THE NATURALIST.

Otago Witness, Issue 2690, 4 October 1905, Page 76

THE NATURALIST.

Insects' Walking 1 Outfit*.

—Wonderful Gifts "With Which Nature Has Endowed Them. — I. Everybody, doubtless, is familiar with ,tb.fc common bluebottle fly, and has ob- , stned, iis fix black ]egs and probabh' concluded that these terminate in six feet.

Now, if a. detached l^g of the blowfly is seen by a person, possessing normal visipn he- would have little difficulty in aruying at iho conclusion ihat he was looking at the leg of a fly, and -if it should be vieived through a reading glasb it would probably be even more easily distinguished as such, writes John J. Ward in the English Illustrated Magazine. But novelet us place under a microscope a small portion of ibis insect's leg, which roughly measures |in un length ; say we magnify the twenty-fifth part jf an inoh of the fcot end, and see what is then revealed. I vender how many of my readers woul'i! recognise- these objects as tiny portions from the foot end of the legs of the fanviiar blowfly — yet such is the fact. It wili be seen that various details have come i>. to ■siew which previously wore quite unknown Ito us. What are these curious structures, and what is their function? are questions that naturally follow.

In the first place, it is obvious that each foot of the blowfly Is provided with a pair of stout claws. . Those ara of service to ihe insect when walking over rough surfaces or penetrating tiny crevices quite invisible 10 human sight. For example, when it climbs a perpendicular wall or walks upside- down upon a ceiling, the apparently -smooth surface has sufficient roughness for these tuny .-laws to get a grip on it. How-ever, it occasionally occurs thdt the blowfly has other situations to meet, where- it cannot use these hoo.ced claws to any advantage. For instance, in its casual roaming it may alight upon the smooth surface of the butcher's scales and dishes, or occasionally it appears to confuse th-o transparent window panes of the shop with the surrounding atmosphere. In the latter case we sco it butting at the glass, with alternate rambles up and down the pane, as if it were in a great state oi perplexity over the Inexplicable discovery that a portion of the atmosphere had suddenly beooiie tough bnd hard to penetrate. The point we need to particularly observe, however, is that the fly walks up the perpendicular smooth glass with perfect ease, although there is here no rough surface on which its elawts can find a hold. This brings' us to the next poimt in the anatomy of the foot of this insect— namely, the two pads seen between the claws. These pads are brought into play on such snooth surfaces as that of glass and similar material", the claws being then thrown back, one to each side, beneath the foot and out of the way; just as v;hen the claws are in use the pads are lifted up between them, also to be out of the way. These pads or flaps act by adhesion, amd for^a long time were thought to hold, like suckers, by forming a vacuum; but when seme flies were put into a vessel from which the air was withdrawn, and the flies still adhered, it was conclusively shown that a mistake had been made, and some other explanation was necessary. Since then, it has been observed that the under side of these foot flaps is studded with tiny hairs, which exude a sticky fluid, amd it has therefore been surmised that this secretion both expels the air from beneath the pads and at the same time gums the pads to the smooth surface. In this way it is explained that whon 'wo find a dead fly still r adhering- to a window pane or frame it secreted this stick? fluid while its strength was failing, and later became too. feeble to remove its foot again. Of course, a hold of this kind would <?tand a considerable piil' and so it bears the weight of the fly when upside clown. When the active fly would lift its foot it loosens t')c pad by rolling it off the surface from opposite sides, jusj as we might readily open aw envelope by pulling up the flap by il-e point before it has properly stuck, although it would bo extremely difficult to open Ly pulling idireotlv from above.

Although various views in explanation of the exact use of these adhesive organs, which are familiar on many other flies besides, the blowfly, and rlso on bees, butterflies, and other insects, have been put forward from time to time, yet that given here is perhaps the most probable and the enc most largely accepted among zoologists. The remaining structures worthy of notice ii> the blowfly's foot are the stout bristles which clothe its joints and also the longer Pttd .more deli:-ate ones, termed touch br-.stles, seen nearest the pads, which arc probably * ssooiatc-d with the sense of touch, and serve to direct the insect to suitable foothold". The coarser bristles may serve a variety of purposes in the economy of the insect, acting as brushes, combs, etc., as may be observed by watching a fly arranging its toilet.

There is another variety of the pad and claw arrangement. This example is that of an ichneumon fly--a parasitic fly who=e business it is to seek out plump and heaß'iy cnterpillars and carefully deposit its os>as in their bodies Its offspring eventually feeding on the substance of their catei pillar host. Now. if the reader will think for on©

[ moment of this insect's occupation, and I then glance at its strong cornb-iike claw 3 and consider tbe plump and soft bodies of tbe caterpillars it has to deal with, jio large effort of the imagination will be required to understand how iha caterpillars are par--ui'lcd into a gentle submission to the egg'-depositmo business when gripped ! with six f Jet lika th.s.

The Eagls Males But Once.— Tho married life of mo='C birds could ho taken for a model e^en by members of the human family. There * is, for instance, the staid, digvJfied. and homely bald-headed eagle— :_ the glorious emblem of the American Republic. He mates but •■noe. and lives with 1 his mate unt:l he or the dies. If left a widower— even a young widower — the' bald-headed eoglo never mates again. He remains alone and disconsolate in the nest;' en the rocky crag or in the branches of ai tali pine tliat formed his domicile while lv« mat-o was alive. No other female eagle can tempt him to forsake his disconsolate lifj. With him. once a widower, always a widower. The golden woodpeckers live in a happy married state, mating but ones. It "the male dies, his rr.are'* grief is lasting, and she lives a. widou-cd I'ird tho rest of her life. So, too. the male woodnec^or never seeks another mate after Ihe death of his own. Ho taps on a tree beside their nest day and night, trying to tecall her: then at length, discouraged and hopeless, he becomes silent and nc^er recovers his gaiety. — Chicago Tribute.

A Cuclcca and Its Egg. — An interesting instance of the- mode in which the cuckoo deposits its egg is recorded by the Rev. W. W. Flemyng. on the testimony of a trustworthy eye-witness, in the July number of the Irish Naturalist. On May 23 a farmer living near Coolfin. Portlaw, Ireland, observed a cuckoo hovering lound a particular spot near a small clump of trorse. On going up io the spot the observer found a meadow pipit's nest containing three eggs. Hiding- behind a fence, he soon saw the cuckoo reappear, when the bird, after a few minutes, laid an egar on the ground', which it carried almost immediately after in its beak and placed in the- nest ~of the meadow pipit. In the nes+, tho cuckoo had one of the meadow pipit's eggs in its beak, and this eg;? was sursequently found on the ground a few yards off, broken in two and its contents spilt. Although the cuckoo's e?g was considerably larger than the eggs if the meadow pipit, from which it also differed somewhat in colour, yet it did not appear conspicuously distinct from the, two latter as ifc lay in Ihe nest. There is, of course, nothing new, in thi? observation. It merely confirms a fact which has long been known.

Nest of the Paradise Fish.— After Ins success in getting the Malay fighting fsh to construct its curious nest of bubbles in captivity, Mi E. E. Waite has turned his attention, with equailv good results, to the» breeding habits of the beautiful paradi?e< fish, or rainbow fish, which is another member of the sarre group, and builds a nest of the ?ame type. According: to a preliminary account communicated by Mr Waits to the Records of the Australian Museum (vol. vi. p. 1). the nest of the paradise fish is smaller and less markedly domeshaped than that of its relative, a difference which may probably be accounted for t.y the fact that the former species is in the habit of constructing its nest beneath some shelter, such as a eourcle of crossing leaves of Valisraeria. The first batch of eggs is laid when there are frequently only a fewbubbles, other bubbles being added as tLe laying goes on. As a consequence of this the eggs are raised completely out, of the water, and then hatched, an apparently unique feature amongst nsh : s. Although' the male takes complete charge of tl*o "nursery" arrangements, the "female is permitted to tako a share In collecting the cgsrs and placing th-em in the nest. On ordinary occasions the mala is chiefly distinguished from the femaie by its larger size and {onset fins, but in the breeding reason the colours of ihe former are in i tonsified. whilo the female becomes very pa.le and loses the beautiful greenish-Mue bars on th-e body Me Waite adds thafi none of the illustrations he has seen do full justioa to this gorgeously colcured fish. —Field.