[[p. 294]] Insect Variety: its Propagation and Distribution. Treating of the Odours, Dances, Colours, and Music in all Grasshoppers, Cicadae, and Moths; Beetles, Leaf-insects, Bees, and Butterflies; Bugs, Flies, and Ephemerae; and exhibiting the bearing of the Science of Entomology on Geology. By A. H. Swinton, Member of the Entomological Society of London. (Cassell, Petter, Galpin & Co.)

     Mr. Swinton begins his work with a pleasant Introduction, giving an account of his early studies and entomological rambles, with bright sketches of Hampshire cliffs and Surrey downs, of the chalk hills of Kent and the wild crags of Braemar. Having his attention drawn to the sounds produced by insects, he was led to make the various subjects enumerated in the title his special study. He went to Italy chiefly to hear the cicadas sing, though not also without a keen appreciation of its treasures of antiquity and art, as many passages in his book show. As an entomologist, however, he was somewhat disappointed with Italy, which seems to be, for the most part, as much cultivated as our own country. He tells us that its poetic fields and classic ground have few charms for the fly-catcher. "Old in civilisation, the virgin coronet of deer-forest and brake has long fallen from her brow." Italy is emphatically an exotic garden, a land of vine and olive, or a waste of waving grain; and the weary collector often sits down disappointed. After much searching he finds the object of his journey, and thus he describes his success:--

"Sitting down mechanically on the partially dried grass, while the trees around drew in their shadow, I listlessly watched the clouds form in the clear sky around the frosty pinnacle of the Grand Paradiso; and then mustering insensibly, stretch out their gauzy veil over the couchant mass of Monte Bianco and the distant Cenis, till one by one the grand old cordon of barrier giants, together with the ruddy lower spurs of the Albigensian valleys, were replaced by a curtain of opal gray sky, from which stood out sharply the long willow rows fringing the opposite bank, the neighbouring farm, and herded cow . . . Suddenly I fancied I heard a frog quacking in a bush at hand. And then came the sounds, Pip! Pip! Turning over the brittle boughs, which have an unpleasant fashion of breaking off short, I turned up a drowsy Cicada on a damp spray, who was attuning his lyre to the stray glints that crept in among the dense soft foliage. But can this be the Cicada of one's school-days? I exclaimed. It is nothing like a 'Grasshopper,' as elegant writers such as Pope and Dryden maintain; nor does it seem as if it would hop, as Wordsworth and Goethe would make out. No, it is not a treehopper. Cowley said it danced. No; I don't think it dances. And it is not a Cricket, as [[p. 295]] another wiseacre, a German, has it! Nor a Leaf-cricket, with a curly tail, as La Fontaine illustrates it! It used to turn its eyes and wink at St. Franciscus, but alas! its optics have become immoveable."

And thus our author runs on for fourteen pages, with long quotations from Virgil, Meleager, and a host of other poets and writers, classical and modern, so that the reader finds he has to do with no mere dry naturalist, but one who can illustrate his subject by references from the whole field of literature.

     Passing on to the body of the work we find chapters on the nervous system, the passions, and the secretions of insects, with deductions as to their senses of touch and smell; on their dances and display during the breeding season, with a discussion on the corresponding sense of sight; on instrumental music or the various sounds produced by insects, and on the organ and sense of hearing; with a concluding chapter on migration, variation, and natural selection. These subjects are all treated with a large amount of knowledge obtained both by reading and observation; and they are well illustrated by a number of plates and figures, which, if often roughly drawn, are sufficiently characteristic. At the end of each chapter the most important facts and observations are collected into tables, which are of considerable value as presenting a summary of what has been done in this interesting department of entomology. To the working entomologist, therefore, the book will be a useful one; while the general reader with a taste for natural history will find a number of most interesting details on the structure, the senses, and the habits of insects. Such, especially, is the account of the sounds produced by different species of butterflies and moths, which are far more numerous and varied than is generally supposed; and the full description of what is known of the position and structure of the organ of hearing in the different families of insects. It was once supposed that this sense resided in the antennae, but this is now known to be incorrect in many cases. In the cicadae the ear is believed to be situated at the base of the abdomen; in the acrididae, or grasshoppers, on the side of the body under the elytra. Our author says:--

"If any one will observe the grasshoppers in the meadows, it will be noticed how the male, on the conclusion of his music, lowers one or both femora horizontally, retaining the elytra somewhat raised, thus exposing these membranes (the external ears) until he receives a response; or how, when he seeks to allure the female, he places himself so that the stridor shall impinge directly on one or other of her cavities, which she voluntarily exposes by lowering a femur. The cavities in the latter sex are usually of greater dimensions than in the males, and the drumskin more attenuated."

In the crickets, however, the ears are situated--strange to say--on the forelegs.

     A very full account is given of the colour-varieties of butterflies and moths, and an attempt is made (though not very successfully) to connect these with peculiarities of soil or climate. A very curious fact has, however, been discovered as to the effect of large manufacturing towns in producing variations of colour in moths; and this is believed to be due to the various gases and vapours in the atmosphere, especially where chemical works abound; the delicate tissues of these insects during the larva and pupa stage being especially liable to such influences, while even the perfect insects are susceptible to change of colour from similar causes.

     Great attention has also been given to the motions, attitudes, dances, and courtship of insects, which are all described in great detail, and often from personal observation. There is, however, a tendency to give meaning to every motion and attitude, however insignificant, and it is necessary to be constantly on one's guard against accepting these hypothetical interpretations as realities. They furnish the author with great scope for the development of his peculiar notions, and for the free display of his strangely inconsequent, poetical, and often unintelligible style, bristling with obscure technical phraseology, which forms one of the chief drawbacks to an otherwise invaluable work. A few illustrations of this tendency must be given.

     In discussing the origin of the stridulating organs of insects, he remarks that

"Reciprocating stimulatory friction of articulate parts to express emotion postulates adaptive acquisition, consequent on assumed integumental tendency under attrition to determine a smooth, undulatory surface, and propagation by hereditary transmission."

This is merely obscure, but at other times he is perfectly enigmatical, as when, after describing the music of the male grasshoppers, he adds:--

"Similar is the stimulus that incites singing birds at the time of amour to pour on the woodland enchanting strains, or inflorescence, horticulturally deprived of sexual character, to lavish sweeter colour and perfume."

How the colour and scent of our double roses and pinks can be due to the same stimulus as that which causes birds to sing in the pairing season is a problem worthy of the Sphinx itself.

     As examples of the poetry of science, we may quote the following:--

"Herr Westring has mentioned two other micro-beetles of this group that utter a sound--namely, Berosus luridus, a coleopteron about the size of a grain of sand or pin's head, and the, in this country, rather scarce Sperchus emarginatus, which is scarcely its superior, thus ushering us to the very fount of those passions that fired a Troy and shook the pinnacles of heaven."

Describing the notes of some small autumnal grasshoppers, he says:--

"In the existing rage for cheap music, when flashing lights, impassioned notes, and sweet warblings greet the man of business homeward wending, and drive far into the sorrows of the night, it is scarcely to be wondered refrains so full of small peaceful harmonies as those complaining notes, that each autumn echo beneath the blithe ring of the mowers, should continue a study for poets and musician. And it is thus we not only hear of them blending in the luxuriant tide of song on Transatlantic pianos, but, what is more generally feasible, find them adapted to rhythmic notations by admiring frequenters of the green banks of the Rhine and Alpine glaciers, where they possibly lend much to the charms of the scenery."

Then, after describing the song of these "sweet grasshopper minstrels," he tells of one who,

"with true grasshopper spirit, will continue snatches of recitative, even when the throes of death press upon him, and the golden meads of Proserpine are all his perspective."

     One more example of our author's peculiar style may be quoted. The Painted Lady Butterfly is found very widely scattered over the world, and it often migrates in great swarms, as occurred last year. These phenomena are thus described and commented on:--

"Pyrameis cardui and its varieties sunning on the thistle-bank is a cosmopolitan feature in terrestrial scenery we cannot fly from; it meets us, like a friend far from our native land, on every gravelly waste, where the gardens of coral islets, deep in the dark Pacific, are overhung by the bread-fruit, or where the dusty sands of Africa and lone savannahs of America are imprinted by the hoof of the antelope and buffalo, where the jungle of Bengal echoes to the roar of the tiger, or where the Ceylon elephant crushes through the cane, on ancient lands where the epiornis roved and the emu wanders. Go where you will, there persistently sits the ubiquitous Painted Lady on its heap of shingle or flower-head, just as the Chinese, in their country of gardens, depict it on the rice-tree's pith, from where the eternal snows scarcely melt beneath the spring-tide to where the equator kindles its glowing heats."

     This highly imaginative passage conveys the very erroneous impression that the butterfly is more or less common all over the world. But, on the contrary, it is quite unknown in all South America and the West India Islands (except as a rare straggler in Cuba); in the whole of the Pacific islands it is not certainly known to exist; in the Malay islands it is only known, I believe, from Java; but it occurs in Australia, widely scattered in India, and over the whole of the North temperate zone.

     Next, as to the causes of this wide distribution, our author makes an unnecessary mystery by connecting it in some unintelligible way with geological changes. He goes on thus:--

"The history of this marvellous distribution cannot remain wholly a sealed scroll to the geologist when we take into consideration that the insect, in its wonderful migrations, manifestly affords the thread with which to retrace and unravel the problem, while they, on the other hand, render equally patent the reason of its present uncertainty of appearance in various localities. Thus, at the present day, the migrations of the Painted Lady take a fixed direction in the Northern hemisphere from the tropic towards the pole."

     To explain these facts, however, no geological cause is required. The larva of the butterflies feeds on a great variety of plants, such as thistles and other composites, malvaceae, and boraginaceae. When climatic and other conditions are favourable it breeds in great multitudes in North Africa and Southern Europe, and the hosts thus produced fly northwards simply because they are bounded by a desert or sea to the south. That it is produced in much greater numbers than most other butterflies is probably due to the vast abundance of the thistles and other plants on which it feeds, while the larvae, being spiny, are protected from the attacks of the smaller [[p. 296]] insectivorous birds. We need, therefore, hardly call upon the geologist to explain either the wide distribution or the occasional migrations of this insect.

     Readers of this notice will see that Mr. Swinton's volume is one of a very exceptional character, combining poetry and imagination with science and philosophy; while it is unfortunately deficient in the clear judgment and logical analysis which the subjects discussed require for their proper elucidation. Yet readers of very different tastes may find the work interesting and instructive. The naturalist will appreciate the close observation of insect life displayed by the writer, and will find the large assemblage of facts which he has industriously brought together of considerable value; while, to the less scientific, the picturesque descriptions of scenery and of insect habits, the wealth of literary quotation and allusion, the eccentric style and the enigmatical philosophy, will have a greater attraction.

Alfred R. Wallace.