Lee Kong Chian Natural History Museum

Hymenoptera

Photo credit: Wang Luan Keng
Kingdom:Animalia
Phylum/Division:Arthropoda
Class:Insecta
Order:Hymenoptera

Description

This is a very large order of insects broadly categorised as bees, wasps, and ants, exhibiting a wide variety of forms, habits and behaviour. Hymenopterans may be winged or wingless. In the former, usually two pairs of wings are present. The forewings are usually larger than the hindwings; both are coupled by a row of tiny hooks on the leading edge of the hindwing. Many hymenopterans are wingless in one or both sexes or particular castes. Many species have a constriction between the thorax and abdomen, giving the insect a distinct ‘waist’. In many species, the females have a well-developed ovipositor, which may be modified into a stinger and have modified accessory glands that secrete poison. These insects have biting mouthparts that are used in feeding, capturing prey, constructing nests or in defence.

Controlling the sex of offspring by allowing or withholding fertilisation is found in some species of hymenopterans. In this halpodiploid method of reproduction,males usually arise from unfertilised eggs while females hatch from fertilised eggs. This allows regulation of the sex and population size in large colonies, a strategy associated with a caste system and the partitioning of labour over space and time. While some hymenopterans are solitary, some live in colonies and have a complex social organisation. In these eusocial species, the entire colony functions as a ‘super-organism’. These complex organisations and caste systems are best developed in the ants, social bees and social wasps. The caste system often includes a fertile female (the queen), fertile males (drones) and sterile females (workers and soldiers). The workers perform duties such as building and maintaining nests, gathering food and tending to the queen and nursery (eggs, larvae, and pupae). The soldiers defend the colony while the sole job of the queen is to lay eggs.

Bees, fig wasps, as well as other insects are important pollinators. In their absence, plants and some crops would cease to exist. Ants are important in the formation of soil by mixing and aerating it. They are also significant seed dispersal agents. In Singapore, at least 540 species of hymenopterans have been recorded.

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