The Hymenoptera belongs to one of the most interesting and extensive orders of insects. The structure and habits of the different species which it includes are very various. Their marvellous instincts have excited the admiration and wonderment of the philosophers of all ages. They are, indeed, by far the most intelligent of insects, being greatly in advance of any other group known to exist. The Hymenoptera are mandibulate insects, their mouths being formed for biting, and they undergo complete metamorphoses. Perhaps the most striking external distinctive character is to be found in the structure of the wings, both pairs of which are membranous; and another peculiarity of equal importance is the condition of the prothorax, which is reduced to very small dimensions. In the majority of the Hymenoptera the females are provided with stings, which serve many purposes, independently of weapons of defence. Many families, however, do not possess stings.
Many of the Hymenoptera feed on plants and trees, but probably the greater number are parasitic on other insects.
This order includes the bees, wasps, ants, saw flies, gall flies, ichneumon flies, and many other familiar insects.
The following will show the principal characteristics of each group into which the order has been divided.
Tribe 1, Aculeata.—Generally social insects, consisting of males, females, and neuters. Ovipositor modified into a sting. Larvæ, footless grubs.
Tribe 2, Entomophaga.—Mostly parasitic on the eggs and larvæ of other insects. Ovipositor used as a borer. Larvæ, footless grubs.
Tribe 3, Phytophaga.—Principally vegetable feeders. Ovipositor used as a borer. Larvæ having six or more legs.
TABULAR VIEW
OF THE
PRINCIPAL FAMILIES OF THE HYMENOPTERA.
The Aculeata contains the great majority of the Hymenoptera. Their principal characteristic is that the ovipositor of the female in most of the groups is modified into a sting. The larvæ are footless grubs. This tribe is divided into four sections, which are again subdivided into seventeen families, each of which it is our intention to discuss in their proper order.
Family 1, Aphidæ.—This family contains the numerous species of honey bees which are familiar to all of us. They are very varied in their structure, colours, and habits. Many species are social, while many others are solitary. The common Hive Bee (Apis mellifica) belongs to the former class. There is, perhaps, no insect which has attracted so much notice as this species. Volumes have been written respecting it, and philosophers in all ages of the world's history have spent their whole lifetime in the elucidation of its economy.
In southern Europe, notably in Italy, a much brighter-coloured and finer insect is found, distinguished especially by having yellow transverse bands on the abdomen. This bee was long supposed to be a distinct species, and was described under the name of Apis ligustica, but it is now regarded as merely a variety. This bee has been introduced into all the northern parts of Europe.
Several species of Humble Bees are very common in this country. One of the best known is the Bombus terrestris, the large females of which may attain a length of nearly an inch. This is a large black insect with the extremity yellow.
In another rather smaller species, Bombus lucorum, the extremity of the abdomen is white. Both these species are subterranean bees, forming their nests in banks, etc.
Of the moss-builders, the best known, perhaps, is the Bombus muscorum, the largest specimens of which measure about two-thirds of an inch long.
Another species, Bombus lapidarius, is so called from a preference it shows for making its nests under stones. The end of the abdomen of this bee is bright orange-red.
Of the solitary bees a very common black species is Anthophora acervorum, which is usually found in abundance in the spring in the neighbourhood of banks and cliffs.
The violet Carpenter Bee (Xylocopa violacea), which chiefly inhabits the south of Europe, is a very pretty insect with violet-coloured wings.
The Mason Bee (Chalicodoma muraria) builds its nest, composed of fine grains of sand, very firmly united by a salivary secretion, upon the surface of walls and similar situations. This species has hitherto not been met with in this country.
The Horned Bee (Osmia bicornis) is remarkable for the female having two little horns projecting from the front of her head. This insect usually burrows in sandy banks and cliffs. Another allied species (Osmia hirta) burrows in wood, whilst two others (Osmia bicolor and aurulenta) select ready-made nests in the shells of the common snails (Helix hortensis and H. nemoralis), within the whorls of which they build their cells of gnawed vegetable material.
The Leaf-cutting Bees, which belong to the genus Megachile, are also very interesting in their habits.
Family 2, Andrenidæ.—All the insects belonging to this family are solitary in their habits. The species are very numerous in this country. Many of them burrow in the ground, while others have been observed to make their nests in bramble stick. They are usually smooth, black insects, very unlike bees in appearance. The females have no apparatus for carrying pollen either on the legs or on the abdomen.
Family 3, Vespidæ.—The Social Wasps, which belong to this family, are very well known everywhere in this country. In their general structure they resemble the bees, but are usually much more slender in appearance, and also much less hairy.
The general habits of these wasps are pretty uniform except in the matter of their architecture, and in this respect they display a remarkable variety.
Besides the common Wasp (Vespa vulgaris) two other species found in this country, which build their nests in the ground, follow the same principles in the construction of their nests.
The Hornet (Vespa crabo), which is remarkable for its large size, usually builds its nest in the hollow of a tree. Both the hornet and common wasp sometimes build their nests under the eaves of houses or attached to a beam under the roof; and in these cases the outer covering of the nest is thinner and more delicate in texture than when the dwelling is exposed to the vicissitudes of the weather. Another common species inhabiting Britain is the Wood Wasp (Vespa sylvestris), which builds nests suspended from the branches of trees.
Family 4, Eumenidæ.—One of the commonest and best-known species belonging to this family is the Wall Wasp (Odynerus parietum), which may be almost constantly seen haunting sunny walls during the months of June and July. It makes its burrows in walls and high banks, while many other allied species form their nests in the hollow stems of brambles.
Family 5, Masaridæ.—This family contains the great bulk of the solitary wasps, which, however, are principally inhabitants of warm climates.
The Masaridæ are a small group of black-yellow belted wasps, which are found in the south of Europe, but not in Britain, two of the commonest species being Celonites apiformis and Ceramius fonscolombi.
Family 6, Philanthidæ.—Most of the species belonging to this family are black with yellow spots and bands, and most of them are inhabitants of the warmer parts of the earth. Some of the species provision their nests with beetles and grasshoppers, while others attack bees, and are very mischievous, destroying great numbers.
Family 7, Crabronidæ.—This family includes a considerable number of solitary species of wasps. In colour they are generally black spotted and striped with yellow, but many of them are bright red.
The typical genus Crabro is a very extensive one, including over 150 species, a great proportion of which are inhabitants of Europe, while even Britain possesses more than thirty.
Crabro cribrarius is the largest British species. Its food consists principally of gnats and other dipterous insects. This insect and many others burrow in the ground, generally in hard sandbanks. Another species (Crabro brevis) frequents similar situations, and has been known to provision its nest with small beetles.
Family 8, Nyssonidæ.—This family is not a numerous one comparatively.
Mellinus arvensis is a black insect, about half an inch in length, with stripes on the abdomen and yellow legs. It provisions its nest with flies, and not being able to capture them by swiftness, runs past them when they are resting in an unconcerned manner till they are thrown off their guard, when they are pounced upon and carried off to the nest.
Family 9, Larridæ.—This family very much resembles the last. The species are mostly small insects, few of them measuring half an inch in length. They are usually black, sometimes with the abdomen red at the base.
Family 10, Sphegidæ.—Most of the insects included in this family feed upon grasshoppers, and the manner in which they procure their prey is very curious. In attacking their bulky prey they use every endeavour to turn the grasshopper on its back. When they succeed in this they inflict stings in different parts of the underside of the abdomen and thorax, which soon paralyse the victim, which is then dragged to the nest of the ruthless destroyer.
Sphex flavipennis is a common species in the south of Europe.
Family 11, Pompilidæ.—Most of the species of Pompilus burrow in sand or sandy soil, and store their nests with spiders and the larvæ of insects.
One of our commonest species, Pompilus fuscus, is usually about half an inch long, and is black, with the first three segments of the abdomen red banded with black. This insect makes its appearance in the spring, and may be observed in sandy places throughout the summer. Another common British species is Pompilus punctum, which is black in colour.
Family 12, Bombicidæ.—This small family is not represented in Britain, though found in southern Europe. Many of the insects burrow in the sand, scratching a hole with their forefeet like a dog, as observed by Sir S. Saunders in the Ionian Islands. In the daytime they may be seen flying rapidly from flower to flower, and many of them exhale an odour of roses.
Family 13, Sapygidæ.—This is a small family containing only a single genus, with very few species.
The species of Sapyga occur in Europe and North America. They are supposed to be parasitic in the nests of bees, but the females of the common European species (Sapyga pacca) have been observed carrying small caterpillars, from which Mr. Smith (the great authority on Hymenoptera) justly infers that they are parasitic only to the extent of usurping the burrows made in sandbanks and dead wood by more industrious insects, their own structure not adapting them for the labour of digging.
Family 14, Scoliidæ.—Although this family is abundant in warm climates, we have only two small species belonging to the genus Tiphia in Britain.
They are black, with more or less reddish legs, and measure from a quarter to half an inch in length. In south Europe we meet with several large and handsome species, one of which, Scolia hortorum, is black with two yellow bands on the abdomen.
Family 15, Thymidæ.—The insects of this family are almost exclusively confined to Australia and South America, where they are very numerous. They are generally of a black colour, with more or less extended yellow markings. They are very stout insects; in fact, their bloated bodies give them very little resemblance to any other insects, except perhaps to the Oil Beetles. Very little has hitherto been ascertained respecting their habits, but they are believed to be parasitic.
Family 16, Mutillidæ.—This family includes a large number of species, probably 1,500, but from the differences presented by the males and females, entomologists have found it difficult to arrive at any certainty upon this point. The species are spread over all the earth, but are particularly abundant in warm climates, where also, as usual, they attain the largest size and the most beautiful colouring.
One of the best-known species in our own country is Mutilla europæa, which is about half an inch long, of a black colour, hairy, with the thorax entirely red in the wingless females.
This insect frequents the nests of Humble Bees, and its larvæ appear to be parasitic upon the larvæ of the bees.
Family 17, Formicidæ.—To this family belongs the numerous species of ants, which are social insects, organised after the fashion of the bees and social wasps.
The number of species described is probably considerably over a thousand, but the total number must be very much greater if Mr. Bates is correct in his estimate that not less than 400 species inhabit the valley of the Amazon.
The habits of the ants are most interesting, and one of our greatest living naturalists, Sir John Lubbock, has devoted much of his time in elucidating their economy.
The nests are almost always chambered cavities, hollowed out either in the ground, in walls, and similar situations, or in dead and decaying wood.
One of the commonest examples in our own country is the Garden Ant (Formica nigra), which may be found everywhere in gardens making its nest in the ground.
Another common species is the pretty Turf Ant (Formica flava), which generally haunts commons and heaths, casting up small hills, which serve to throw off the rain; and this species in some localities makes its nest under stones. The Wood Ant (Formica lignipeda) is another familiar species.
A very large group of ants belong to the section Myrmicinæ, the best-known species of which are the Red Ants, Myrmica rubra, and their allies.
A very minute species which has been introduced into this country, probably from Brazil or the West Indies, is the Horse Ant (Myrmica molesta). It is a very small brownish-yellow species, which seems to have been first observed in England in 1828. It takes up its abode in houses, frequently in the neighbourhood of the kitchen fireplace, and when it multiplies becomes such a pest as to render the house uninhabitable. Some of the metropolitan districts have been particularly infested.
Most of the insects belonging to this tribe are parasitic on other insects. The larvæ are footless. There are seven families included in the Entomophaga.
Family 18, Cynipidæ.—This family includes most of the gall flies. The number of species is very considerable. Of the great majority the females pierce with their ovipositor the tissues of plants and trees, and there deposit their eggs, from which the larvæ are soon hatched. The irritation caused by this intrusion of a foreign body into the tissues produces the galls which are so commonly met with.
The galls produced by different species of flies differ greatly in form and structure. Some of them are round and smooth, like fruits, such as the cherry gall of the oak leaves, produced by the puncture of Cynips quercus-foli.
The most singular, however, of all the galls is perhaps the Bedeguar, which is formed on the stems of wild roses by the puncture of a small species, Rhodites rosæ.
Family 19, Chalcididæ.—To this family belong many gall insects, principally found, however, in foreign countries.
The Chalcididæ include a great number of small species, few exceeding half an inch in expanse. Many of these are singular in shape, and others brilliantly metallic; but, owing to their small size, they have hitherto been studied by comparatively few entomologists.
Family 20, Proctotrypidæ.—The Proctotrypidæ are probably much less numerous than the preceding family, but have been less studied, being generally smaller and more obscure in their habits; in fact, some of them share with several beetles the reputation of being the smallest insects.
Family 21, Braconidæ.—This family is one of very great extent.
Many of the foreign species are rather large and handsome insects, often varied with black and yellow.
The best known of the Braconidæ is perhaps Microgaster glomeratus, a small blackish species with reddish-yellow legs, which destroys the larvæ of the common Cabbage Butterflies, round the dead body of which its little yellow cocoons may often be observed.
Family 22, Ichneumonidæ.—The Ichneumonidæ are rather large and slender insects, and are divided into many sub-families.
They are a very numerous group. It has been calculated that nearly 5,000 species have been described, but the data generally are very untrustworthy.
The species of Trogus are rather large insects, measuring an inch or more in length. They are black with reddish legs and abdomen, and the wings are sometimes slightly dusky at the edges.
In another group, Pimplinæ, the ovipositor is generally very long. The best-known species is Rhyssa persuasoria, a blackish insect, which measures about an inch in length. This insect is met with in fir plantations, and uses its extraordinary ovipositor to drill holes in trees infested by the larvæ of Sirex gigas, on which its own larva is parasitic. The insect frequently drives its ovipositor so firmly into the wood of the tree, that it is unable to withdraw it, and perishes in this position.
Family 23, Evaniidæ.—One of the most familiar insects belonging to this family is the Evania appendigaster. It is a small black insect, found in the south of Europe, and is parasitic on cockroaches. An allied British species, Fœnus jaculator, is a not uncommon insect found haunting the burrows of Crabronidæ, upon which it is probably parasitic.
Family 24, Chrysididæ.—The Ruby-tailed Wasps, or Golden Wasps, as the Chrysididæ are popularly called, are among the most brilliant of the Hymenoptera, most of the species being either of an intense green, blue, or fiery red.
They are small or moderate-sized insects, which are found on walls or flowers in the full heat of the sun; for, as a rule, the most brilliantly-coloured insects are diurnal in their habits.
As far as their habits are known, they deposit their eggs in the nests of other insects, chiefly Hymenoptera, on the larvæ of which their own offspring feed.
The commonest British species is Chrysis ignita, which is a very variable insect, both as regards size and colouring.
The insects belonging to the third tribe of the Hymenoptera are strictly vegetable feeders. There are only two families.
Family 25, Siricidæ.—This family includes the insects known as Tailed Wasps. It is not a very extensive family, and its species occur chiefly in Europe and North America, in both of which regions the typical genus Sirex is represented by large species.
The best-known European species which is common in some parts of Britain is the great Tailed Wasp (Sirex gigas), a very formidable-looking insect, of which the female often measures nearly an inch and a half in length.
The general tint is black with the antennæ, the sides of the thorax and the legs and apex of the abdomen yellow. This insect lives in pine and fir woods, and the female deposits her eggs in the woody parts of the trees, into which she bores to a depth of over half an inch by means of her long ovipositor.
Another species which occurs in this country is the Sirex juvencus, of a steel-blue colour, but smaller than the former.
Family 26, Tenthredinidæ.—This is a very extensive family and contains the numerous species of Saw Flies, so called because their ovipositor is in shape somewhat like a saw in appearance.
Probably the best-known species is the Gooseberry Saw Fly (Nematus ventricosus), whose speckled and green larvæ are so injurious in gardens and orchards. This insect is yellowish in colour, and about a quarter of an inch in length.
Tenthredo æthiops, a small black species, deposits its eggs upon fruit trees.
Many other species live on different kinds of plants and trees.