I first published this story back in April 2015, but decided to revamp it after finding the weevil in the video clip below.
[arve url=”http://oneminutebugs.com.au/wp-content/uploads/2017/08/Diamond-Weevil.mp4″ title=”Diamond Weevil” autoplay=”0″ loop=”yes” muted=”no” /]
This insect is commonly known as a ‘Botany Bay weevil’ (Chrysolopus spectabilis) or by its other common name ‘diamond weevil’. I see these weevils every year but this is the first time I have been able to capture one taking off – albeit on a windy day and only with a mobile phone camera.
Botany Bay weevils belong to an historic group of insects. This weevil was collected by Sir Joseph Banks on Captain James Cook’s voyage to Australia in 1770. Actually we don’t know that Banks himself collected it – it could have been one of his men, or the Swedish naturalist Daniel Solander who accompanied Banks on the voyage. On his return, Banks gave the task of cataloguing his insect collection to the Danish insect taxonomist Johann Fabricius. The weevil was described in 1775, making it one of the first Australian insects described to western science.
Despite it’s common name the Botany Bay weevil is not only found around Sydney, but from coastal far north Queensland to eastern South Australia. The weevil is certainly common in New South Wales and its common name probably dates back to the early colonial days of Botany Bay.
To this day we don’t actually know where Banks’ specimen was collected. Was the weevil collected at Botany Bay in April 1770, or during July/August 1770 when Cook was repairing the Endeavour near present day Cooktown? The label on the specimen simply says “nova Hollandia”.
Banks was no entomologist. He doesn’t mention our weevil in his journal, but does complain about flies and mosquitoes on various occasions, and notes the sighting of a butterfly. He summarised Australia’s insect fauna as: “Of insects here were but few sorts and among them only the Ants were troublesome to us. Musquetos indeed were in some places tolerably plentyfull but it was our good fortune never to stay any time in such places, and where we did to meet with very few. The ants however made ample amends.”
Botany Bay weevils are associated with about 30 species of Acacia. Female weevils chew holes in the stems of Acacia trees at or below ground level in which they lay their eggs. You can see a female doing just that in the image above.
Upon hatching the larvae bore into the stem and usually down into the roots. Adult weevils emerge in the summer, and what spectacular insects they are with their rich metallic green or blue markings on a black background. The adult weevils also feed on Acacia plants in their characteristic manner of removing the leading shoots several centimetres down the stem.
The Botany Bay weevil has a distinctive defence mechanism. One day I was taking some close-up images of weevils on Acacia provincialis when I got just a bit too close for comfort. The weevil suddenly went stiff, toppled backwards and fell to the ground like an actor in a B-grade Western movie. The trick I learned was to move closer to them slowly, taking photos as I went, so they got used to me and the noise of the camera.
Reference: Waterhouse, D.F. (1971). “Insects and Australia”. J. Aust. Ent. Soc. 10 (3): 145–160.