scales of the wings of butterflies with iri- 

 descent colours, we are forcibly reminded of the scaly 

 feathersof the humming-bird. (Vol. i. p. 37!), note.) 

 We must not omit here to state that dipterous 

 or two winged insects, as the fly, the tipuia, &e., 

 have below the wings on each side a slender pe- 

 duncle terminated by a bulb or club ; these are 

 termed halteres, balancers, or poisers ; and they 

 vary in length in different species ; and from ex- 

 periments that have been often repeated it appears 

 that they steady the body during flight. Above 

 these balancers is a little scale or winglet (alula), 

 formed of two portions joined together at one of the 

 edges, and not unlike the two valves of a shell. 

 The use of these winglets is not very clear ; Scheler 

 found that if removed from a fly, the power of 

 buzzing ceased, and moreover that the faculty of 

 flight was destroyed, as much so as by the removal 

 of the balancers; these latter he conjectures to be 

 filled with air, and toserve as a sort of reservoir. 



In some dipterous insects, the balancers are 

 situated at the anterior part of the thorax. Latreille 

 terms them " pribalanciers." 



Referring to our pictorial specimens, Fig. 3376 

 represents a large beetle, with the elytra spread in 

 flight and the membranous v\ini;s displayed at full 

 stretch. Fig. 3377 represents the wings of several - 

 insects — a, the wing of a beetle ; ft, the wing of an 

 earwig ; c, the wing of the saw-fly ; d, the wing of 

 a crane fly ; e, the wing of a common fly ; /, the 

 wing of a midge (Psychoda.). 



Fig. 3378 represents a dipterous insect, Volucella 

 plumata, in which the winglets are very distinctly 

 seen. 



Fig. 3379 represents that well known fly called 

 father long-legs — A, a «, the poisers or balancers: 

 B, the poisers of another fly, seen at a a : C, the 

 poisers, seen at a a ; b b, the winglets. 



