620 



SUPPLEMENT 



that there are two sets of them, one consider- 

 ably shorter than the other. The longer scales 

 are inserted in the upper line, overlapping 

 each other, and the shorter, in the line beneath ; 

 by which means these extend to the middle 

 of the long scales, and have their extremities 

 covered by the next line. 



We shall notice only one other remarkable 

 appendage to some of the insect tribes, namely, 

 the sting ; the properties and mechanism of 

 which are worthy of consideration. The 

 sting of an insect, is a weapon with which 

 nature has armed it for purposes of self-defence ; 

 in no instance, we believe, is the sting resorted 

 to unless the insect has an instinctive sense of 

 danger, or has suffered provocation ; and, in. 

 deed, this may be inferred from the fact, that 

 the creature frequently inflicts fatal injury on 

 itself, when it strikes this weapon into its op- 

 ponent ; for from the barbs on the sides, it is 

 not able readily to disengage the sting, and 

 not unfrequently, by using desperate efforts to 

 obtain release, the insect tears out a portion of 

 its entrails. There are three distinct parts 

 connected with an insect's sting, each worthy 

 of attentive examination ; these are, the sheath, 

 the darts with their barbs, and the poison bag. 

 The following description of the sting of a bee, 

 extracted from Adam's Essays on the micro- 

 scope, will serve as a general exemplification. 



" The apparatus consists of two piercers 

 conducted in a sheath, groove, or director. 

 This groove is rather large at the base, but 

 terminates in a point ; it is affixed to the last 

 scale of the upper side of the abdomen by 

 thirteen thin scales, six on each side, and one 

 behind the rectum. These scales inclose the 

 rectum all round, and are attached to each 

 other by thin membranes, which allow of a 

 variety of motions ; three of them are, how- 

 ever, attached more closely to a round and 

 curved process, which comes from the basis 

 of the groove in which the sting lies, as also 

 to the curved arms of the sting, which spread 

 out externally. The two stings may be said 

 to begin with these two curved processes at 

 their union with the scales, and converging 

 towards the groove at its base, which they 

 enter, and then pass along to its point. The 

 two stings are notched or serrated towards 

 the point ; they can be thrust out a little way, 

 and drawn within it. These parts are all 

 moved by very strong muscles, which give 

 motions in almost all directions, but most par- 

 ticularly outwards. It is wonderful how deep 

 they will pierce solid bodies with this sting. 

 To pcrfoim this by mere force, two things are 

 necessary power of muscles and strength of 

 sting ; neither of which they seem to possess 

 in a sufficient degree. Mr J. Hunter thinks 

 that it cannot be by simple force, because the 

 least pressure bends the sting in any direction. 



It is probable that the serrated edges may as- 

 sist, by cutting their way like a saw. The ap- 

 paral us for the poison consists of two small ducts, 

 which are the glands that secrete the poison; 

 these lie in the abdomen among the air cells, 

 they soon, however, unite into one oblong bag ; 

 at the opposite end of which a duct passes out, 

 which runs towards the angle where the two 

 stings meet, and, entering between them, 

 forms a canal by the union of the two stings at 

 this point. From the serrated construction of 

 the stings, the bee can seldom disengage them, 

 and hence, when they pass into materials of 

 too strong a nature, the bee generally leaves 

 them behind, and often a part of the bowels 

 therewith." 



The poison bag is shown in the annexed 

 cut. 



We pass on to notice a few insects which 

 are purely microscopical, and require optical 

 aid to render their entire figure sufficiently 

 distinct for observation. And here, it must 

 be obvious, our remarks will necessarily be 

 of a very cursory description, and our illustra- 

 tive instances few ; for this one department 

 of our chapter would furnish, if carried out to 

 its full extent, a large and closely printed 

 volume. 



Amongst microscopical insects, the mono- 

 culus, or water flea, holds a distinguished 

 place. This insect belongs to the crab genus. 

 So numerous is it, in the summer months, that 

 the ponds appear tinged with red or green, 

 owing to the myriads of these minute crea- 

 tures upon their surface. When full grown, 

 some species of the water flea are about the 

 size of a common flea l This insect appears 

 to have but one eye, which, however, is com- 

 pound, and at the same time movable by 

 muscles in the manner of the human eye. The 

 young, perfectly formed, may sometimes be 

 seen within the parent. Mr Pritchard calls 



1 The Monoculus Polyphemus is the largest of all in- 

 sects, measuring four feet in length ; this, however, lies 

 beyond our province, which confines us to the rnint:te. 



