Tomato fly – revisited

An email conversation with an entomologist from New South Wales prompted the addition of a paragraph (in bold) to this article from about a year ago.

I picked a tomato off the bush the other day and noticed a little hole in it. I cut it open and saw that the contents were looking a bit ordinary, as if it was about to rot. Under higher magnification I could see the culprits – fly larvae – yep, maggots! The image below shows a close-up of one.

tomato fly larva

Queensland fruit fly (Bactrocera tryoni) and Mediterranean fruit fly (Ceratitis capitata) are known to lay their eggs in tomatoes, but neither of these species is found in my region of Victoria. The larvae of vinegar fly (Drosophila melanogaster) – known in America as “fruit fly” – feed in fallen rotting fruit, but this tomato was on the plant. So what species of fly produced the larvae?

I put the offending tomato in a plastic container and waited. Over a few days the larvae grew bigger, allowing me to take the photograph above, and started to jump around the container. I knew this was a sign the larvae didn’t want to be in the moist tomato pulp anymore, and were looking for somewhere dry to pupate. I shepherded as many jumping larvae as I could into a dry container with some tissue paper at the bottom, and by the following day they were all pupae.

The flies haven’t emerged yet, but I know what species they are because I went through this same exercise last year. Behold, the metallic-green tomato fly Lamprolonchaea brouniana (Diptera: Lonchaeidae).

metallic green tomato fly

These little flies are only about 4mm long, so they might be a bit hard to see in the garden. The good news is that, in my garden anyway, they are not in very large numbers and don’t lay eggs in every tomato. It is an endemic species that has been most commonly collected from the temperate south. Those wanting to learn more about this pretty little fly could jump onto the Australian Fauna Directory here.

(Note – The “jumping” behaviour of the larvae of these flies is not unique. Queensland fruit fly larvae also “jump” when they leave the larval substrate to pupate. My NSW correspondent suggested that this has led to some confusion in Victoria where people are assuming these metallic-green tomato fly larvae are Queensland fruit fly larvae. Then they wonder why their Queensland fruit fly traps and baits, which are specific to QFF, aren’t working. This illustrates why accurate identification is vital in pest management.)

One more thing about the vinegar flies mentioned above. Don’t be alarmed if you find lots of little flies in your compost. Vinegar fly larvae help with the decomposition process. You don’t need to “get rid of them”! Vinegar flies are about 3.5 mm long and look like this (below).

drosophila

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What’s good about ants? Plenty.

Many people, especially gardeners, only see ants as pests, but they couldn’t be further from the truth. These days I work weekends in a garden centre, and when summer arrived every second customer I encountered wanted a product to kill ants. One person even asked me for the “Agent Orange” of ant insecticides! They were somewhat bemused when I asked “What sort of ants are they, and why do you want to kill them?”

ponerine ant
This harmless ponerine ant is holding a water drop in its mandibles.

There are more than 1,300 described species of ants in Australia, but only a minority are considered to be pests. Most ant species are beneficial in some way. Ants are extremely important in the environment and are sometimes referred to as ‘ecosystem engineers’. For example, in bushland, ants are vital dispersers of seeds, a mutually beneficial practice known as myrmecochory. Many Australian plants, about 1500 species or so, have evolved to produce seeds with elaiosomes, which are expendable seed parts containing oil, protein, starch, sugar and vitamins. Ants collect the seeds, and carry them off to their nests underground. However, they only eat the elaiosomes and discard the rest of the seed in a ‘rubbish tip’ section of the nest, or hide them under leaf litter outside the nest. The seeds are then sort of planted, safe from predation or fire, where they can germinate safely.

Mind-boggle alert! Some stick insects exploit these ants’ seed-burying behaviour by laying eggs that look like seeds (see below), and even have an expendable fatty part for the ants to feed on. The eggs are collected by ants and taken into their nests where they are safe from predators. When the young stick insects (nymphs) hatch they even look and smell like ants. The nymphs then wander out of the nest, past the unsuspecting ants, and up the nearest gum tree to feed on the leaves.

Phasmid eggs

Anyway back to the ants. Ground-dwelling ants aerate the soil while digging their nests, which allows water to penetrate the soil more effectively. Those ants that make their nests in dead wood aid the decomposition process of that wood. Many ant species are predators or scavengers consuming vast numbers of the eggs, larvae and adults of insects and other invertebrates − either dead or alive. Ants in turn are food for many creatures such as birds, echidnas, reptiles and other invertebrates.

Some common ant species that are predators and scavengers include funnel ants (Aphaenogaster spp.), green tree ants (Oecophylla smaragdina), meat ants (Iridomyrmex spp.) and sugar ants (Camponotus spp. – pictured below). These ants should be encouraged and respected rather than bombed with insecticides.

camponotus

Where I live in Western Victoria there is really only one ant species to be wary of and that is the Jumping Jack ant (Myrmecia pilosula) pictured below – aka Jack jumper, hopper ant, skipper ant. Jumping Jack ant stings can cause anaphylaxis, a life-threatening condition in some people typified by constriction of the throat and difficulty in breathing. Milder symptoms include swelling and itchiness around the wound. They are extremely aggressive ants by nature and move in a characteristically jerky, jumping manner. Their movement may look a little comical, but there is nothing funny about the sting!

jack jumper ant

In a future blog post I will be writing about how some butterflies have interesting associations with certain ant species. In some cases the butterflies are totally reliant on the ants for their survival.

 

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Tomato fly

I picked a tomato off the bush the other day and noticed a little hole in it. I cut it open and saw that the contents were looking a bit ordinary, as if it was about to rot. Under higher magnification I could see the culprits – fly larvae – yep, maggots! The image below shows a close-up of one.

tomato fly larva

Continue reading Tomato fly

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Fear and loathing

It happened one day at primary school back in the 1960’s. “It’s biting me, it’s biting me!!” the boy screamed as he sprinted past me. He then collapsed on the ground in flamboyant B-grade movie style, shrieking loudly. I ran up to him and could see the culprit clinging to his leg, a very large but harmless moth which I now know it to be one of the ‘rain moths’ of the family Hepialidae (below).

Trictena atripalpis Continue reading Fear and loathing

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Gall-inducing insects

Have you ever noticed strange lumps and bumps on the leaves and stems of native plants? Galls are especially common on gum trees and wattles, and they are abnormal plant growths that form in response to invasion of plant tissue by a variety of organisms. Galls can be caused by certain species of wasps, flies, beetles, psyllids, coccids, thrips, moths and aphids, as well as by nematodes, mites, bacteria or fungi. This post concentrates on some common gall-inducing insects found in Australia. Continue reading Gall-inducing insects

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Night of the Bloodsuckers (Part 2)

Night of the Bloodsuckers (Part 1) prompted several conversations, and people had lots of suggestions about how to control or repel mosquitoes. The repellent suggestions included lemongrass, citronella, and garlic oil spray (a product not available in Australia as far as I know). In addition to emptying pot trays, bird baths etc regularly to stop mosquitoes breeding, one correspondent reminded us not to forget emptying bromeliads. One ingenious person suggested deliberately placing buckets of water around the garden to encourage mosquitoes to lay their eggs in them, and then emptying them out. That’s using buckets as a trap! Thanks for all your suggestions.

dead mosquito Continue reading Night of the Bloodsuckers (Part 2)

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