LETTER XVIII.

_SOCIETIES OF INSECTS._

PERFECT SOCIETIES CONTINUED. (_Wasps and Humble-Bees._)

I shall now call your attention to such parts of the history of two other descriptions of social insects, _wasps_, namely, and _humble-bees_, as have not been related to you in my letters on the affection of insects for their young, and on their habitations. What I have to communicate, though not devoid of interest, is not to be compared with the preceding account of the ants, nor with that which will follow of the hive-bee. This, however, may arise more from the deficiency of observations than the barrenness of the subject.

The first of these animals, _wasps_, (_Vespa_)--with whose proceedings I shall begin,--we are apt to regard in a very unfavourable light. They are the most impertinent of intruders. If a door or window be open at the season of the year in which they appear, they are sure to enter. When they visit us, they stand upon no ceremony, but make free with every thing that they can come at. Sugar, meat, fruit, wine, are equally to their taste; and if we attempt to drive them away, and are not very cautious, they will often make us sensible that they are not to be provoked with impunity. Compared with the bees, they may be considered as a horde of thieves and brigands; and the latter as peaceful, honest, and industrious subjects, whose persons are attacked and property plundered by them. Yet, with all this love of pillage and other bad propensities, they are not altogether disagreeable or unamiable; they are brisk and lively; they do not usually attack unprovoked; and their object in plundering us is not purely selfish, but is principally to provide for the support of the young brood of their colonies.

The societies of wasps, like those of ants and other social _Hymenoptera_, consist of females, males, and workers. The _females_ may be considered as of two sorts: first, the females by way of eminence, much larger than any other individuals of the community, equalling six of the workers (from which in other respects they do not materially differ) in weight, and laying both male and female eggs. Then the small females, not bigger than the workers, and laying only male eggs. This last description of females, which are found also both amongst the humble-bees and hive-bees, were first observed amongst the wasps by M. Perrot, a friend of Huber's[115]. The large females are produced later than the workers, and make their appearance in the following spring; and whoever destroys one of them at that time, destroys an intire colony, of which she would be the founder. They are more worthy of praise than the queen-bee; since upon the latter, from her very first appearance in the perfect state no labour devolves,--all her wants being prevented by a host of workers, some of which are constantly attending upon her, feeding her, and permitting her to suffer no fatigue; while others take every step that is necessary for the safety and subsistence of the colony. Not so our female wasp;--she is at first an insulated being that has had the fortune to survive the rigours of winter. When in the spring she lays the foundation of her future empire, she has not a single worker at her disposal: with her own hands and teeth she often hollows out a cave wherein she may lay the first foundations of her paper metropolis; she must herself build the first houses, and produce from her own womb their first inhabitants; which in their infant state she must feed and educate, before they can assist her in her great design. At length she receives the reward of her perseverance and labour; and from being a solitary unconnected individual, in the autumn is enabled to rival the queen of the hive in the number of her children and subjects; and in the edifices which they inhabit--the number of cells in a vespiary sometimes amounting to more than 16,000, almost all of which contain either an egg, a grub, or a pupa; and each cell serving for three generations in a year; which, after making every allowance for failures and other casualties, will give a population of at least 30,000. Even at this time, when she has so numerous an army of coadjutors, the industry of this creature does not cease, but she continues to set an example of diligence to the rest of the community.--If by any accident, before the other females are hatched, the queen mother perishes, the neuters cease their labours, lose their instincts, and die.

The number of females in a populous vespiary is considerable, amounting to several hundred; they emerge from the pupa about the latter end of August, at the same time with the males, and fly in September and October, when they pair. Of this large number of females, very few survive the winter. Those that are so fortunate remain torpid till the vernal sun recalls them to life and action. They then fly forth, collect provision for their young brood, and are engaged in the other labours necessary for laying the foundation of their empire: but in the summer months they are never seen out of the nest.

The _male_ wasps are much smaller than the female, but they weigh as much as two workers. Their antennæ are longer than those of either, not, like theirs, thicker at the end, but perfectly filiform; and their abdomen is distinguished by an additional segment. Their numbers about equal those of the females, and they are produced at the same time. They are not so wholly given to pleasure and idleness as the drones of the hive. They do not, indeed, assist in building the nest, and in the care of the young brood; but they are the scavengers of the community; for they sweep the passages and streets, and carry off all the filth. They also remove the bodies of the dead, which are sometimes heavy burthens for them; in which case two unite their strength to accomplish the work; or, if a partner be not at hand, the wasp thus employed cuts off the head of the defunct, and so effects its purpose. As they make themselves so useful, they are not, like the male bees, devoted by the workers to an universal massacre when the impregnation of the females, the great end of their creation, is answered; but they share the general lot of the community, and are suffered to survive till the cold cuts off them and the workers together.

The _workers_ are the most numerous, and to us the only troublesome part of the community; upon whom devolves the main business of the nest. In the summer and autumnal months, they go forth by myriads into the neighbouring country to collect provisions; and on their return to the common den, after reserving a sufficiency for the nutriment of the young brood, they divide the spoil with great impartiality;--part being given to the females, part to the males, and part to those workers that have been engaged in extending and fortifying the vespiary. This division is voluntarily made, without the slightest symptom of compulsion. Several wasps assemble round each of the returning workers, and receive their respective portions. It is curious and interesting to observe their motions upon this occasion. As soon as a wasp, that has been filling itself with the juice of fruits, arrives at the nest, it perches upon the top, and disgorging a drop of its saccharine fluid, is attended sometimes by two at once, who share the treasure: this being thus distributed, a second and sometimes a third drop is produced, which falls to the lot of others.

Another principal employment of the workers is the enlarging and repairing of the nest. It is extremely amusing to see them engaged upon this foliaceous covering. They work with great celerity; and though a large number are occupied at the same time, there is not the least confusion. Each individual has its portion of work assigned to it, extending from an inch to an inch and a half, and is furnished with a ball of ligneous fibre, scraped or rather plucked by its powerful jaws from posts, rails, and the like. This is carried in its mouth, and is thus ready for immediate use:--but upon this subject I have enlarged in a former letter[116]. The workers also clean the cells and prepare them to receive another egg, after the imago is disclosed and has left it.

There is good reason for thinking, and the opinion has the sanction of Sir Joseph Banks, that wasps have sentinels placed at the entrances of their nests, which if you can once seize and destroy, the remainder will not attack you. This is confirmed by an observation of Mr. Knight's in the _Philosophical Transactions_[117], that if a nest of wasps be approached without alarming the inhabitants, and all communication be suddenly cut off between those out of the nest and those within it, no provocation will induce the former to defend it and themselves. But if one escapes from within, it comes with a very different temper, and appears commissioned to avenge public wrongs, and prepared to sacrifice its life in the execution of its orders. He discovered this when quite a boy.

It sometimes happens, that when a large number of female wasps have been observed in the spring, and an abundance of workers has in consequence been expected to make their attack upon us in the summer and autumn, but few have appeared. Mr. Knight observed this in 1806, and supposes it to be caused by a failure of males[118]. I have since more than once made the same observation, and Major Moor, as well as myself, noticed in the year 1815. What took place here in the following year may in some degree account for it. Though the summer had been very wet, and one may almost say winterly, there were in the neighbourhood in which I reside abundance of wasps at the usual time; but, except on some few warm days, in which they were very active, benumbed by the cold they were crawling about upon the floors of my house and seemed unable to fly. In this vicinity numbers make their nests in the banks of the river. In the beginning of the month of October there was a very considerable inundation, after which not a single wasp was to be seen. The continued wet that produces an inundation may also destroy those nests that are out of the reach of the waters;--and perhaps this cause may have operated in those years above alluded to, in which the appearance of the workers in the summer and autumn did not correspond with the large numbers of females observed in the spring.

In ordinary seasons, in the month lately mentioned, October, wasps seem to become less savage and sanguinary; for even flies, of which earlier in the summer they are the pitiless destroyers, may be seen to enter their nests with impunity. It is then, probably, that they begin to be first affected by the approach of the cold season, when nature teaches them it is useless longer to attend to their young. They themselves all perish, except a few of the females, upon the first attack of frost.

Reaumur, from whom (see the sixth Memoir of his last volume) most of these observations are taken, put the nests of wasps under glass hives, and succeeded so effectually in reconciling these little restless creatures to them, that they carried on their various works under his eye: and if you feel disposed to follow his example, I have no doubt you will throw light upon many parts of their history, concerning which we are now in darkness.

* * * * *

Having given you some idea, imperfect indeed from the want of materials, of the societies of wasps, I must next draw up for you the best account I can of those of the _humble-bees_[119]. These form a kind of intermediate link between the wasps and the hive-bees, collecting honey indeed and making wax, but constructing their combs and cells without the geometric precision of the latter, and of a more rude and rustic kind of architecture; and distinguished from both, though they approach nearer to the bees, by the extreme hairiness of their bodies.

The population of a humble-bees nest may be divided into four orders of individuals: the large females; the small females; the males; and the workers.

The large _females_, like the female wasps, are the original founders of their republics. They are often so large, that by the side of the small ones or the workers, which in every other respect they exactly resemble, they look like giants opposed to pygmies. They are excluded from the pupa in the autumn; and pair in that season, with males produced from the eggs of the small females. They pass the winter under ground, and, as appears from an observation of M. P. Huber, in a particular apartment, separate from the nest, and rendered warm by a carpeting of moss and grass, but without any supply of food. Early in the spring, (for they make their first appearance as soon as the catkins of the sallows and willows are in flower,) like the female wasps, they lay the foundations of a new colony without the assistance of any neuters, which all perish before the winter. In some instances however, if a conjecture of M. de la Billardière be correct, these creatures have an assistant assigned to them. He says, at this season (the approach of winter) he found in the nest of _Bombus Sylvarum_ some old females and workers, whose wings were fastened together to retain them in the nest by hindering them from flying; these wings in each individual were fastened together at the extremity, by means of some very brown wax applied above and below[120]. This he conceives to be a precaution taken by the other bees to oblige these individuals to remain in the nest and take care of the brood that was next year to renew the population of the colony. I feel, however, great hesitation in admitting this conjecture, founded upon an insulated and perhaps an accidental fact. For, in the first place, the young females that come forth in the autumn, and not the old ones, are the founders of new colonies; and their instinct directs them to fulfill the great laws of their nature without such compulsion; and in the next, the workers are never known to survive the cold of winter.

The employment of a large female, besides the care of the young brood before described, and the collecting of honey and pollen, is principally the construction of the cells in which her eggs are to be laid; which M. P. Huber seems to think, though they often assist in it, the workers are not able to complete by themselves. So rapid is the female in this work, that to make a cell, fill it with pollen, commit one or two eggs to it, and cover them in, requires only the short space of half an hour. Her family at first consists only of workers, which are necessary to assist her in her labours; these appear in May and June: but the males and females are later, and sometimes are not produced before August and September[121]. As in the case of the hive-bee, the food of these several individuals differs; for the grubs that will turn to workers are fed with honey and pollen mixed, while those that are destined to be males and females are supplied with pure honey.

The instinct of these larger females does not develop itself all at once: for it is a remarkable fact, that when they are first hatched in the autumn, not being in a condition to become mothers, they are no object of jealousy to the small queens, (as we shall soon see they are when engaged in oviposition,) and are employed in the ordinary labours of the parent nest--that is, they collect honey and pollen, and make wax; but they do not construct cells. The building instinct seems as it were in suspense, and does not manifest itself till the spring; when the maternal sentiment impels them at the same time to lay eggs and to construct the cells in which they are to be deposited.

I have told you above, that amongst the wasps a _small_ kind of _female_ has been discovered: this is the case also amongst the humble-bees, in whose societies they are more readily detected: not indeed by any observable difference between them and the workers, but chiefly by the diversity of their instincts:--from the other females they are distinguished solely by their diminutive size. Like those of the wasps and hive-bees, these minor queens produce only male eggs, which come out in time to fertilize the young females that found the vernal colonies. M. P. Huber suspects that, as in the case of the female bee, it is a different kind of food that develops their ovaries, and so distinguishes them from the workers. They are generally attended by a small number of males, who form their court.

M. Huber, watching at midnight the proceedings of a nest which he kept under a glass, observed the inhabitants to be in a state of great agitation: many of these bees were engaged in making a cell; the queen-mother of the colony, as she may be called, who is always extremely jealous of her pygmy rivals, came and drove them away from the cell;--she in her turn was driven away by the others, which pursued her, beating their wings with the utmost fury, to the bottom of the nest. The cell was then constructed, and two of them at the same time oviposited in it. The queen returned to the charge, exhibiting similar signs of anger; and, chasing them away again, put her head into the cell, when seizing the eggs that had been laid, she was observed to eat them with great avidity. The same scene was again renewed, with the same issue. After this, one of the small females returned and covered the empty cells with wax. When the mother-queen was removed, several of the small females contended for the cell with indescribable rage, all endeavouring to lay their eggs in it at the same time. These small females perish in the autumn.

The _males_ are usually smaller than the large females, and larger than the small ones and workers. They may be known by their longer, more filiform, and slenderer antennæ; by the different shape and by the beard of their mandibles. Their posterior tibiæ also want the _corbicula_ and _pecten_ that distinguish the individuals of the other sex, and their posterior plantæ have no auricle. We learn from Reaumur that the male humble-bees are not an idle race, but work in concert with the rest to repair any damage or derangement that may befall the common habitation.

The _workers_, which are the first fruits of the queen-mother's vernal parturition, assist her, as soon as they are excluded from the pupa, in her various labours. To them also is committed the construction of the waxen vault that covers and defends the nest. When any individual larva has spun its cocoon and assumed the pupa, the workers remove all the wax from it; and as soon as it has attained to its perfect state, which takes place in about five days, the cocoons are used to hold honey or pollen. When the bees discharge the honey into them upon their return from their excursions, they open their mouths and contract their bodies, which occasions the honey to fall into the reservoir. Sixty of these honey-pots are occasionally found in a single nest, and more than forty are sometimes filled in a day. In collecting honey, humble-bees, if they cannot get at that contained in any flower by its natural opening, will often make an aperture at the base of the corolla, or even in the calyx, that they may insert their proboscis in the very place where nature has stored up her nectar[122]. M. Huber relates a singular anecdote of some hive-bees paying a visit to a nest of humble-bees placed under a box not far from their hive, in order to steal or beg their honey; which places in a strong light the good temper of the latter. This happened in a time of scarcity. The hive-bees, after pillaging, had taken almost entire possession of the nest. Some humble-bees which remained in spite of this disaster, went out to collect provisions; and bringing home the surplus after they had supplied their own immediate wants, the hive-bees followed them, and did not quit them till they had obtained the fruit of their labours. They licked them, presented to them their proboscis, surrounded them, and thus at last persuaded them to part with the contents of their honey-bags. The humble-bees after this flew away to collect a fresh supply. The hive-bees did them no harm, and never once showed their stings;--so that it seems to have been persuasion rather than force that produced this singular instance of self-denial. This remarkable manœuvre was practised for more than three weeks; when the wasps being attracted by the same cause, the humble-bees entirely forsook the nest[123].

The workers are the most numerous part of the community, but are nothing when compared with the numbers to be found in a vespiary or a beehive:--two or three hundred is a large population for a humble-bees nest; in some species it not being more than fifty or sixty.--They may more easily be studied than either wasps or hive-bees, as they seem not to be disturbed or interrupted in their works by the eye of an observer[124].

I am, &c.

FOOTNOTES:

[115] Huber, _Nouv. Observ._ ii. 443.

[116] VOL. I. p. 501.

[117] For 1807, 242--.

[118] Ibid. 243.

[119] _Bombus. Apis_ * *. e. 2. K.

[120] _Mémoires du Muséum_, &c. i. 55.

[121] P. Huber, in _Linn. Trans._ vi. 264.--This author says however in another place (_ibid._ 285), that the male eggs are laid in the spring, at the same time with those that are to produce workers. Perhaps by the former he means the male offspring of the small females, and by the latter those of the large?

[122] Hub. _Nouv. Observ._ ii. 375.

[123] Ibid. 373--.

[124] This account of the proceedings of humble-bees is chiefly taken from Reaumur, vi. _Mém._ l.; and M. P. Huber in _Linn. Trans._ vi. 214--.