182 



KNOWLEDGE 



[October 1, 1891. 



the male each foi-ms a curve, so that when closed they 

 constitute the honudaries of an open oval space. On the 

 inner edge, near the base, they are ornamented with small, 

 irreE;ular, tooth-like projections, and beyond these on each 

 side there is a solitary but much larger one, just where the 

 "legs" of the forceps begin to diverge. The forceps are 

 strong, stout organs, of a yellowish-brown colour, with the 

 teeth blackish ; they are highly polished, and exhibit in 

 different specimens considerable variety as to length and 

 degree of curvature. Sometimes, through accidents in 

 early life, they become twisted, or otherwise deformed. 

 Those of the female are simpler and less elegant. They do 

 not curve outwards when closed, but lie side by side as far 

 as the tip, where they cross one another slightly. In both 

 sexes they are habitually carried widely open, and pointing 

 obliquely upwards. The six legs are yellowish and almost 

 transparent, and are composed of the usual parts. 



Such is the external aspect of the common Earwig, from 

 which we may now pass to consider the structure and 

 manipulation of the wings, which are by far the most 

 beautiful part of the insect, and deserve special attention. 

 It is very seldom that the wings can be seen when the 

 Earwig is alive, for they are used chiefly by night, and one 

 can have no conception of their size, or of the beauty that 

 lies concealed under their covers, if one merely watches 

 the running insect ; indeed, it is difficult under such cir- 

 cumstances to believe even in their existence. To examine 

 the wings properly the Earwig must be killed ; this may 

 be done instantaneously, and without damage, by plunging 

 it into boiling water. Let it then be placed on blotting 

 paper to dry it, and afterwards laid full length upon some 

 hard surface. Then let the wing-covers be raised and 

 separated a little towards the right and left ; a neat little 

 package will thus be found under each, which, strange as 

 it may appear, is really a beautiful transparent wing, folded 

 up into extremely small compass. By dint of care and 

 patience it may be opened fold after fold till its full extent 

 is exposed, when it will be found to spread over an area 

 some seven or eight times as large as the cover under which 

 it was hid. 



The complete imfolding of the wing is a delicate opera- 

 tion, and must be managed methodically. The following 

 method will succeed very well if the directions are care- 

 fully attended to. The wing-cover having been removed 

 by raising it behind and then gently snipping it off in 

 front with a fine pair of scist-'ors, the folded wing lying 

 beneath may be carefully seized with forceps, lifted up and 

 snipped off' in the same way as the cover, or it may be 

 gently jralled away from its attachment. As it is too 

 small to be conveniently manipulated unless when fixed 

 to some support, a card should be provided, on which 

 may be placed with a small camel's-hair brush a very 

 little gum tragacanth, made by soaking a small piece of 

 the solid gum in water till it is of the consistency of 

 rather thick paste. The gum will very quickly dry if only 

 small quantities are used, and leave no trace behind ; it 

 should not be put on the card till the wing is ready to be 

 transferred to it. The wing packet may now be placed 

 gently on the gum with the uiipcr surface daivnu-anh. In 

 a few minutes the gum will be dry and the wing will thus 

 be fixed (Fig. 3, AJ. By aid of a needle it will now be 

 found that there are two layers of material folded upon 

 one another like the leaves of a book. One of the edges 

 will be observed to be straight, the other ciu'ved ; the 

 straight one is where the fold occurs. By aid of the 

 needle the flap may be lifted and turned over along this 

 hinge and pressed down on to another small supply of the 

 gum, which may be put on just in time to receive it. The 

 wing will now of course be twice as broad as before, and 



will present the appearance shown in Fig. 8, B. It will 

 now become evident that the part that has been turned 



6--' 



Fig. .3. Four stages in unfolding Earwig's left •wing. 

 The small letters represent the same parts in all the 

 figures. Magnified six diameters. 



back itself consists of two layers, bent upon one another 

 not in the same direction as before, but with the hinge 

 lying across the wing at its upper end. The uppermost 

 flap may easily be bent back across its hinge, when the 

 wing will appear as in Fig. 8, C. This last piece should 

 not be fastened down, but simply pressed back. Now 

 comes the most difficult part of all. The long smoky part 

 which occupies the whole of one side of the wing as it is 

 now displayed consists of a thin membrane strengthened 

 by leathery rays, and arranged in a number of longitudinal 

 folds, and the whole is bent back upon that part of the 

 wing that is attached to the card at the end opposite to 

 the position of the former hinge. It may be lifted at tl, 

 and as it is raised the membrane gradually opens itself out 

 in all directions. The outer edge may be gently pushed 

 back on to the card, on which another small supply of gum 

 has just been spread, and if care be taken to keep the 

 narrow dark triangle shown at l> (Fig. 8, D) in the same 

 line as the original outer boundary of the wing, the rest 

 wUl fall pretty easily into its place, and become neatly 

 spread out on the card. If it does not settle on the gum 

 quite smoothly the wrinkles may be got rid of by using the 

 needle as a sort of rolling pin, and rolling it out from the 

 stouter towards the weaker margin of the wdug. This 

 last operation requires care, as the membrane is very 

 easily torn. ^Ye now have the whole wing expanded with 

 its imder surface uppermost. It will keep any length of 

 time in this position. 



To imderstand why the wing always folds in precisely 

 the same way, attention should be directed to the mem- 

 branous part last exposed. From the joint b (Fig. 3, D) 

 nervures will be seen radiating hke the framework of a 

 fan. About half-way down its length, each dilates into a 

 minute sweUing, and as the indi^-idual rays diverge more 

 and more, other shorter ones are seen to spring up alter- 

 nately with them, passing outwards to the edge of the 

 wing, but not reaching the hinge aforesaid. These also 

 have each a similar but much larger swelling, the whole 

 set forming a row parallel to the hind margin of the wing 

 (d, Fig. 8, D). The membrane having been folded hke a fan 



