NATURE NOTES.

New Zealand Herald, Volume LXV, Issue 20058, 22 September 1928, Page 1 (Supplement)

NATURE NOTES.

BEETLES AS CULTIVATORS. 1 BY J. DRTJMMOND, F.L-S, T.Z.B. Bees, wasps, ants and the termites, or "white ants," dealt with by Maurice Maeterlinck in his characteristic way, are proverbial for their social organisation, rivalling the most highly organised human civilisations, but other insects have their social life. New Zealand has members of a family known as the ambrosia beetle, which, it is believed, show a very definite social organisation by cultivating special fungi, using them as food, and bequeathing them to succeeding generations. They tunnel tho bark of trees. The tunnels, in may cases, radiate from one centre. Each set of tunnels, usually, is the work of the progeny from a single batch of eggs. The only New Zealand species of tho group whose habits have been observed is the ambrosia Platypus, that is, the broad-footed ambrosia. What little is known about it has been disclosed by Mr. D. Miller, of the Cawthron Institute. It is less than a quarter of an inch long. Its legs and feelers are yellow, its head and thorax are light brown, its wingeascs blackish-brown. It has been found boring through bark into the heart of living mountain-beech. Roundish, pearlywhite eggs are laid by the female in the main tunnel. Each grub, as soon as it is hatched, makes a tunnel for itself. Tho fungus it cultivates —if it does so—has a long nome, Lasiosphasrio. This leaves a deep purple sfain on the wood around the tunneil. Another New Zealand member of the family, the kauri Platypus, is believed to cause pin-holes seen in dead kauri trees. The holes are made in living trees. The slender-Platy- ] pus, rtddish-brawn, narrow-bodied, broadheaded, less than a fifth of an inch long, tunnels into living silver pine. It bores through the bark into the tree's heart, leaving at the entrance to the tunnel white accumulations of shredded wood it ejected. Douc's Platypus attacks the sap and the heart of living mountain-beech, and has extended its operations to tho blue-gum. Ambrosia beetles are called ambrosia beetles because in other countries they cultivate fungi that bear the name of the fabled food of tho ancient Gi'eek gods, which conferred immortality on those who used it. Coming down from food for gods to drink for men, there is a species in the Tropics known as Tippling Tommy because it bores' into the staves of beer and rum casks, and makes them leak. The females of two American species prepare fungus beds in pits in their tunnels. The young are no sooner hatched than they begin to eat tho fungus. The mothers are in constant attendance on their young during development. They guard them with care. The mouth of each cradle is closed with a plug of fungus. As fast as it is consumed by the young, the supply is renewed. From time to time, the young clean out their cradles -hygienically, pushing pellets of ejected material through an opening they make in the plugs. The mothers remove the material, and again seal tho openings with fungus. The true ambrosia beetles now aro separated from the Platypus beetles, which have a family of their own, represented by eight species in. New Zealand. A North American species, Platypus compositus, has the walls of its tunnels blackened by the fungus it cultivates. A female of this species often is accompanied by several males. As they are savage fighters fierce sexual contests are frequent. The tunnels are strewn with fragments of the vanquished. Projecting spines at the ends of the wingcases are tho weapons. With them "a beetle attacked in tho rear can make a good defence. By a lucky stroke it may dislocate its enemy's out-stretched neck. The young, wandering along the tunnels, feed in company on the ambrosia that j grows on the walls. Each species of ambrosia beetle, and of Platypus, as far fjs is known, grows its own special fungus in a pure culture. ° Six groups of social beetles, at least four of them, represented in New Zealand, one with no fewer than 152 species, are known. Their food is remarkably diverse. It ranges from dung and wood in different stages of decay to tho living tissues of plants, tho honey-dew produced by mealy-bugs, and delicate fungi. These food-supplies, abundant, but not ■ very nutritious, which the grown-up beetles seek and use primarily for their own consumption, enable them to attain a fair longevity. In each group, the parents show an interest in their young, a much deeper interest than might be expected, and feed them directly, or at least, place them in close contact with food, and guard them. The male helps the female in providing for the young, but. his help may be slight. Unlike ants, bees, and termites, which rank higher than beetles, social beetles have no castes. The earwig is classed as a sub-social insect because the female takes particular care of her eggs, and remains with her young for a time after they are hatched. One female earwig, immediately she had laid her eggs, picked them up in. her mouth-parts, one by one, and wiped them all over. Tho eggs were left clean and glossy. She placer them in a neat pile, and stood guard over them. Some earwigs have refused to touch food from the time they laid until the young were hatched. Others have left their eggs to get something to eat. The web-spinners, a group of insects unrepresented in New Zealand, which make galleries on tho ground or under stones and rocks, are as solicitous as the earwigs. The female takes up her position close to the eggs, and tries to conceal them. She gathers her young about her in the same way as a lieu gathers her chicks. There is so much in common between the highest insect societies and human societies, that matter-of-fact men of science, have failed to detect really fundamental biological differences bctweon them. Real estate, in the form of nests, pastures, and hunting grounds, aro bequeathed by social insects. When weaving tho silken walls of nests, some ants uso their own grubs as shuttles. This is equivalent to the uso of tools by primitive humans. Articulate speech has been developed by humans, but members of insect societies cornmunicato with one another by movements of the body and of tho feelers, by sounds, and by odours. Tho behaviour of ants often is regulated by future contingencies more than by tho needs of the hour. Individual ants may sink their own interests in guarding tho interests of tho community. They may give all their activities, all their aims, al,' : they have, to tho defence of the commun* j ity. completely sinking their individuality, j losing oven the power of feeding a»id I cleaning themselves, and depending for these offices on tho services of slaves. Tho value of communal action is rec g nised to a greater degree by ants and bees than by any other creature in tho world. ■A spirit of self-sacrifice, of service, has raised the higher insects from obscurity and lowliness 'to a position of dominion in which they menace man himself.