A good start in life

One of the most vulnerable stages in an insect’s life cycle is the egg stage, or when larvae first hatch from eggs. What can adult insects do to ensure their young survive these sensitive stages?

Social insects such as ants, termites, and some bees and wasps are experts at protecting offspring. Their colonies are highly organised with a caste system made up of reproductives (fertile queens and males) and sterile workers. In a colonial structure such as this offspring are produced by the reproductives, and protected within the nest by workers. In other words the entire colony is focused on the well-being of the next generation.

Non-social insects have different strategies. Predatory wasps of the families Crabronidae, Sphecidae and Vespidae either construct mud nests or dig nest burrows. These wasps hunt for an insect or spider to sting and immobilise, then place it in the nest to lay an egg on. The hatching wasp larva will be safe and sound inside a well constructed nest (such as a mud nest), or a hidden nest (burrow), with plenty to eat. Check out this Sphex sp. (Sphecidae) wasp hauling a paralysed locust into a burrow she dug (below).

Locust predator

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Nullius in verba

Last night the Horticultural Media Association of Australia (HMAA) awards night (the ‘Laurels’) were held on Facebook Live. This article “Nullius in verba” won the Laurel in the Technical Category. The article was originally published in 2018 in Hort Journal Australia. Here it is again in its entirety, with some external links that should appear in blue.

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Scientific facts often get lost among all the opinions, ‘alternative facts’, hyberbole, and ‘fake news’ of the digital age. This month’s Pest Files is dedicated to separating the facts from the myths.

Let’s start with something simple – the cabbage white butterfly (Pieris rapae) whose caterpillars are voracious munchers of brassica plants (kale, cabbage, broccoli, etc.). Many gardening magazines and blogs, and even some radio and TV gardening shows, reckon female P. rapae won’t lay their eggs when other females are present. The theory is that these butterflies are territorial and will avoid each other so there is little or no competition between their offspring. To protect your crop all you have to do is place a plastic white butterfly mimic amongst your brassica plants – or so the story goes.

Cabbage white butterfly

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Black Slugs & Bondi Trams

It’s early autumn here in the Grampians in western Victoria which means that it is peak time for some of my favourite caterpillars – cup moth larvae.

Cup moths are found across Australia, and they are members of the moth family Limacodidae. The common name ‘cup moth’ is derived from their cup-like pupae (pictured below). There are more than 100 species found in Australia, in about 25 genera. Larvae have varying tastes depending on the genus involved.

Moth cocoon

The cup moth larvae I find here are in the genus Doratifera and I have only ever seen them feeding on the leaves of Eucalyptus species (although they have been recorded on other plants). The most common species here are the black slug cup moth (Doratifera casta), and the four-spotted cup moth (Doratifera quadriguttata).

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