October I, 1891.1 



KNOWLEDGE 



181 



J^' AN ILLUSTRATED "^^ 



MAGAZINE OF SCIENCE 



SIMPLY WORDED— EXACTLY DESCRIBED 



LONDON: OCTOBER 1, 1891. 



CONTENTS. 



PAGE 



Earwigs.— I. By E. A. Butlee .. .. 181 



International Yachting. By Erhakd Bev.nun, F.K.Gr.S. 183 



Swimming Animals. By R. Lydekker, B.A.Cantab. ... 185 

 The Diamond Minss of South Africa. By Vaughan 



CoBNi.sH, B.Sc, F.t'.S. 186 



On the Distance and Structure of the Milky Way in 



Cygnus. By A. C. Banvard . ,188 



Letters :— A. M. Cleeke ; J. K. Goke ; S. E. Peal; A. C. 



HENUERSorr li)0 



On some Peculiarities of the Variable Stars. By J. E. 



Goke, F.K.A.S ll»:i 



The Perfumes of Antiquity. By .1. Cn. Sawkr, F.L.S. ... 195 

 The Face of the Sky for October. By Herbert 



Sadler, F.R.A.S 198 



Chess Column. By C. D. LococK, B.A.Oxon 199 



NOTICE. 



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 Cheques and Postal Orders should be made payable to 

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 scriptions, and other business matters should be addressed. 



EARWIGS.-I. 



By E. a. IkiTLER. 



Till'; family of British Earwigs is a small one, 

 numbering at present six species ; no more than 

 two of these, however, are common, and probably 

 most people know only one, which to them there- 

 fore ranks as the Earwig. This is the insect 

 whose scientific name i.s For/ieulti anrinilariii, the well- 

 known species which is to be found abundantly everywhere. 

 We will take this common and i-asily obtained insect as 

 the typo of the group, in the hope tliat oin- readers will 

 catcli one, and follow with us the outline of its form ; the 

 deviations of structure which the other species present will 



then be easily appreciated. The common Earwig is so 

 well known that only a few words will be necessary to add 

 accuracy of detail to the rough general idea of its shape 

 and structure that is already in everybody's mind. Ex- 

 clusive of the forceps at the end of the body, wliich vary 

 considerably in size, the common Earwig has a length of 

 about half an inch. It has a flat, rounded, reddish head, 

 carrying a pair of 15-jointed antenns, at the base of which, 

 but outside them, are the black, oval, compound eyes, 

 which lie flat and do not project from the head. No ocelli, 

 or simple eyes, are present. 



Behind the head is the thin, flattish, shield-like cover of 

 the first segment of the thorax, which projects at the sides as 

 a kind of flap, and behind laps over the fi'ont of the wing- 

 covers. It is dark brownish-black in the centre, with pale 

 yellowish borders. Behind this is a pair of pale yellowish- 

 brown wing-covers, or elytra, which are thin and flexible, 

 and lie flat on the back, but bend do^Ti at the sides like those 

 of the house-cricket ; when closed they exactly meet, with a 

 straight junction along the middle line. Their hinder 

 edge in reality forms almost a straight line across the 

 body, but at first sight this does not seem to be the case ; 

 they appear to have two projecting pieces in the middle of 

 this edge, which remind one of the shape of the two halves 

 of the cloven hoof of a cow, save that they are almost flat. 

 These, however, are not part of the wing-covers at all, as 

 may easily be proved by raising the latter with the point 

 of a needle, when these projections are seen to be in no 

 way attached to them ; they belong in fact to the wings, 

 which, except for this part, are entirely concealed under 

 the covers. The wings and their covers when closed, as 

 one usually sees them, are so short that they conceal little 

 more than the hinder part of the thorax, and thus leave 

 almost the whole of the abdomen exposed. 



The abdomen is by far the largest part of the insect, 

 being the longest, the widest, and the deepest, so that 

 when the Earwig walks the fore part of the body is elevated 

 a little on the legs, while tbe abdomen almost trails 

 along upon the ground (Fig. 1). Nine distinct segments 

 can be seen above 

 in . the abdomen 

 of the male, but 

 only seven in the 

 female ; they are 

 of a mahogany- 

 brown colour, more 

 or less tinged in 

 places with black. To the hindmost segment are 

 attached the forceps, by which feature alone Earwigs 



Fig. 1. I'o.«ition of Earwig whcu walking. 



Fig. 2. Forrops of Earwigs. — .\, male; B, female. 

 Shown ill the position they take up after death, 

 ilagnificd six diameters. 



can be distinguished from all other insects. They differ 

 considerably in shape in the two sexes (Fig. 2) ; in 



