Ado. 7, 1885.] 



♦ KNOWLEDGE ♦ 



rounding mountains. By contrast with tlie.se si 

 the floor looks lighter than it really is ; as they > 1 1 

 it seems to grow darker ; when they disappear nli^ 

 it looks darkest: 



the aftei 

 th, 





floor seems to tst-i li-hi li-iniK A ' i:. ' ' ■' i '.i<t 

 the floor gets brighter us iln' -1111 iim- h i.j in r ;i h-\ c iis 

 level, and darkens again as 1 lie mmi 'jrndually ncars the 

 horizon of Plato. 



The illusions aiicctin- iiu.t i.u arr too remarkable and 

 too numerous to be deah with ju'dperly in the small space 

 remaining to me here. I may perhaps consider them 

 hereafter in a separate short essay. 



OUR HOUSEHOLD INSECTS. 

 By E. a. Butleb. 



COLEOPTEEA (contuiued). 



WE conclude our notice of the family Tenelrionidw 

 with the creatures called "mealworms," which 

 are the larvfe of two species of beetles, Tenelrio 'inulitor 

 and T. obscurus. Both larvse and perfect insects are 

 found in granaries, flour-mills, and bakehouses, where 

 they sometimes do much damage to meal, bran, and 

 flour. The larvte are much more familiar objects than 

 the images, though probably the reverse is the case with 

 the rest of the family. They are tised as food for certain 

 singing-birds and other insectivorous creatures, and 

 hence are bred in large niimbers by bird-fanciers. This 

 may readily be done by keeping them in bran, when they 

 will propagate themselves freely. The word Tinehrio is 

 Latin for a night-walker, or lover of darkness, and so far 

 as the mere meaning is concerned, the name would be 

 just as applicable to the rest of the family as to the pre- 

 sent insects, the whole set being devotees of obscurity. 

 Molitor is Latin for a grinder of coi-n, and ohscuncs finds 

 its explanation in the dull appearance of the second 

 species. 



T. molitor (Fig. 1, A) is a narrow, parallel- sided 

 beetle, a little over half-an-iuch in length. Abnvp it is 

 almost black, the faintest possible tinge ..f a .laiL Im.mmi- 

 red preventing it from being quite s.. ; nr |rilia|s it 

 might be more correctly described as deep lnow n-r. d, so 

 deep as to appear almost black ; beneath ami in ilic l.'-s 

 the lighter colour is much more apiiareiit. I1 is sll- In ly 

 shiny, but only just sufficiently so to be nilrniHil I'roni 

 the utter dulncss and dinginess which eliaraeti rise its 

 relative T. ohscurus. Down the elytra run the inevitahh' 

 ])arallel furrows, sixteen in number, not deep, but dis- 

 tinct enough to form a little "set-ofi" to tlic otherwise 

 uninteresting appearance. The front of the head forms 

 a ridge, which, as in some other species previously 

 referred to, encroaches considerably on the eyes. The 



1. js ;ire rather short, and the antennas are inelegant, 

 ilii. k, and stumpy. Unlike Bla]}s, it is ftimished with 

 \' iiius, and therefore, of course, the elytra are not soldered 



1z'. obscurus is a trifle larger than T. molitor, perfectly 

 dull black above, without a trace of the red-brown tint, 

 which, however, appears again on the under side ; in 

 other respects it is almost the exact counterpart of its 

 slightly less inelegant congener. 



Such are the parents of our mealworms ; the 

 " worms " themselves are as different as can well be 

 imagined — long, narrow, cylindrical, caterpillar - like 

 creatures (Fig. 1 B), consisting of a head and twelve 

 similar and perfectly distinct segments. The colour is 

 pale yellow, shading ofi; into yellowish-brown towards 

 the head and tail. Each segment at its hinder edge 

 carries a rather broad band, and at its front edge an 

 exceedingly narrow one, of the darker coloiir, so that the 

 body is adorned with a series of double rings encircUng 

 it at intervals along its length. The last segment iis 

 rounded behind, and terminates on its upper surface in 

 either one or two small black curved hooks. The 

 head is furnished with a pair of not very large, but 

 nevertheless strong, dark brown jaws, which, in repose, 

 close in between the upper and lower lips, so that only 

 their outer edges are seen. There are also a pair of tiny 

 antennse. 



Under the three segments immediately succeeding the 

 head are three pairs of short legs, each terminating in & 

 sharp curved claw. By means of these the " worm " is 

 able to progress at a tolerably rapid rate, provided there 

 are sufiicient irregularities in the surface to afford foot- 

 hold to its tiny claws ; but if transferred to a polished 



the- h-i. ' ■ ■ — ^■li^^ • "' " ■ - .:./'-:- n'- -'y 



moved forward simultaneously, and the order of move- 

 ment, which is not always quite uniform, and is ex- 

 tremely difficult to follow, appears generally to be first 

 the front pair, then the third, and lastly the second. As 

 the insect walks along, that part of the bpdy immediately 

 over the legs is, of course, somewhat raised, but the head 

 is kept near the ground, so that it may feel its way with 

 vibrating antennas and palpi. When walking slowly, or 

 endeavouring to extricate itself from a difficult position, 

 it also makes use of a pair of fleshy tubercles underneath 

 the front part -f iIm iMm'nal segment, thereby either 

 helping the hi iiM ' i ' :> Imdyforwai-d, or acquiring 



leverage for 1I1. ; ; 11 of the legs. But when 



trottingbriskly a'.')^.; ill. :. , , ,aiis to be no necessity to 

 call these tubercles int.! |'!;'\. aii.l tlie hinder part of the 

 body therefore simply trails hrlph-sly (.verthe ground. 



When fully grown tlu' lar\a Is uraiay double as long as 

 the beetle it produces, but. what the luUer loses in length 

 it gains in breadth, as it is fully twice as broad as its 

 ancestral worm. Having spent some months in devour- 

 ing farinaceous substances, and changed its skin several 

 limes iluriiig that piridd, thr " \\c 1^1" mfrrs its penulti- 



,'''u',lin.''~'ll 'is now 'slinrirr an.l l,r..a,ha- ( Ki-. 1. C), no 



it throws oil its last skin, and appears ii fully -developed 

 winged beetle, at first soft and red, but destined soon to 



