Part 7

It must not be supposed that the limbs of insects are of no value in their identification. We only removed them in order to emphasize the great importance of the character derived from the regional constrictions of the body, which is considered to be certainly one of the most, if not the most, important of any. Besides this character every perfect insect should have six legs, four wings, and various appendages on the head, such as antennae, mandibles, maxillae, labium, etc.; some of these may be so modified as hardly to {128} be recognizable, but they are hardly ever absent altogether; for instance, the two fore wings of a beetle are modified into what are called wing cases, and fold over its back, protecting the two hind wings, which are more or less membranous, as are those of a bee. They have not the functions of locomotive organs, and are used in flight as poisers. Again in the case of a fly, the hind wings seem to be absent, but they are considered to be represented by two little projecting organs which look like large headed pins or nails, but which are quite useless for locomotive purposes.

The organs of the mouth are especially liable to modification, and on these the older authors used to frame their classification. Insects were divided by them, primarily, into two great divisions, viz. those which had a biting and those which had a sucking mouth; treated in this way, the following orders fall into the division with biting mouths:--

_Coleoptera_, or beetles; _Hymenoptera_, or bees, wasps, ants, etc.; _Orthoptera_ and _Neuroptera_, which include the grasshoppers, earwigs, cockroaches, dragonflies, May flies, etc. {129}

And into the division with sucking mouths:--

_Lepidoptera_, or butterflies and moths; _Diptera_ or flies, gnats, etc.; _Hemiptera_, or bugs, including the plant-lice, etc.

These divisions, however, have not been found to be very satisfactory, although very simple when dealing only with the perfect insect stage. In the first place, being framed on this stage only, they are not always applicable to the earlier phases of the insect's life--for instance, although a butterfly or moth has a sucking proboscis, their caterpillars have strong biting jaws, as any gardener well knows. Also bees, wasps, etc., rather upset the arrangement, as they have not only a sucking mouth but also strong biting jaws.

This system of classification has therefore been discarded by most entomologists in favour of that based on the difference between those insects which pass through the distinctive stages of caterpillar and chrysalis on the one hand, and those which emerge from the egg as diminutive likenesses of their parents on the other. In this arrangement, the _Coleoptera_, _Hymenoptera_, _Lepidoptera_, _Diptera_ and _Neuroptera_, fall into the {130} first division, or _Heteromorphae_ as they are called; and the _Hemiptera_ and _Orthoptera_ into the second or _Homomorphae_. The dragonflies are the only slightly discordant elements in this arrangement, as, although their larvae have six legs and walk about under the water and never assume an actual chrysalis condition, still they can hardly be said to resemble their gorgeously coloured parents which fly about so majestically over our ponds, etc.; still this is only one of the many cases which show that nature cannot be held down by any of the arbitrary rules we make for her classification.

The _Hymenoptera_ are therefore characterized and distinguished from other insects by having both a biting and sucking mouth, four clear wings, and by passing through the distinctive liveries of caterpillar or grub, and chrysalis or nymph. It is with this order only with which we have been dealing. To distinguish the aculeate section from the many other forms of the _Hymenoptera_ is too complex a task to undertake here, but the presence of a narrow waist between the thorax and the body, the number of joints in the antennae never exceeding thirteen in {131} the male, twelve in the female, and the presence of a sting capable of ejecting poison in this latter sex, are the most prominent features by which the aculeates may be recognized.

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{132}

ON STRUCTURE

Although in the foregoing chapter a little has been said on this subject, there is a great deal more that a student should learn about the general form of these creatures.

They begin life as white or nearly colourless grubs, which, after various changes of skin, assume what is called the nymph or pupa stage, during which a change occurs, believed to be peculiar to the _Hymenoptera_; the fifth segment of the larval body is transferred to the mass which is called the thorax, so that a portion of what looks like thorax is really the first segment of the abdomen. Continental writers call this portion sometimes the first abdominal segment and sometimes the median segment, but Newman gave it a definite name, the "propodeum", and the most convenient method seems to be to call it so, and treat it as a part of the thorax, calling the first or basal segment of the abdomen {133} that which immediately follows the regional constriction, which occurs between the propodeum and the abdomen.

FIG. 28.

_a_ Head. _a_^1 Antennae. _a_^2 Ocelli. _a_^3 Compound eyes.

_b_^1 Prothorax. _b_^2 Scutum of Mesothorax. _b_^3 Scutellum of Mesothorax. _b_^4 Post-Scutellum of Metathorax. _b_^5 Propodeum.

_c_^1 _c_^2, etc., Segments of Abdomen.

Legs. _d_^1 Coxa. _d_^2 Trochanter. _d_^3 Femur. _d_^4 Tibia. _d_^5 Tarsi. _d_^6 Calcaria or Spurs. _d_^7 Unguiculi or claws. _d_^8 Pulvillus.

_e_ Front wing. 1 Costal nervure. 2 Post Costal nervure. 3 Median nervure. 4 Posterior nervure. 5 Basal nervure. 6 Cubital nervure. 10 1st Recurrent nervure. 11 2nd Recurrent nervure.

_f._ Hind wing. 7 Anterior nervure. 8 Median nervure. 9 Posterior nervure.

Cells. _A_ Marginal. _B_ Upper basal. _C_ Lower basal. _D_ 1st Submarginal. _E_ 2nd Submarginal. _F_ 3rd Submarginal. _G_ 1st Discoidal. _H_ 2nd Discoidal. _I_ 3rd Discoidal. _J_ 1st Apical. _K_ 2nd Apical.

{134} The perfect insect when it emerges has therefore a head, a thorax of four segments, and an abdomen of seven visible dorsal segments in the male, and of six in the female. The [male] has six ventral segments exposed, and often the apex of the eighth, which is frequently elongate, the seventh being almost always short and hidden; the eighth dorsal segment can be discovered hidden under the seventh, but it is very rarely exposed. The head (_a_) bears numerous appendages; a pair of antennae (_a_^1), usually of thirteen joints in the male and of twelve in the female; two compound eyes (_a_^3), composed of many facets; three simple eyes (or ocelli) (_a_^2), which are situated on its vertex; two _mandibles_; two _maxillae_, bearing _palpi_ on each side, of a varying number of joints; and a _labium_, or tongue, which also bears at its base two four-jointed palpi (cf. fig. 20).

The thorax, as we are considering it, consists of four segments--the _prothorax_ (_b_^1), which bears the two front legs; the _mesothorax_ (_b_^2), which bears the intermediate pair of legs and the anterior pair of wings; and the _metathorax_ (_b_^3), which bears the posterior pair of wings and the hind legs. The {135} propodeum has no appendages. The mesothorax above has two parts, a larger portion in front called by some the _scutum_ (_b_^2), and a smaller portion behind called the _scutellum_ (_b_^3). These are separated from each other by a transverse impression, and the scutellum is often raised into a sort of little shield; behind this is another little elevation called the _post-scutellum_ (_b_^4); this is really the dorsal apex of the metathorax, and behind this lies the _propodeum_ (_b_^5). Each leg is composed of various parts, and articulates into a cavity of the thorax called the _acetabulum_. The first two joints of the leg, the _coxa_ (_d_^1) and the _trochanter_ (_d_^2), are very short; then follows the _femur_ or thigh (_d_^3); then the _tibia_ or shin (_d_^4); and finally the _tarsi_ (_d_^5), which compose the foot. At the apex of the _tibia_ are usually two spines called the _calcaria_ (_d_^6). The _tarsi_ are five-jointed, the joints following each other in a linear arrangement, and in the _Anthophila_ the basal joint is more or less dilated; the apical joint bears two claws (_unguiculi_, _d_^7) which are sometimes toothed, and between them, in some genera, there is what is called a _pulvillus_ (_d_^8) or cushion; this is very large and dilated in some of the fossors. {136}

The wing neuration is always rather troublesome, as various authors use different names for the veins and cells. To begin with the anterior wing (_e_), there are four nerves which start from the base and run horizontally; the first of these, which forms the anterior margin of the wing, is called the _costal nervure_ (1); immediately below this, and running almost parallel to it with scarcely any space between them, is the _post-costal nervure_ (2); these end in the _stigma_ (_s_), a dark in-crassation towards the apex of the wing; from the stigma a nerve, curving first downwards and then up to the anterior margin of the wing, encloses the _marginal cell_ (_A_). Below the _post-costal_ nervure, and situated about the centre of the wing, is the third longitudinal nervure called the _median nervure_ (3); behind this again runs the _posterior nervure_ (4), and behind that the actual margin of the wing which is not provided with a protecting nervure, but is only folded back so as to receive the hooks of the posterior wing. Across the wing at, roughly, about a third of its length from the body runs the _basal nervure_ (5); this extends in a somewhat zigzag line from the _post-costal_ to the _posterior nervure_ crossing the _median_, and {137} thereby enclosing two cells, the _upper basal cell_ (_B_) and the _lower basal cell_ (_C_). From the centre of the apical nerve of each of these cells extends a longitudinal nervure; the upper of these runs out nearly to the apical margin of the wing and is called the _cubital nervure_ (6); this is united to the nervure of the _marginal cell_ by one, two, or three cross nervures, enclosing thereby one, two, or three cells called the first (_D_), second (_E_), and third (_F_) _submarginal cells_. The nervure from the lower basal cell is a short one, as it is met by a cross nervure called the first _recurrent nervure_ (10), which runs from the _cubital_ to the _posterior_, thereby enclosing two cells, the first (_G_) and second (_H_) _discoidal_. The _second recurrent_ (11) leaves the _cubital_ nearer the apex of the wing than the first, meeting a nervure which, springing from the outer posterior angle of the second discoidal, closes the third discoidal (_I_), and, curving slightly upwards, nearly reaches the apical margin of the wing. Beyond the second recurrent, and behind this last nervure which we have been talking about, are two spaces not actually enclosed, but called the _first_ (_J_) _and second_ (_K_) _apical cells_.

The posterior wings have very few cells. {138} Like the anterior pair they have three longitudinal nervures; the _anterior_ (7), which runs close and parallel to the anterior nerveless margin, and often touches it at about half the length of the wing; the _median_ (8) and _posterior_ (9) run in diverging lines from the base towards the exterior margin of the wing, the anterior and median nervures being almost always joined by a cross nervure, and the median usually united to the posterior by a cross or curved nervure. The actual base of the anterior wing is covered by a little convex somewhat shell-like cap, called the _tegula_ (_T_). The abdomen is composed of a series of segments in linear arrangement (_c_^1 _c_^2, etc.). These call for no special remark, beyond what has been said in the chapter on males and females, but those who wish to investigate the very interesting questions connected with the terminal segments of these creatures should consult some more technical work.[3] The arrangements of the mouth parts and of the apical segments of the Hymenoptera afford perhaps the most important structural {139} characters of the order, but they involve an amount of dissection and study which can only be undertaken by those who are inclined to give themselves up to this subject as a speciality.

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{141}

INDEX

Abdomen, 125 Acetabulum, 135 Ammophila, 22 Andrena, 9, 12, 15, 48, 77, 79, 122, 139 -- fulva, 121 -- rosae, 138 -- thoracica, 121 Antennae, 101, 103, 134 Anthidium, 50, 121 Anthophila, 6 Anthophora, 48, 61, 82, 93, 109, 111, 121 -- pilipes, 61 -- retusa, 62 Ants, 28, 31, 88 Aphides, 88 Apis, 16 Astatus, 103

Banded bodies, 120 Beetles, 20 Biting, 3, 32 Black Species, 120 Bombus, 16 -- terrestris, 41, 42 Brain, 125 Bramble Stems, 12 Breeding, 113 Broods, 13 Burrows, 9

Calcaria, 70, 135 Carder Bees, 40 Cardines, 75 Carpenter bee, 55 Caterpillar, 19, 20 Cells, 10, 12, 28, 29, 40, 58 -- hexagonal, 28 -- pitcher-shaped, 58 -- waxen, 29, 40 Ceratina, 47, 128 Chimneys, 25 Chloroform, 118 Chrysis, 27 Cilissa, 48 Cleaning hairs, 68 Clover fertilization, 39 Cockroaches, 128 Cocoons, 33, 58 Coleoptera, 128, 129 Colletes, 44 Colonies, 5, 63 Colour, 100 Colour schemes, 22 Combs, 23, 68, 69 Corbicula, 67 Coxae, 135 Crabro, 95, 102 -- albilabris, 119 Cuckoos, 3, 14, 30, 54 -- flight of, 85 Cyanide, 116

Dasypoda, 48 Development, 124 Digestion, 125 Diggers, 6, 7 {142} Diptera, 129 Distribution, 105 Domestication, 41 Drone flies, 3 Dufourea, 106

Earwigs, 128 English names, 55 Epeolus, 45 Ether, 117 Eyes, 134

Females, 95 Femur, 135 Figwort, 36 Figure of insect, 133 Flies, 3, 129 Flower lovers, 6 Flute, 57 Food, 6, 28 Foot, 135 Formica, 34, 59 -- fusca, 119 -- sanguinea, 89 Formicoxenus, 96 Fossors, 6, 7

Galleries, 28 Grasshoppers, 19, 128 Growth, 126 Guests of Ants, 89

Hairs, 65, 71 Halictus, 13, 15, 17, 77, 94, 97, 119, 122 Head, 125 Hemiptera, 129, 130 Heterogyna, 28, 31 Heteromorphae, 130 Hive bee, 2, 16 Homing instinct, 21 Homomorphae, 130 Honey pots, 29 Hornets, 35 Humble bees, 39 -- mutilated, 41 Hymenoptera, 128, 129

Ichneumons, 21 Inquilines, 3

Jewel flies, 21, 27

Keyhole wasps, 101 Killing bottles, 126 Knife-like hairs, 68

Labels, 118 Labial palpi, 5 Labium, 127, 134 Larva, 11, 13 Lasius niger, 91 -- flavus, 91 Latin names, 55 Lawn bee, 9 Leaf-cutting bees, 52 Lepidoptera, 129 Ligula, 75, 134 Limbs, 125, 127 Locomotion, 125 Lodgers with ants, 89 Lomechusa, 89 Long-horned bee, 104 Lora, 74 Lysimachia, 106

Macropis, 106 Males, 95 Male wasp, 2 -- hornet, 2 Mandibles, 127, 129 Mason bee, 55 Maxillae, 75, 127, 134 Mayflies, 128 {143} Melecta armata, 61 -- luctuosa, 62 Mentum, 74 Metoecus paradoxus, 38 Mimicking flies, 94 Miscophus, 119 Moss, 29 Mouse's nest, 29 Mouth, 128 Mutilla, 112, 119 Myrmica, 34 Myrmosa, 100

Nests, 24, 26, 31, 35, 45, 49 -- in bramble stems, 45 -- Humble bees, 40 -- of leaves, 53 -- of paper, 37 -- in wren's nest, 41 Neuration, 136 -- figure and explanation of, 133 Neuroptera, 128, 129 Nodes, 33 Nomada, 15, 48 Non-predaceous hymenoptera, 3 Nymph, 11

Odynerus, 24 Orthoptera, 128, 130 Osmia, 48, 56, 120 -- bicolor, 59, 121 -- inermis, 58 -- leucomelana, 57 -- parietina, 58 -- rufa, 56 Ovaries, 4 Ovipositer, 1 Oxybelus, 86

Palm, 82 Palpi, 134 Panurgus, 49 Paper, 37 Paraglossae, 76 Paralytics, 18 Plant lice, 19 Poison bags, 1 Pollen collecting, 65 Pompilus, 87 Ponera, 33 Porterage, 34 Post-scutellum, 135 Predaceous species, 3 Preservation, 116 Propodeum, 132, 135 Prosopis, 44, 46 -- cornuta, 47 Pulvillus, 135

Queens, 4

Rarity, 105 Ray, John, 63

Sallows, 82 Sandy bank, 83 Saropoda, 93, 111 Scale, 33 Scrophularia, 36 Scutellum, 135 Scutum, 135 Segments, 96 Setting, 117 Sexual structure, 100 Shin, 135 Snail shells, 12, 57 Social species, 3, 4, 28 Solitary species, 3, 4, 6 Spade-like hairs, 69 Sphecodes, 13, 15, 17, 48, 97, 122 Spiders, 19 Stinging, 2, 38 Stings, 2, 32 Stipes, 74 {144} Straws, 12 Structure, 132 Stylops, 77 Submentum, 74 Swarming, 29

Tarsi, 135 Tegula, 133, 138 Thigh, 135 Thorax, 125, 129 Tibia, 135 Tomtit, 42 Tongues, 15, 39, 44, 49, 66, 72 Trochanter, 135 Tubular entrance, 25

Unguiculi, 135

Vagaries of structure, 104 Velleius dilatatus, 38 Vespa sylvestris, 36

Walls, 12 Wasps, social, 35 -- solitary, 24 Waspy coloration, 120, 121 Wings, 110 -- cells, 112, 133 -- folded, 24, 28 -- hooks, 110 -- nervures, 133 Workers, 4 Wrens' nests, 41

Yellow-coloured species, 120

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NOTES

[1] In this case, only the actual tongue (or _ligula_) and its _paraglossae_ are figured.

[2] _The Guests of Ants and Termites_, by E. Wasmann, S. J., translated by H. Donisthorpe, F.Z.S. (_Ent. Record_, Vol. xii., 1900.)

[3] cf. _Transactions of the Entomological Society of London_, 1884, p. 251 et seq.: Hymenoptera Aculeate of the British Islands, etc.

End of Project Gutenberg's Wild Bees, Wasps and Ants, by Edward Saunders