The modes of life of Cerambycid larvae exhibit considerable variety, and much perfection of instinct is displayed by the larvae, as well as by the mother beetles. The larvae of Saperda populnea, are common in certain woods in the South of England in the stems of aspen; they consume only a small quantity of the interior of the stem, and are probably nourished by an afflux of sap to the spot where they are situated. Elaphidion villosum is called the oak-pruner in North America. The parent beetle lays an egg near the axilla of a leaf-stalk or small stem, and the young larva enters this and feeds on the tender material; as it grows it enters a larger limb, and makes an incision within this in such a manner that the wood falls to the ground with the larva within it, the dead wood serving subsequently as pabulum and as a shelter, within which the metamorphosis is completed. The species of the American genus Oncideres are called girdlers, because the parent beetle, after laying an egg in a small branch, girdles this round with a deep incision, so that the portion containing the larva sooner or later falls to the ground. The growth of a Longicorn larva frequently takes more than a year, and under certain circumstances it may be enormously prolonged. Monohammus confusus has been known to issue from wooden furniture in a dwelling-house when the furniture was fifteen years old. Individuals of another Longicorn have issued from the wood of a table, twenty and even twenty-eight years after the felling of the tree from which the furniture was made. Sereno Watson has related a case from which it appears probable that the life of a Longicorn beetle extended over at least forty-five years.[[149]] It is generally assumed that the prolongation of life in these cases is due to the beetle resting quiescent for long after it has completed the metamorphosis. Recent knowledge, however, renders it more probable that it is the larval life that is prolonged; the larva continuing to feed, but gaining little or no nutriment from the dry wood in these unnatural conditions. Mr. C. O. Waterhouse had for some years a Longicorn larva under observation, feeding in this way in the wood of a boot-tree;[[150]] the burrows in the wood contained a great deal of minute dust indicating that the larva passed much matter through the alimentary canal, probably with little result in the way of nutriment.
There are numerous Longicorns that bear a great resemblance in form and colour to Insects to which they are not related. Haensch[[151]] has noticed that species of the genus Odontocera resemble various Hymenoptera, one species being called O. braconoides; he also observed that these Hymenoptera-like Longicorns, instead of withdrawing their underwings under the elytra as beetles generally do, vibrate them rapidly like Hymenoptera. A large number of Longicorns stridulate loudly by rubbing a ridge inside the pronotum on a highly specialised, striate surface at the base of the scutellum, and therefore covered up when the Insect is contracted in repose. A few produce noise by rubbing the hind femora against the edges of the elytra, somewhat after the fashion of grasshoppers. In this case there appears to be comparatively little speciality of structure, the femora bearing, however, more or less distinct small granules. The species of the Hawaiian genus Plagithmysus produce sound in both these manners, the thoracic stridulating organ being beautifully developed, while in some species the margin of the elytra and base of the femora are also well adapted for the purpose of sound-production, and in a few species of the genus there are also highly-developed stridulating surfaces on the hind and middle coxae. This is the only case in which a beetle is known to possess more than one set of sound-organs in the imago state.
Three divisions of this family are distinguished, viz.—
1. Front coxae large and transverse; prothorax with distinct side margins. .......... Sub-fam. 1. Prionides.
2. Front coxae not greatly extended transversely, thorax not margined; last joint of maxillary palpus not pointed, usually broader (more or less) than the preceding joint. .......... Sub-fam. 2. Cerambycides.
3. Front coxae usually round and deeply embedded; last joint of maxillary palpus pointed; front tibiae with a more or less distinct, slanting groove on the inner side. .......... Sub-fam. 3. Lamiides.
The Prionides are on the average considerably larger in size than the members of the other divisions, and they include some of the largest of Insects. The Amazonian Titanus giganteus and the Fijian Macrotoma heros are amongst the most gigantic. Some of the Prionides have a great development of the mandibles in the male sex analogous to that we have already noticed in Lucanidae. The larvae of the large Prionides appear in various parts of the world to have been a favourite food with native tribes, and Lumholz states that they are really good eating. In consequence of the destruction of forests that has progressed so largely of late years these gigantic Prionides have become much rarer.
Several aberrant forms are included in Prionides. The genus Parandra has five-jointed tarsi; the third joint being much smaller than usual, so that the fourth joint is not concealed by it. The Brazilian Hypocephalus armatus was for long a subject of dispute as to its natural position, and was placed by different authorities in widely-separated families of Coleoptera. The structure of this aberrant Longicorn seems to be only explicable on the hypothesis of warfare amongst the males.[[152]] Nothing is, however, known as to the habits and history of the Insect, and only one or two specimens of the female have yet been obtained.
The family Spondylidae has been proposed for some of these aberrant Longicorns, but as it includes but very few, and highly discrepant, species, it is neither natural nor of much use for systematic purposes.
The Lamiides are the most highly specialised division of the Longicorns, and includes the larger number of the species. The front of the head is usually placed at right angles to the vertex, and in some cases (groups Hippopsini, Spalacopsini) it is strongly inflexed, so that the mouth is placed on the under side of the head. The extension of the eyes round the antennae is accompanied by very curious shapes of those organs, and not infrequently each eye is divided into two more or less widely-separated parts, so that the Insect has, on the external surface, four eyes.