Part 2

The whole problem of the relationships between host and cuckoo is most interesting. In some cases the cuckoos are so like their hosts that it is difficult to tell one from the other, in others they are so unlike that it is difficult to trace any resemblance between them. There are a great number of different kinds of cuckoos, and most of them select a special host to associate {15} with, and are never found except with that species. There are, however, cases of cuckoos which visit the nests of more than one host, and cases of hosts which are visited by several kinds of cuckoos. In the short-tongued bees, with the exception of _Halictus_ and _Sphecodes_, the cuckoos are quite unlike their hosts both in form and colour. In the _Andrenas_ (the lawn bee being one of them) the hosts are clothed with reddish, or brown and black, hairs, and are of a more or less stout build (pl. B, 15, 16). The cuckoos are elegant in shape, almost devoid of hairs, and most of them are striped with yellow or brown across the body so that they present a wasp-like appearance (pl. B, 18). Species more unlike one another than host and cuckoo one could hardly imagine; still this stranger seems to get access to the nest of its host without opposition. In a colony of _Andrena_ one may see the cuckoos (which rejoice in the name of _Nomada_ or wanderers) flying about among the females of the industrious bee, and no alarm or concern appears to be felt by the latter. As we go up in the scale of bees, i.e. towards the more specialized, and arrive at those with longer tongues, the {16} cuckoos are found as a rule to resemble their hosts more closely, both in colour and structure, and when we reach the social genus _Bombus_ (i.e. the humble bees) we find the cuckoos so like their hosts (pl. D, 30, 31) that even entomologists of experience mistake one for the other. _Apis_ (the hive bee) has no cuckoo. It seems to be theoretically probable that both cuckoo and host once originated from common parents; this is suggested by the similarity of structure of certain parts of both host and cuckoo, even in cases where they are otherwise most dissimilar. _Andrena_ and _Nomada_, for instance, which are very unlike, as stated above, agree in both having very feeble stings and in possessing three conspicuous spines on the upper and posterior edge of the orbit of the larva. Also, although _Andrena_ the host has a short tongue, and _Nomada_, its cuckoo, a long one, the appendages (_labial palpi_) of the latter's tongue are framed on the same plan as those of the tongue of _Andrena_, and are quite unlike those of the other long-tongued bees. On the other hand, the cuckoos of the social species resemble them so closely in structure as well as {17} appearance that it is more necessary to search for points of difference than of similarity. There is only one case known of a cuckoo wasp, and that resembles its host even more closely than do the cuckoos of the humble bees. All these points certainly suggest the probability that the social bees and wasps and their cuckoos adopted different habits at a much more recent date than the solitary species, and therefore have not had so much time to become differentiated in structure. The only short-tongued bees which have cuckoos of similar structure are the species of _Halictus_ (pl. B, 12); their cuckoos, _Sphecodes_ (pl. B, 11), are closely allied to them, but then _Halictus_ and _Sphecodes_ are most peculiar genera; although short-tongued, their females spend the winter in the earth, as do the social bees and wasps (see p. 13), and they colonize largely, which may prove to be a step towards socialism.

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{18}

THE FOSSORS OR DIGGERS

In many respects the insects of this section adopt the same methods as the solitary bees so far as the construction of their nests is concerned, but the food brought home for their offspring is animal instead of vegetable. In order to supply their larvae with "fresh meat" these little creatures, when they have captured a suitable prey, sting it in such a way that it becomes paralyzed, but does not die; after provisioning a cell with the necessary number of these paralytics, the mother lays her egg on one of them or amongst them, and closes up the cell. In consequence of this wonderful maternal instinct, foresight, or whatever the faculty may be, the larva when hatched finds fresh food ready for consumption. The various species provision their nests with different kinds of foods, and some appear to be most fastidious in their selection, and are said never to err in choosing {19} species of some particular family, thereby displaying a discernment worthy of any advanced entomologist. Some provision their cells with beetles, some with grasshoppers, others with spiders, caterpillars, plant lice, etc.

The strength possessed by the female fossor must be proportionately enormous, as she can bring back to her burrow, after paralyzing them, insects many times her own size. It is a most interesting sight to see the excitement and flurry of the captor as it tries to drag along some huge prey to its nest. I remember seeing one dragging along a good-sized caterpillar, of a noctuid moth, over rather rough ground: the poor creature had a difficult job; it had to go backwards itself, and pull the body of the caterpillar, after it--its behaviour was very much like that of an ant which has a large burden; at times it would loose its hold of it and try it from some other quarter; however, by degrees, by pulling and tugging, the prey was safely brought home, but the force expended must have been very great. Many species, however, hunt insects of much smaller size than themselves, and it is those which take a fancy to grasshoppers and {20} caterpillars which seem to be the most doughty in deeds of force. One, a very rare kind in this country, sets its affection especially on the honey bee as a prey; the two insects are about equal in size, but the hive bee must be a dangerous foe to attack, and one would have thought as likely to sting its captor as its captor would be to sting it; also one would imagine that a hive bee, unless thoroughly paralyzed, would be a dangerous subject for a juvenile larva to commence making a meal upon! but whether the venture ever turns out unsatisfactorily there are no data to show, so far as I am aware. The larvae must vary very much in their tastes; one can imagine that a nice juicy caterpillar, or even a good fat grasshopper, may be appetizing and easily assimilated, but one can equally fancy that the larvae, who wake up to find their food consisting of small hard beetles, may feel more or less resentment against their parents' ideas of dainties for the young! Still they seem to thrive on it, and come out eventually as exact likenesses of their parents. A large number of the fossors inhabit dry sandy wastes, such as the dunes along the sea coast at Deal, Lowestoft, {21} etc.; many of these, when they leave their burrows, throw up some sand over the hole so as completely to cover it; how these insects find the spot again after a lengthy chase after spiders or other prey is a marvel; and yet those who have observed carefully say that they come home from long distances with unerring precision. No sense of which we have any knowledge, however accentuated, seems to explain this. To be able to arrive back at a home in an extensive arid sandy plain, where no outward sign indicates its whereabouts, must surely require perception of a different nature from any of those with which we are endowed. Some fossors are subject to the depredations of cuckoos, just as the solitary bees are, but their cuckoos are rarely of aculeate origin. The only ones which I have had any opportunity of studying are the species which nest in bramble stems. The cuckoos which associate with them are some of the smaller jewel flies and _Ichneumons_: the habits of both these differ from those of the aculeate cuckoos, the jewel flies devouring the larva of the aculeate and the _Ichneumon_ laying its eggs in it. The fossors {22} [Illustration: FIG. 2.] vary exceedingly in size, shape and colour. Our largest species are about an inch long and our smallest about the eighth of an inch, nearly all having the body where it joins the thorax constricted into a very narrow waist; this is sometimes of considerable length. In one genus known to entomologists by the name _Ammophila_ (fig. 2) or "lover of the sand", the waist is practically the longest part of the body, so that looking at one sideways as it flies along, one could almost be deceived into thinking that there were two insects, one following the other (cf. pl. A, fig. 7). In colour, there seem to be three dominant schemes: Black (cf. pl. B, fig. 17); black with a red band across the body (cf. pl. A, fig. 7); and black banded with yellow, like a wasp (cf. pl. A, figs. 6 and 8, etc.) In some the yellow bands may not be complete, and appear only as spots on each side of the body segments, or the red band may be almost obliterated, or the black species may {23} [Illustration: FIG. 3.] [Illustration: FIG. 4.] be more or less variegated with yellow spots on the head and thorax, but as a general rule all our species fall into one or other of these colour schemes. The females of some of our sand frequenting species have beautiful combs on their front feet, each joint of the tarsi having one or more long spines on its external side (figs. 3 and 4). These are of importance to them in their burrowing, as they enable them to move with one kick of their front leg a considerable amount of the dry sand in which they make their nests. Although sandy commons, etc., are the resort of many fossors, others may be found burrowing in wood or in hard pathways or banks; in fact, like most other insects, some of their members may be found almost anywhere.

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{24}

THE SOLITARY WASPS

The ordinary wasps are acquaintances of every one, but the solitary or keyhole wasps are not so well known, although they are far from uncommon. They are little narrow black insects striped across the body with yellow, belonging to the genus _Odynerus_ (pl. A, 9), and might hardly be recognized as belonging to the same family as the true or social wasps. Still they have considerable powers of stinging, and fold their wings lengthwise when at rest like their larger relatives. I dare say some people may have noticed that a wasp's wing sometimes assumes a narrow straight form, quite unlike what it is when expanded. This is due to the wasp being able to fold its wing lengthwise like a fan. The wasp tribe are, so far as I know, the only stinging Hymenoptera which have this power.

They make their nests of mud, etc., in crevices of walls, in banks, in plant stems, and often {25} in most inconvenient places, such as keyholes, etc. Some of the solitary wasps have a very curious habit of making a tubular entrance to their hole. These may sometimes be seen projecting from sandy banks. The tube is composed of a series of little pellets of mud, which the wasp by degrees, with the help of its mouth secretions, sticks together till a sort of openwork curved tube of sometimes an inch long is formed (fig. 5). This curve is directed downwards, so that the wasp has to creep up it before reaching the actual orifice of the nest. It looks as if the first shower of rain would wash the whole structure away, and I have very little doubt that it often does so. The object of these tubes is difficult to appreciate. There is a bee on the continent which makes straight chimneys above its holes, so as to raise the entrance above the surrounding herbage; possibly these solitary wasps once required {26} their tubes also for some such purpose, and have continued on truly conservative lines to build them long after all usefulness has passed away from the habit; anyhow they are very interesting and beautiful structures. I have found the tubes of one of our rarer species projecting perpendicularly out of the level sand, but even then the tubes were curved over at the end, so that the wasp had to go up and down again before entering its actual hole. The Rev. F. D. Morice in 1906 found the tubes of the same species in numbers projecting from the walls of an old stuccoed cottage situated close to the locality where I found mine, so it is evident that more than one situation suits its requirements. The solitary wasps provision their cells with caterpillars, stinging them in the same way as the fossors do. One very peculiar genus, of one species only in this country, has its body much narrowed at the waist by reason of the constricted form of the basal segment; it makes a little round nest of clay which it suspends from a twig of heather or other plant. This species is rarely met with except on the heathery commons of Surrey, Hants, Dorset, etc. The {27} solitary wasps are subject to the attacks of cuckoos belonging to the jewel fly or _Chrysis_ tribe; these behave differently from those belonging to the aculeate groups, as their larvae do not eat the food laid up for the wasp, but wait till the wasp larva has finished feeding up, and then devour it. Unlike as these cuckoos are to their hosts in their brilliant metallic coloration, etc., they have structural characters curiously like theirs, so that even here a common parentage in bygone generations may be reasonably suspected. At present, however, they are placed, except by a few systematists, in quite distinct families of the Hymenoptera.

In general form these solitary wasps resemble the fossors more than the bees; they have mostly short tongues (I think all our British ones have), and their hairs are simple or more or less spirally twisted.

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{28}

THE SOCIAL GROUPS

The social bees are certainly the most highly specialized of the _Anthophila_, and the social wasps of the _Diploptera_ or insects with folded wings. The ants occupy a less definite position: they would seem to be the outcome of specialization among the fossors, only they feed their young with vegetable juices and not with animal as the latter do. They are always kept as a separate tribe under the name _Heterogyna_, but for our purposes the better known word "ant" will suffice.

The hive bee and the social wasps are the only British Hymenoptera which adopt the hexagonal cell-formation in their nests, the bee fashioning its cells in wax, the wasps and hornet in masticated wood or paper. The formation of ants' nests is far less regular, being composed of irregular passages, called galleries, and open spaces, no doubt built on a plan, but probably {29} in respect of plan no two nests are exactly alike. The humble bees again differ from either in their nesting habits: the female in the spring seeks out a mouse's nest or other suitable foundation of moss, etc., in or on the surface of the ground, according to the species. This she lines with wax, deposits a heap of pollen, and lays her eggs in it. She also makes waxen cells for honey, but these are not hexagonal and symmetrical as are those of the hive bee, but are more like little pots, and are known as "honey pots".

It must be borne in mind that the economic arrangements of the wasps and humble bees only last for a single season, whereas those of the ant and hive bee exist for many years. In consequence of this the swarming habits belong exclusively to the ants and hive bee. That of the hive bee is well known to all, and most people must have observed the swarms of male and female ants which fill the air on some sultry summer or autumn evening. Thousands of these must perish, but a certain number of the females accept the responsibility of starting a fresh nest, and so the ant population is kept up. {30} It will be seen from these remarks that the three social groups are very distinct in their methods of nest making, and have really very little in common except the social habit. The humble bees have their cuckoos; one species of wasp has a cuckoo, and there is a possible case of a cuckoo amongst the continental ants, but this has not yet been observed in this country. The ants harbour so many species of insects in their nests besides their own family that it is difficult to form an idea as to whether the case in question is at all analogous to that of host and cuckoo in the other aculeates or not.

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{31}

THE ANTS

These little creatures are probably the most intelligent of all the insects--and yet at times they seem to wander about almost aimlessly. A worker may be found with an insect or something which it is eagerly dragging along and drops probably from fear. It appears anxious to regain its hold of it, but goes about in all sorts of wrong directions before it again finds it, it may be to make sure its enemy is clear away before it resumes operations, but the effect to the ordinary onlooker is one of sheer incapacity--at the same time the wonderful habits of the tribe, the way in which they keep plant lice for their larvae, their methods of carrying each other, their nest-building, and the slave-making instincts of some of the species, show an intelligence surpassed by no other family of insects. Their nests are formed in very various ways: the same species even will sometimes nest under a stone and sometimes make ant hills; some {32} of the large species make their nests of huge heaps of fir needles, and number 400 to 500 thousand in one nest--others live in quite small communities, nesting in bramble stems, old rotten wood, moss, etc. One little species, rare with us, lives in the walls of other ants' nests, just as mice live in the walls of our houses; another quite small species lives apparently on friendly terms with the common large red or horse ant, and may be found running about amongst them, on and in their nests, but, so far as I know, nothing is known as to how its young are reared. There is a curious division in the family between the ants that have true stings and those which have not. The large ants of our fir woods can bite and are able to eject poison through the apical opening of the body into the wound they create, but these as well as the larger and smaller black ants and some others have the sting undeveloped, whereas some of our small species have a sting which they can use with considerable effect; this difference in habit is accompanied by a difference in the structure in the basal segments of the body. In the stingless species the basal segment is reduced {33} [Illustration: FIG. 6] to a flat upright transverse scale (fig. 6, 1); in the stinging ants two segments at the base are reduced to nodes (fig. 6, 3). There is an exception in the case of one little rare genus, _Ponera_, which has only the basal abdominal segment reduced to a scale although a much thicker scale than in the others (fig. 6, 2), and yet which has a distinct sting. These arrangements give the body very free movement so that the tail can be bent forward till it reaches the head. Another curious distinction between the stingers and non-stingers is that the larvae of the former spin cocoons and those of the latter do not; the larvae of _Formica fusca_ occasionally do not do so, but they are an exception to the rule. Cocoon spinning seems to involve the larvae in some difficulties, as without the help of the worker ants they are often unable to extract themselves from their prison. This is a condition which does not, I believe, exist in other groups. In the stingless ants there is a curious difference in habit between the {34} species of the genus _Formica_, where, according to Forel, the workers do not follow in line over unknown ground, and frequently carry one another, the one carried being rolled up under the head of the other, and the species of _Lasius_, where the workers follow one another in line, but never carry each other. Among the stinging ants another method of carrying occurs in certain genera. The porter seizes the one she wishes to carry by the external edge of one of her mandibles and then throws her over her back, so that she lies along the back of her porter with her ventral aspect uppermost and her legs and antennae folded as in the nymph state. Neither of these methods sounds very comfortable, but then probably an ant's idea of comfort and our own may be very different.

Lord Avebury, in his _Ants, Bees and Wasps_, tells us that he has known a male of _Myrmica ruginodis_ live for nine months, although no doubt, as he says, they generally die almost immediately, and he has known queen ants to live for seven years, and workers, which he had in his nest, for six years.

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{35}

THE SOCIAL WASPS

Of these we have only seven different kinds, and with the exception of the hornet they are all very much alike. One often hears people say that they have seen such a large wasp that they think it must have been a hornet, but no one who has ever seen a hornet could mistake a wasp for one. A hornet is _red-brown_ with yellow markings (pl. B, 13), a wasp is _black_ and yellow, and altogether a less formidable-looking creature (pl. B, 14). Even a queen wasp is not so large as a small worker hornet. The hornet nests in hollow trees, our three commoner wasps nest, as a rule, in the ground, but occasionally in outhouses, under roofs, etc. One of the others as a rule makes its nest in shrubs, but occasionally in the ground, another always nests in a bush or shrub, preferring a gooseberry or currant bush, and the only remaining one is a cuckoo of one of the ground species. The gooseberry-bush {36} wasp is not a common species in the south, but in the midlands and north it is abundant. Wasps will eat most things, but are especially fond of syrups and sweets. One species, _Vespa sylvestris_, which seldom enters our houses, is very partial to the flowers of _Scrophularia_ (Figwort). One rarely finds a plant of this in full blossom without finding its attendant wasps. I have seen other species of wasps also visiting it, but _sylvestris_ is practically sure to be there. The diet which wasps provide for their larvae is probably a mixed one, but consists largely of insects. Dr. Ormerod says that a microscopic examination of the contents of a larval stomach shows "the mass to consist of scales, hairs and other fragments of insects, hairs of vegetables and other substances less easy of recognition."