SOCIETIES OF INSECTS.
IMPERFECT SOCIETIES.
I see already, and I see it with pleasure, that you will not content yourself with being a mere collector of insects. To possess a cabinet well stored, and to know by what name each described individual which it contains should be distinguished, will not satisfy the love that is already grown strong in you for my favourite pursuit; and you now anticipate with a laudable eagerness, the discoveries that you may make respecting the history and economy of this most interesting department of the works of our Creator. I hail with joy this intention to emulate the bright example, and to tread in the hallowed steps of Swammerdam, Leeuwenhoek, Redi, Malpighi, Vallisnieri, Ray, Lister, Reaumur, De Geer, Lyonnet, Bonnet, the Hubers, &c.; and I am confident that a man of your abilities, discernment, and observation will contribute, in no small degree, to the treasures already poured into the general fund by these your illustrious predecessors.
I feel not a little flattered when you inform me that the details contained in my late letters relative to this subject, have stimulated you to this noble resolution.--Assure yourself, I shall think no labour lost, that has been the means of winning over to the science I love, the exertions of a mind like yours.
But if the facts already related, however extraordinary, have had power to produce such an effect upon you, what will be the momentum, when I lay before you more at large, as I next purpose, the most striking particulars of the proceedings of insects in society, and show the almost incredibly wonderful results of the combined instincts and labours of these minute beings? In comparison with these, all that is the fruit of solitary efforts, though some of them sufficiently marvellous, appear trifling and insignificant: as the works of man himself, when they are the produce of the industry and genius of only one, or a few individuals, though they might be regarded with admiration by a being who had seen nothing similar before, yet when contrasted with those to which the union of these qualities in large bodies has given birth, sink into nothing, and seem unworthy of attention. Who would think a hut extraordinary by the side of a stately palace, or a small village when in the vicinity of a populous and magnificent city?
Insects in society may be viewed under several lights, and their associations are for various purposes and of different durations.
There are societies the object of which is mutual defence; while that of others is the propagation of the species. Some form marauding parties, and associate for prey and plunder;--others meet, as it should seem, under certain circumstances, merely for the sake of company;--again, others are brought together by accidental causes, and disperse when these cease to operate;--and finally, others, which may be said to form proper societies, are associated for the nurture of their young, and, by the union of their labours and instincts, for mutual society, help, and comfort, in erecting or repairing their common habitation, in collecting provisions, and in defending their fortress when attacked.
With respect to the duration of the societies of insects, some last only during their first or larva state; and are occasionally even restricted to its earliest period;--some again only associate in their perfect or imago state; while with others, the proper societies for instance, the association is for life. But if I divide societies of insects into perfect and imperfect, it will, I think, enable me to give you a clearer and better view of the subject. By perfect societies I mean those that are associated in all their states, live in a common habitation, and unite their labours to promote a common object;--and by imperfect societies, those that are either associated during part of their existence only, or else do not dwell in a common habitation, nor unite their labours to promote a common object. In the present letter I shall confine myself to giving you some account of imperfect societies.
Imperfect societies may be considered as of five descriptions:--associations for the sake of company only--associations of males during the season for pairing--associations formed for the purpose of travelling or emigrating together--associations for feeding together--and associations that undertake some common work.
The first of these associations consists chiefly of insects in their perfect state. The little beetles called whirlwigs (Gyrinus),--which may be seen clustering in groups under warm banks in every river and every pool, and wheeling round and round with great velocity; at your approach dispersing and diving under water, but as soon as you retire resuming their accustomed movements,--seem to be under the influence of the social principle, and to form their assemblies for no other purpose than to enjoy together, in the sunbeam, the mazy dance. Impelled by the same feeling, in the very depth of winter, even when the earth is covered with snow, the tribes of Tipulariæ (usually, but improperly, called gnats) assemble in sheltered situations at midday, when the sun shines, and form themselves into choirs, that alternately rise and fall with rapid evolutions[1]. To see these little aëry beings apparently so full of joy and life, and feeling the entire force of the social principle in that dreary season, when the whole animal creation appears to suffer, and the rest of the insect tribes are torpid, always conveys to my mind the most agreeable sensations. These little creatures may always be seen at all seasons amusing themselves with these choral dances; which Mr. Wordsworth, in one of his poems[2], has alluded to in the following beautiful lines:
"Nor wanting here to entertain the thought, Creatures that in communities exist, Less, as might seem, for general guardianship Or through dependance upon mutual aid, Than by participation of delight, And a strict love of fellowship combined. What other spirit can it be that prompts The gilded summer flies to mix and weave Their sports together in the solar beam, Or in the gloom and twilight hum their joy?"
Another association is that of males during the season of pairing. Of this nature seems to be that of the cockchafer and fernchafer (Melolontha vulgaris and Amphimalla solstitialis), which, at certain periods of the year and hours of the day, hover over the summits of the trees and hedges like swarms of bees, affording, when they alight on the ground, a grateful food to cats, pigs, and poultry. The males of another root-devouring beetle (Hoplia argentea) assemble by myriads before noon in the meadows, when in these infinite hosts you will not find even one female[3]. After noon the congregation is dissolved, and not a single individual is to be seen in the air[4]: while those of M. vulgaris and A. solstitialis are on the wing only in the evening.
At the same time of the day some of the short-lived Ephemeræ assemble in numerous troops, and keep rising and falling alternately in the air, so as to exhibit a very amusing scene. Many of these also are males. They continue this dance from about an hour before sun-set, till the dew becomes too heavy or too cold for them. In the beginning of September, for two successive years, I was so fortunate as to witness a spectacle of this kind, which afforded me a more sublime gratification than any work or exhibition of art has power to communicate.--The first was in 1811:--taking an evening walk near my house, when the sun declining fast towards the horizon shone forth without a cloud, the whole atmosphere over and near the stream swarmed with infinite myriads of Ephemeræ and little gnats of the genus Chironomus, which in the sun-beam appeared as numerous and more lucid than the drops of rain, as if the heavens were showering down brilliant gems.--Afterwards, in the following year, one Sunday, a little before sun-set, I was enjoying a stroll with a friend at a greater distance from the river, when in a field by the road-side the same pleasing scene was renewed, but in a style of still greater magnificence; for, from some cause in the atmosphere, the insects at a distance looked much larger than they really were. The choral dances consisted principally of Ephemeræ, but there were also some of Chironomi; the former, however, being most conspicuous, attracted our chief attention--alternately rising and falling, in the full beam they appeared so transparent and glorious, that they scarcely resembled any thing material--they reminded us of angels and glorified spirits drinking life and joy in the effulgence of the Divine favour[5]. The bard of Twickenham, from the terms in which his beautiful description of his sylphs is conceived in The Rape of the Lock, seems to have witnessed the pleasing scene here described:
"Some to the sun their insect wings unfold, Waft on the breeze, or sink in clouds of gold; Transparent forms, too fine for mortal sight, Their fluid bodies half dissolv'd in light; Loose to the wind their airy garments flew, Thin glittering textures of the filmy dew, Dipt in the richest tincture of the skies, Where light disports in ever mingling dyes, While every beam new transient colours flings, Colours that change whene'er they wave their wings."
I wish you may have the good fortune next year to be a spectator of this all but celestial dance. In the mean time, in May and June, their season of love, you may often receive much gratification from observing the motions of a countless host of little black flies of the genus Hilara, (H. maura,) which at this period of the year assemble to wheel in aëry circles over stagnant waters, with a rush resembling that of a hasty shower driven by the wind.
The next description of insect associations is of those that congregate for the purpose of travelling or emigrating together. De Geer has given an account of the larvæ of certain gnats (Tipulariæ) which assemble in considerable numbers for this purpose, so as to form a band of a finger's breadth, and of from one to two yards in length. And, what is remarkable, while upon their march, which is very slow, they adhere to each other by a kind of glutinous secretion; but when disturbed they separate without difficulty[6]. Kuhn mentions another of the same tribe (from the antennæ in his figure, which is very indifferent, it should seem a species of agaric-gnat (Mycetophila)), the larvæ of which live in society and emigrate in files, like the caterpillar of the procession-moth. First goes one, next follow two, then three, &c., so as to exhibit a serpentine appearance, probably from their simultaneous undulating motion and the continuity of the files; whence the common people in Germany call them (or rather the file when on march) heerwurm, and view them with great dread, regarding them as ominous of war. These larvæ are apodes, white, subtransparent, with black heads[7].--But of insect emigrants none are more celebrated than the locusts, which, when arrived at their perfect state, assemble as before related, in such numbers, as in their flight to intercept the sunbeams, and to darken whole countries; passing from one region to another, and laying waste kingdom after kingdom:--but upon these I have already said much, and shall have occasion again to enlarge.--The same tendency to shift their quarters has been observed in our little indigenous devourers, the Aphides. Mr. White tells us, that about three o'clock in the afternoon of the first of August 1785, the people of the village of Selborne were surprised by a shower of Aphides or smother-flies, which fell in those parts. Those that walked in the street at that juncture found themselves covered with these insects, which settled also upon the hedges and in the gardens, blackening all the vegetables where they alighted. His annuals were discoloured by them, and the stalks of a bed of onions quite coated over for six days after. These armies, he observes, were then, no doubt, in a state of emigration, and shifting their quarters; and might have come from the great hop-plantations of Kent or Sussex, the wind being all that day in the east. They were observed at the same time in great clouds about Farnham, and all along the vale from Farnham to Alton[8]. A similar emigration of these flies I once witnessed, to my great annoyance, when travelling later in the year, in the Isle of Ely. The air was so full of them, that they were incessantly flying into my eyes, nostrils, &c.; and my clothes were covered by them. And in 1814, in the autumn, the Aphides were so abundant for a few days in the vicinity of Ipswich, as to be noticed with surprise by the most incurious observers.
