Weevils (Curculionidae) form the largest family of beetles (or Coleoptera). Conservatively there are 4000 species recorded from Australia.
Weevils are insects of variable form but linked by an elongate rostrum or proboscis. This has led to their common name of “Elephant Beetles”. Their antennae are on the rostrum in front of the eyes. Their larvae are thick, legless grubs that feed on various forms of vegetable matter.
Some weevils are economic pests that invade foodstuffs including grain. These are usually introduced species.
The Botany Bay Diamond Weevil is a native Australian.
It is a handsome insect about three centimetres long whose colour is predominantly black with patches of metallic blue or green scales. Both immature and adult stages live on Acacias (Wattles). The larvae form tunnels in the trunk and roots of the plant and may be responsible for some of the holes that are drilled in the trunks of Wattles.
The Botany Bay Diamond Weevil is very common in eastern Australia. We often find adult weevils on our Wattles, especially those with bipinnate foliage such as Acacia baileyana (Cootamundra Wattle) and Acacia cardiophylla (Wyalong Wattle). The photo shows a pair mating on the stem of Acacia cardiophylla.
The species has some historical significance. It was one of the first insects collected by Sir Joseph Banks when Captain Cook’s expedition landed in Botany Bay in 1770. Apparently, the Weevil is still common around Botany Bay, south of Sydney.