June 2017

A maggot’s tale

We found these strange-looking worms in a bucket of water where we were soaking palm fruits at our plant nursery. What are they and how did they get there?

Rat-tailed maggot of the Green Hoverfly (Austalis copiosa) seeking place to pupate.
Video courtesy of Colleen Foelz.

Answer

Adult Green Hoverfly (Austalis copiosa). Image courtesy of Colleen Foelz.Episyrphus viridaureus - the adult pollinates flowers and larvae feed on aphids, making this species of hoverfly beneficial in gardens.Episyrphus viridaureus - the adult pollinates flowers and larvae feed on aphids, making this species of hoverfly beneficial in gardens.Your little wormy-looking creatures are the aquatic larval stage of an insect called a hoverfly. An adult hoverfly must have laid her eggs in the water that was soaking the palm fruits.

 

The larvae of this hoverfly species, Austalis copiosa, are called rat-tailed maggots. The ‘tail’ is actually a tube that acts like a long snorkel which allows the maggot to breathe while living in stagnant water; the type of smelly water you sometimes find in drains and gutters. The tube is telescopic and can be many times the length of the maggot when fully extended.

 

After a time the maggot stops feeding and seeks out a dry spot for the next stage of life, the pupa. That’s what the one in the first video is doing. Over the following weeks it metamorphoses (changes) inside the pupal case until it emerges as an adult Green Hoverfly (see video of one ‘grooming’). It flies away to feed, mate, lay eggs and start the cycle again.

 

Worldwide there are thousands of species of hoverfly, with over 150 in Australia. They belong to a family called Syrphidae (often referred to as syrphids). Some hoverflies mimic wasps and bees as a defence against predators.

 

The syrphids can be broadly grouped based on the feeding behaviour of their larvae. Some larvae are predacious and feed on plant-sucking pests such as aphids or thrips; others (such as the rat-tailed maggots) feed on rotting vegetation, and the third group live in ant nests. Adult hoverflies are all pollen and nectar feeders, hence their importance in pollination.

 

Most of us would prefer not to encounter maggots in our kitchens, gardens and gutters but they are vital clean-up agents that help to break down materials such as dead animals, rotting vegetation and dung. Their feeding activity changes these materials into forms that can be reused by other living things.

 

 

Green Hoverfly (Austalis copiosa) grooming. Video courtesy of Colleen Foelz.

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