170 



♦ KNOWLEDGE ♦ 



[Aug. 29, 1884. 



cannot be sufficiently sliown without the exhibition of the 

 entire apparatus. The limitations of space which make 

 these restrictions necessary, also compel the Council to 

 decline, unless iu exceptional circumstances, to receive 

 objects which have already been shown in either of the 

 recent exhibitions. 



The second division — music — will, of course, be aiTanged 

 on somewhat different principles. Here the object will be 

 to illustrate as completely and in as interesting a manner 

 as may be all that relates to the development of the 

 science and of the art of music. Examples of musical 

 instruments of a date not earlier than the commencement 

 of the present century, and any machinery, apparatus, or 

 appliances connected with their manufacture or their use, 

 will be admissible. And, further, without restriction of 

 date, contributions to an historic collection of musical 

 instruments, and paintings and engravings representing 

 musical subjects, are invited, and many, it is known, will 

 be forthcoming. 



Criticism at this early stage is practically out of the 

 Question, but the Council includes such a phalanx of good 

 men (Sir Frederick Bramwell, F.R.S., vice-president of the 

 Institute of Civil Engineers, Sir Frederick Abel, C.B., Mr. 

 I. Lowthian Bell, F.R.S., president of the Institute of 

 Mechanical Engineers, Colonel Sir Francis Bolton, Professor 

 Dewar, F.R.S., Sir George Grove, D.C.L, Mr. W. H. 

 Preece, F.R.S., Sir E. J. Reed, M.P., F.R S., Professor 

 Chandler Roberts, F.R.S., Dr. Stainer, Mr. R. E. Webster, 

 Q.C., &c.), that there will, I fancy, be little to iind fault 

 with. 



One thing is very certain, and that is, that the Exhi- 

 bition will be one from which excellent results may, and 

 most assuredly will, be looked for. The first division will 

 be divided into some thirty or thirty-one groups, and single 

 specimens of the objects mentioned in the prospectus 

 would in themselves constitute a show of no mean 

 proportions. We hope, naturally, for something more 

 than this. Practically, every branch of human in- 

 dustry is taken up — and, indeed, it is almost a 

 matter of impossibility to conceive how any one thing 

 could be regarded as outside the scope embraced by the 

 title. It follows that there will be whole multitudes who 

 will visit the Exhibition, and who will leave it minus that 

 benefit which they ought to derive. It will be the duty of 

 Knowledge to help its readers to grasp more truly the 

 lessons to be learned from what we have no doubt will be 

 a great and a highly interesting exhibition. Such exhibits 

 as may be likely to prove beneficial to the community will 

 be referred to, and described more or less fully, sight not 

 being lost of the fact that while many of our readers may 

 be able to view the objects themselves, many others, pos- 

 sibly the majority, will be debarred for various reasons from 

 ever visiting the Exhibition. 



THE ENTOMOLOGY OF A POND. 



By E. a. Butler. 



THE BOTTOM (continued). 



THE Eanatra linearis is a creature of three elements, 

 though, of course, its proper sphere is the water. It 

 can manage to progress on land better than most aquatic 

 insects, carrying its body high up on its stilt-like second 

 and third pairs of legs ; still, its movements are, at best, 

 but slow and awkward. It will also, sometimes, take to 

 the air, and on returning to its pond, finds occasionally a 

 little difficulty in re-entering the water, on account of its 



own slight specific gravity and the dryness <if its tail 

 filaments, so that quite a struggle is necessary beforo it js 

 completely immersed. It is a sluggish insect, and nill 

 often remain motionless amongst the pond weeds for a long 

 time together, only rising to the surface to breathe, and 

 this, as one might expsct in so inactive an insect, it needs 

 to do very infrequently. It makes its way through the 

 water, either by the help of aquatic plants, or by the 

 movements of its two hind pairs of legs ; but these are 

 worked somewhat peculiarly, the third pair being driven 

 backwards at the same time that the second are moved 

 forwards, and vice versd, all the movements being performed 

 in a leisurely manner. But when we come to the front 

 legs, the case is altogether different ; all the celerity of 

 which the insect is capable seems to be concentrated here. 

 Ranatra, indeed, is more of a living trap than a hunter, 

 lying in wait for, more frequently than pursuing, its prey, 

 which consists of other aquatic insects, especially the larva; 

 of Mayflies, and even small fishes. With fore-legs extended, 

 it patiently waits till some unwary and unsuspicious being, 

 on pleasure only bent, approaches within the charmed 

 circle guarded by those long-handled sickles, and then, with 

 a rapid and forcible stroke and with unerring aim, down 

 come the powerful limbs and seize the hapless pleasure- 

 seeker as between a pair of pincers. Dragged to the cruel 

 beak of its thirsty foe, its juices are gradually extracted, 

 and the grasp is not relaxed till the dregs have been 

 drained and nothing but the skin is left ; the useless pellicle 

 is then rejected and the lanky tyrant brings itself into 

 position for another attack. It is said sometimes to regale 

 itself on fish spawn, a proceeding which naturally excites 

 the ire of pisciculturists. It holds its prey with astonishing 

 tenacity, of which the following instance, recorded in the 

 " Entomologist," by Mr. A. G. Laker, may serve as an 

 example. He says : — " I placed some sticklebacks in the 

 glass with a Ranatra, when one of them, about an inch long, 

 was seized (the total length of the Ranatra, exclusive of 

 its anal filaments, being only eighteen lines), and, notwith- 

 standing the fish's repeated and vigorous striiggles, it was 

 held fast. I then took hold of the stickleback and raised 

 it out of the water ; the Ranatra, however, would not let 

 go, and was drawn out of the water with the fish. I 

 forcibly separated the two, replaced the insect, and imme- 

 diately afterwards the fish ; but the latter was again seized 

 in a very short time, and the insect continued its meal." 

 Ranatra is an exceedingly bold and fearless insect, mani- 

 festing surprising readiness to attack any foe, let its size be 

 what it may. In fact, under ordinary circumstances, there 

 are probably but few enemies that it has any need to fear. 

 It is the giant of the insect population of the pond, and can 

 hold its own against almost all comers. The great Dytisci 

 are probably the only insects of which it has any need to 

 stand in awe ; and tlipse, if hard pressed by hunger, woiild 

 probably have no hesitation in attacking it, and, protected 

 by the invulnerable nature of their chitinous armature, 

 would soon make mincemeat of the slim and long-legged 

 bug. The hard integument 6i beetles, however, does not 

 always bafile Ranatra, not even when it seems to offer an 

 insurmountable obstacle. There is a little oval, reddish - 

 brown beetle, Ili/phydriis ovatzts by name, about the size cf 

 a small pea, and not unlike a somewhat flattened one iu 

 shape, which is about as unmanageable a morsel as could 

 well fall to the lot of any insect ; but even this Ranatra 

 will not refuse, turning and twisting it about with its 

 pincers in vain efforts to find a soft spot in which to plungr; 

 its beak, till at last it lights upon the extremity of the 

 abdomen, as being a little less hard than the rest, and 

 manages to extract even thence at least enough nutriment 

 to whet its appetite and make it long for more. 



