June 1, 1889.] 



♦ KNOW^LEDGE ♦ 



157 



\^ AN ILLUSTRATED "^^ 



MAGAZINE OF SCIENCE 



SIMPLY WORDED — EXACTLY DESCRIBED 



LONDON: JUNE 1, 1889. 



CONTENTS. 



P 



Tiger-Beetles'.— I. By E. A. Butler 



The Nation's Purse. By Alex. B. MacDowall, M.A 



An Invertebrate Eye in the Vertebratii Skull. By W. Mawer, F.G.S 



Candles. By W. Mattieu Williams 



The Occurrence of Gold. By D. A. Louis, F.I C, F.C.S 



The Spectrum of the Orion Nebula 



Photograplis of Lightning. By W. Marriott and A. C. Ranyard 



Total Solar Eclipse of 1S89. January 1. By A. C. Eanyard 



Letters :— Prof. J. C. Adams, Dr. J. Westby-Gibson, U. W. Nic oU.«, W. 31 S. Mouck 



Notices of Books 



Notes 



The Face of the Sky for June. By Herbert Sadler, F.R.A.S 



Whist Column. By W. Montagu Gattie 



Chess Column 



TIGER-BEETLES. -I. 



By E. a. Buti.ek. 

 I>RY, i=andy bank, either entirely bare or 

 only scantily covered with vegetation, so 

 that there shall be, not a continuous carfjet 

 of verdure, but simply isolated tufts here 

 and there, with bare patches between — a 

 bright sunny morning in late spring or early 

 summer, when the sun's rays are pouring 

 down full upon that bank — these are the conditions of place 

 and time most favourable for observing tiger-beetles in the 

 full play of their activities. Let the observer take liis stand 

 at such a spot at such a time, and he will soon become 

 conscious of the rapid, lightning-like dash of some object 

 past him towards the bank, followed by an almost imper- 

 ceptible thud, but so quick is the movement and so instan- 

 taneous the phenomenon, that ho may need it repeated 

 several times before be can be quite sure of its reality, and 

 may even then require further scrutiny before he can dis- 

 cover its cause in the rapid movements of these really 

 bi'illiant, though not very easily detected insects. 



Tiger-beetles are among the most active and rapacious 

 examples of the whole order Coleoptent, and at the same time 

 some of the handsomest. Tliey constitute a distinct family 

 called tlie Clcindduhr,, and in systematic arrangements 

 stand first amongst the Geodci)haga, or carnivorous ground 

 beetles, which again are placed at the head of the whole 

 order. Thus they occupy in systematic zoology a position 

 amongst beetles analogous to that of eagles amongst birds. 

 The only genus represented in this country i^ tlie typical 

 one Cicindela, of which, again, wo possess only four species. 

 Kxotic forms are very numerous, and many of them are 

 exceedingly handsome in coloration as well as elegant in 

 form. In general structure tlie mnjorit}' of them are so 

 much alike that a description of the commonest English 



Fig. 1. — Cicindela 



Campestbis. The 



Common Tiger-Beetle. 



species will be sufficient to make clear the characteiistics 

 of the group as a whole. 



Our best-known tiger-beetle is called Ciciwlda cam- 

 pcsfris (fig. 1), and is an abundant insect in all sandy 

 places. Though so common, it is one 

 of the handsomest beetles we possess ; 

 above, it is of a bright green colour, 

 which, about the head and thorax, has 

 a little metallic gloss. The micro- 

 scope, however, effects a gi-eat im- 

 provement in its appearance ; the 

 surface is seen to exhibit a shagreened 

 texture, and in a good light all the 

 little irregularities glitter and sparkle 

 with gorgeous, gem-like tints. Few 

 sights, indeed, are more dazzling in 

 brilliancy than a low-power micro- 

 scopic view of the fore parts of one of 

 these insects, strongly illuminated as 

 an opaque object. The elytra, or wing 



covers, are rather flat on the back, with prominent shoulders, 

 and are marked with ten creamy spots, which, in diflferent 

 specimens, vary a good deal, both as to size and distinctness. 

 The colour of the back, too, is variable ; sometimes it is of 

 the most intense green, sometimes almost olive-green, and 

 occasionally black. Underneath the insect is, if possible, 

 handsomer than above ; the whole under surface is brilliantly 

 polished and of a deep metallic bluish-green, shot here and 

 there with coppery red. 



In the general aspect of these insects there are many 

 indications of the extraordinai-y rapacity and agility which 

 characterise them. The mouth-organs and legs naturally 

 exhibit the chief peculiarities. The latter are long and 

 slender, reminding one of the similarly modified organs in a 

 gazelle. They are perfect gems of coloration, for which 

 reason they are frequently mounted as opaque microscopic 

 objects, when, for exquisite range of tints, they vie with 

 that favourite object the iridescent bail's of the sea-mouse. 

 Their coloration is hardly seen to advantage till they are 

 removed from the body, when the brilliant ruby red shading 

 into the characteristic green is easily observed. So slender 

 are they, however, and so small, in consequence, is the com- 

 pass into which their beauty is packed, that it is quite un- 

 perceived by the naked eye unless they are examined closely. 

 And this remark applies almost equally to all entomological 

 specimens ; the characteristic peculiarities are so minute, 

 even at the best of times, that a person csmnot be said 

 really to have seen what an insect is like without making a 

 close and detailed examination, which will often be the 

 means of correcting first impressions, formed after a mere 

 cursory glance. There is no lesson the entomologist 

 needs more carefully to remember than that close and 

 attentive examination is always necessjvry, even with the 

 most familiar objects, and whoever ignores this is sure to be 

 peipetually making mistakes. The amateur, especially, in 

 meeting with any insect new to him, should never rest satis- 

 fied till he has carefully applied at leiist 

 a hand lens to all parts of its exterior. 

 If the structure of the legs is in- 

 dicative of agility, even to a greater 

 extent is that of the mouth organs 

 suggestive of rapacity. The man- 

 dibles (fig. '2) or principal jaw must be, 

 at least to the lower creation, truly 

 terrible instruments. Curved, intensely 

 hard, shiirp - pointed, and strongly 



toothed, they give the beetle a most cruel and ferocious aspect, 

 as they project considenvbly in front of the head, and they .are 

 so largo that when closed they cross one another like the 



Fig. 2.— JIandiblb 

 Of Tiger-Beetle. 



