Bug of the Week Vol.5- Botany Bay Weevil

5 July 2024

Did you know that weevils make up the largest beetle family in Australia? Introducing one of the first insects to be documented by researchers in Australia, the Chrysolopus Spectabilis, also known as the Botany Bay weevil. This weevil is also commonly referred to as the “diamond weevil” due to its captivating bejewelled appearance. Perhaps the prettiest out of the 6000 species within the Curculionidae (weevil family) in Australia.

Physical Description

Adult diamond weevils can grow up to 1 inch long, with an elongated rostrum (snout) protruding from its face, and antennae located half way along the snout. Their snouts are curved and thicker in comparison to acorn weevils, which you can find more information about in my first article. Diamond weevils are one of the lucky few weevil species to possess the ability to fly. Their bodies are primarily black with spots that are shades of metallic green and blue, hence the diamond association!

Location

As a Sydney resident, finding out that these captivating creatures live so close to me has left me with no choice but to go exploring to meet one in real life. Once I have completed this mission, I will be sure to report back, but for now, here is the information about their homes that I have gathered to help me on this quest.

The Botany Bay weevil received its name through its discovery in… you guessed it, Botany Bay. This beetle was one of the very first to be documented in Australia by botanist Joseph Banks, who arrived in Australia alongside Captain Cook in 1770. They are primarily found on multiple species of Acacia plants which they feed on around South-East Australia.

Primary sightings of this bug are in national parks, though in the past 5 years multiple have been spotted closer to cities and residential areas. From a sighting in Homebush just last year, to Redfern four months ago, they are truly taking over and I couldn’t be more supportive. My quest should not be too strenuous.

Life Cycle

Female Botany Bay Weevils use their rostrums and mouths to make holes in Acacia plant stems which egg chambers are built in, as well as to reach sap. Up to 20 eggs are laid on the same tree at a time. These weevils choose shorter plants which are close to ground level for their larvae to grow in and eventually drill themselves out of.

Behaviours

Diamond weevils are very nervous creatures, and are bound to have a panic attack when faced with even minor obstacles. Their only documented defence mechanisms include suddenly dropping to the ground upon being disturbed and tightly wrapping their legs around the branch they are on. As biologist Trevor J. Haweswood states, “On January 1984, I collected a large female (diamond weevil) which exuded a very large droplet of a green gut solution through the mouth when handled.” This quote made me laugh but definitely provides a valuable visual and insight into the timid nature of these critters. I believe breathing exercises would heavily benefit the diamond weevil community, starting with box breathing. Inhale for four counts, hold for four counts, exhale for four counts.

My drawing of the green gut solution incident.

Environmental Concerns

Diamond weevils pose a threat for Acacia plants due to their feeding and reproductive behaviours. Larvae destroy plants from the inside by boring their way out of them after hatching. Although this is so, let’s not make them more stressed than they already are, as we know they will simply faint. They are harmless to humans and very pretty so I give them a pass for destroying a few Acacia plants here and there!