THE POPULAR EDUCATOR 



noticed the marks left on glass by " the flaps," but denied the 

 existence of an adhesive fluid in sufficient quantity to support 

 the weight of a fly. He advocated the sucker theory, giving no 

 less than 12,000 suction tubes on one foot of a common fly. If 

 this statement should stand the test of examinations, we shall 

 then have in one small insect 72,000 suction machines. It may 

 give some readers a clearer view of the minute scrutinies now 

 paade into insect structure when we state that the expanded 

 edge of a fly's foot, called 'the flap," has been found to be only 

 E obr>th of an inch in thickness. 



Mr. Tyrrell and Mr. West have devoted much time to the 

 examination of these " flaps," and the following are the principal 

 results : Two distinct sets of hairs are found on the foot of a 

 fly ; one, called "tenents," rise from the inner side of the flap, 

 and are employed to grip smooth surfaces ; the other series are 

 called " guard hairs," their office being to protect the fine hooked 

 tips of the " tenents " from injury by friction. We must observe 

 here that house-flies are not the only insects furnished with such 

 a double system of hairs most beetles are similarly supplied. 



The fly's apparatus for walking and holding on may be thus 

 summed up : -On a rough surface the insect appears to use its 

 claws only ; on glass, or on a ceiling, three processes are brought 

 into action first, the "almost infinite" number of hairs are 

 pressed down on the smooth surface ; a peculiar movement of 

 the bristles then expels all tlie, air from between or beneath the 

 hair-like cushion ; lastly, a fluid is poured out round the base of 

 the entire hair-pad, and the expelled air is thus prevented from 

 entering. A vacuum is in this manner secured and maintained 

 so long as may be necessary. When the fly wishes to move, the 

 flap, firmly pressed down on the glass, must be first raised, and 

 this is accomplished by the hooked claws which lift up the thin 

 edges of the hair-pad, and thus let in the air and destroy the 

 vacuum. The movement of the claws in this process is very 

 peculiar. Some notion of it may thus be gained : Let a 

 reader suppose that a sucker is fixed to the tip of his little 

 finger, and that this sucker becomes fastened to a table by 

 atmospheric pressure ; let him also imagine the tip of hia 

 thumb to be armed with a number of fine hooks. He will be 

 able to lift the edges of the little finger sucker by these thumb 

 hooks, and thus the air will be admitted under the sucker. Some- 

 what after this fashion does the fly loosen its foot from a surface 

 of glass. 



The insect requires all its force thus to move the feet nimbly. 

 When benumbed by cold or weakened by other causes, the fly 

 remains fixed to one place, unable to lift its feet from the 

 surface. Feeble or diseased flies may sometimes be seen vio- 

 lently struggling to extricate themselves. This was observed 

 by White, who describes the insects as " labouring along and 

 lugging their feet in windows, as if they stuck fast to the glass." 

 Mr. West has endeavoured to estimate the exact amount of the 

 forces which enable a fly to adhere to glass. He found that 

 one-half the insect's weight is supported by the atmospheric 

 pressure on the feet when the vacuum has been produced. One- 

 fourth of the weight is upheld by the grip of the " tenent " 

 hairs, and the remaining fourth part by the fluid emitted from 

 the flaps. As a common house-fly weighs about half a grain, 

 the supporting force exerted by each of the six feet will amount 

 to one-twelfth of a grain only, and this force 'is distributed 

 among three powers the atmospheric pressure, the " tenent " 

 hairs, and the sustaining fluid. Each of these forces would have 

 to support the ^th of a grain only, assuming the weight to be 

 equally distributed throughout. 



W T e have devoted thus much of this paper to the investi- 

 gations of eminent men into the structure of a fiy's foot, with 

 two objects in view to induce some readers to make a more 

 constant use of the microscope in their studies, and to deepen 

 the conviction that there is nothing really little in the works of 

 an infinite mind. 



The antennce of the fly, or feelers, as some call them, must 

 not detain us long, but we cannot pass over some peculiarities 

 of structure in these organs. The third point in the antennae of 

 the blue-bottle fly (Musca vomitoria) is pierced with exceed- 

 ingly fine apertures, the diameter of each being only 50 ^th of 

 an inch. So numerous are these openings that both antennas 

 are estimated to contain 17,000. The mouth of each tube is 

 protected by a fine curtain-like membrane, behind which a 

 minute sac full of fluid can be seen. Some naturalists regard 

 this singular system of apertures and sat 5 as forming the ear 



of the fly. This can, however, only rank at present as a clever 

 supposition, which subsequent discoveries may prove to be true. 



The proboscis or trunk of the fly consists of many suction 

 tubes, admirably fitted for pumping up the fluids on which the 

 insect feeds. This trunk would admit of a much longer 

 description than our space allows ; we must, however, remind 

 the reader that a fly's proboscis really contains tongue, jaws, 

 and lips, all modified and combined in one organ. The tongue 

 is a net-work of fine tubes ; two fine hooks are visible near the 

 tip, one on each side, and the extremity is furnished with a 

 series of most delicate vessels, through which the food passes 

 up to the more fleshy parts of the tongue. An elaborate system 

 of exceedingly minute muscles draws out and retracts the tongue, 

 and aids in rolling up the whole trunk when the insect has 

 finished its meal. As nothing but a fluid can ascend the fine 

 tubes, it might be supposed that no fly could dine off a solid 

 lump of sugar. But the insect is able to dissolve such a sub- 

 stance by a liquid poured from the trunk, and thus the liquefied, 

 sugar is easily drawn up the suction vessels. 



The eyes of a fly are very large when compared with the size 

 of the head. If one of these compound eyes be examined under 

 a glass with a linear magnifying power of 100, the organ will 

 be found to consist of many thousand tubes, each fixed in a six- 

 sided case. Every one of these eyelets appears to be a perfect 

 simple eye, resembling in all essentials that of man. Dr. Hooko 

 gave the number of eyelets in each eye at 7,000, and Dr. Car- 

 penter estimates them at 4,000. Thus, at the lowest compu- 

 tation, a house-fly possesses 8,000 separate organs of vision. 



Few insects seem to lead a happier life than this nimble little 

 creature. But its days are not always free from trouble ; a, 

 disease of a peculiar character attacks the fly, producing a 

 white eruption on the body, suggesting the idea of insect 

 leprosy. The fly is also infested by little parasitic animals, 

 which some enthusiastic naturalists have carefully figured and 

 described. 



Many persons may ask, what special service do flies perform 

 in the system of Nature ? Their particular office appears to be 

 the rapid consumption of those dead and minute animals whoso 

 decaying myriads would, otherwise, soon poison the air. It was 

 a remark of Linnaeus, that three flies would consume a dead 

 horse sooner than a lion could. He, doubtless, included the 

 families of the three flies, then he was certainly right. A single 

 fly will sometimes produce 20,000 larvaa, each of which in a l'u\v 

 days may be the parent of another 20,000, and thus tho 

 descendants of three flies would soon devour an animal much 

 larger than a horse. 



Our readers will see, in the preceding remarks, that even a 

 common house-fly can offer to a student of Nature many marvels 

 of structure, and numerous proofs of an infinite intelligence in 

 the almost invisible organs of the meanest creatures. 



HEADINGS IN FRENCH. II. 



LE SAPEUE DE DIX ANS. 



SECTION V. 



A PARTIE de ce jour, on ne se moqua (a) plus autant du petit 

 Bilboquet, 1 mais il n'en devint (6) pas pour cela plus commu- 

 nicatif ; au contraire, il semblait rouler dans sa tete quelquo 

 fameux projet, et, au lieu do (c) depenser son argent avec ses- 

 camarades, comme ceux-ci s'y attendaient, il le serra soigneusc- 

 ment. 2 



Quelque temps apres, les troupes francaises entrerent a 

 Smolensk, 3 victorieuses et pleines d'ardeur; Bilboquet en etait, 

 et le jour memo de 1'arrivee, il alia se proinener (d) dans la 

 ville, 1 paraissant tres-content de presque tous les visages qu'il 

 rencontrait ;" il les considerait d'un air riant 6 et semblait les 

 examiner comme un amateur qui choisit des marchandises. II 

 faut (e) vous dire cependant, qu'il ne regardait ainsi que les 

 paysans qui portaient (/) de grandes barbes. 7 Elles etait-nt 

 sans doute tres-longues et tres-fournies (g), mais d'un roux si 

 laid, qu' apres un moment d'examen Bilboquet tournait la teto 

 et allait plus loin. Enfin, en allant ainsi, notre tambour arriva 

 au quartier des Juifs. 8 Les Juifs a Smolensk, comme dans 

 toute la Pologne et la Eussie, vendent toutes sortes d'objets 9 

 et ont un quartier particulier. 10 Des que Bilboquet y (h) fut 

 entrc, ce fut pour lui un veritable ravissement : u imaginez-vous 

 les plus belles barbes du monde, noires comme de 1'ebene ; 12 

 car la nation juivo toute dispersee qu'elle est, parmi les autres 



