ON MICROSCOPIC DISCOVERY. 



613 



examine it before the forementioned fluid is 

 dried up, when it will be" found to be the per- 

 t'ect insect with the members glued together ; 

 these, by degrees, acquire sufficient force to 

 break their covering, and disengage them- 

 selves from the bands which confine them. 

 While in this state, all the parts of the insect 

 may be traced out, though so folded and laid 

 together, that it cannot make use of them ; 

 nor is it expedient that it should, as they 

 merely pass through this state to be hardened 

 and strengthened." 



The exuviae or cast skins, of insects, in 

 their larva, pupa, or perfect state, form most in- 

 teresting microscopic objects. " \Ve find in 

 the exuviae of the caterpillar, the skull, the 

 jaws, and all the exterior parts, both scaly and 

 rnembranaceous, which compose its upper and 

 under lip, its antennae, palpi, and even those 

 crustaceous pieces within the head, which 

 serve as a iixed basis to a number of muscles ; 

 we further find the spiracula, the claws, and 

 sheaths of the interior limbs, and in general 

 all that is visible of the caterpillar." From 

 an attentive examination of the various exuviae 

 which are cast oft by insects in different stages 

 of their existence, we are led to consider them 

 a compound system of organized bodies, con- 

 tained one within another ; for we not only 

 find in the cast skins all the exterior charac- 

 ters of the insect, but even the coats of the 

 gullet, pulmonary tubes, tracheal vessels, &c. 

 Indeed, there is not in animated nature a 

 more incomprehensible phenomenon than the 

 faculty which insects possess of throwing off, 

 repeatedly, the first surface of their exterior 

 members and internal organs. The writer 

 was walking, some years since, on a warm 

 summer evening, along the banks of a river 

 in the south of England, when a number of 

 small ephemerae settled on his dress; he paid 

 particular attention to one that had alighted 

 on his arm, and witnessed, in the course of a 

 quarter of an hour, no few6r than five exuviae 

 thrown off by the insect. These moultings, 

 as they may be termed, appeared to be effected 

 with much effort and suffering : the body of 

 the insect swelled, and deepened in colour, 

 and seemed to be exerting great muscular 

 energy to detach the exuviae. Another change 

 of colour to dusky white, indicated the mo- 

 ment when the skin was about to be cast off ; 

 the insect appeared to emerge from it easily ; 

 and for an instant the rejected covering pre- 

 sented a perfect skeleton, but immediately 

 afterwards collapsed and shrivelled up. What 

 is very remarkable, the insect suffered no ap- 

 parent diminution of bulk from these repeated 

 skinnings, and at length flew off and joined 

 the countless swarrn that hovered about the 

 water, into which, after a very brief interval, 

 they would fall lifeless. 



The jmago, or fly state of insects, is the 

 ultimate development of their forms, and 

 usually exhibits structures which for beauty 

 and delicacy are the very antipodes of the 

 larvae whence they are derived. For instance, 

 the unsightly caterpillar, crawling painfully 

 from leaf to leaf, or gorging itself with gross 

 nutriment, is transformed into the butterfly, 

 that skims lightly over the earth, or mounts 

 with sylph-like wing into the very clouds ; 

 which feeds daintily, and sips only the purest, 

 nectar of the opening flowers. It was a most 

 happy thought of the early times to make the 

 butterfly an emblem of immortality ; it was, 

 however, reserved for latter ages to discover all 

 the pertinence and value of the type. By the 

 aid of the microscope we have ascertained, that 

 not only the ravenous jaws and the whole exterior 

 parts of the larva are thrown off, even to the 

 eyes themselves, but that the internal system, 

 the stomach, lungs and various organs, are all 

 exchanged for other organs, members, and fa- 

 culties, suited to that higher state of existence 

 to which the insect form is summoned. Surely 

 we may, with no irreverent fancy, admire this 

 lively emblem of the corruptible putting on 

 incorruption, and the mortal putting on im- 

 mortality. 



We proceed to notice the wonderful struc- 

 ture observable in the different parts and 

 members of insects. 



The antenna and palpi are fine slender 

 articulated horns, movable in nearly all direc- 

 tions, and constituting Tone of the distinguish, 

 ing characteristics of the insect tribes. The 

 antennae are beautiful and various in form, of 

 a delicate structure, and so minutely jointed 

 as to be instantaneously movable at the plea- 

 sure of the insect. They are situated on the 

 fore part of the head. The articulations differ 

 in shape, length and number, and vary greatly 

 in different species ; the antennas of the male 

 differ also from those of the female. The 

 greater number of insects have only two an- 

 tennae, but some few have four. Regular rows 

 of minute holes are said to have been discovered 

 in the antennae. Several insects cover their 

 eyes with them whilst they sleep. Many 

 conjectures have been formed regarding the 

 use of these appendages : some have con- 

 sidered them organs of smelling and hearing, 

 others have supposed them to be appropriated 

 to a delicate species of feeling. From the 

 use to which the creature applies them, we 

 are perhaps justified in considering them the 

 organs of touch and hearing. If any sudden 

 noise be made close by an insect provided 

 with antennas, the motion of these horns suf- 

 ficiently indicates that they are affected by the 

 vibrations of the air; and, indeed, it is rational 

 to suppose that their delicate structure and 

 articulations must convey a sensation of sound 



