NZ Gardener

Ruud Kleinpaste

Ruud Kleinpaste on the dastardly garden-decimating deeds of a certain looper caterpilla­r

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Get to know green looper caterpilla­rs

just when you thought it was safe to become a little more relaxed on the pest-control front in your garden, the green looper starts its final generation. And as seems to be customary with this species, the numbers of moths, pupae and caterpilla­rs happen to be at their peak too at this time of the year, whether you’re in Northland or Canterbury.

I’m sure most folk are familiar with this mean, green eating machine. The caterpilla­r is the stage that does the damage to leaves, developing fruit and buds. It can grow to 40mm in length and despite its bright green colour can be difficult to detect as it hides on the underside of leaves during the day.

When these caterpilla­rs are small, they’re absolute masters at camouflage, pressing themselves against leaves. Their main feeding activities take place under the cover of darkness, when they set to work munching holes in leaves and other plant material. On pot plants kept inside, the appearance of frass (caterpilla­r poo pellets) in increasing sizes gives the game away.

The truly remarkable amount of this excrement also gives you some idea about the voraciousn­ess with which these larvae devour your precious plants. Grow coleus, pelargoniu­ms or geraniums, cabbages, chrysanthe­mums or dahlias, and the leaves will disappear before your eyes. The green looper will also gnaw on tomatoes, beans and pip fruit.

I used to keep these caterpilla­rs in captivity so I could observe their curious method of locomotion and watch the incredible way some parasitoid wasps destroy their bodies. Without going into the details of entomologi­cal classifica­tion, it must be pointed out that the green looper is actually not a real “looper” at all, but actually a semi-looper, which adapted a walking style on two widely spaced groups of legs.

At the front, just behind the head, are three pairs of small, segmented legs ending in tiny claws that help to grab onto plant material. Then, towards the end of the muscular and quite powerful body, a few more pairs of nonarticul­ated fleshy lobes act as the hind legs.

This set-up is perfect for creating the looping motion when the caterpilla­r is moving about on the plant. It stretches the front legs out to where it wants to go, grabs onto the plant material, then drags the hind legs up, while the body forms an impressive loop, not unlike the Greek letter omega (Ω).

Once you know what you’re looking for, you’ll be able to find these cute green packages of protein no problem. I catch them as fodder for my selection of captive predatory invertebra­tes; the giant centipedes love these caterpilla­rs, and so do the ground beetles, mantids and tunnel web spiders in my garage.

Out there in “the Nature” (as one of my friends calls the big, bad world of bug eat bug), there’s a tiny parasitoid wasp that punches well above its weight. This minute wasplet uses a clever polyembryo­nic trick to use the whole body of a full-grown green looper caterpilla­r as food for her many babies. All she does is lay a single microscopi­c egg inside a developing caterpilla­r. This egg then divides into two eggs, and the two eggs into four, eight, 16 – you get the picture. Despite all this, the caterpilla­r keeps on eating. In fact, even when all the eggs hatch into protein-obsessed endoparasi­tic carnivores, the caterpilla­r keeps on doing what it does best: creating holes in leaves and fruit. Imagine, with something like 1200 little parasites on board!

It’s in the parasitoid­s’ best interests to keep their host alive for as long as possible, as it’s surely no fun crawling around in decaying caterpilla­r flesh with 1199 closelyrel­ated siblings all competing for the same resources. Indeed, in the first phase of their developmen­t, the wasp babies feast only on nonessenti­al substances (such as fluids and fatty tissues). It’s only when the caterpilla­r starts to spin its cocoon, in preparatio­n for metamorpho­sis into a chrysalis, that the larval wasp parasitoid­s will strike and finish the job.

And that’s what you’re likely to find at this time of the year: a half-finished cocoon with a massively swollen caterpilla­r body inside it, full of hundreds and hundreds of small wasp pupae, bulging out of the skin of that once proud, mean, green gardeneati­ng machine.

Grow coleus, pelargoniu­ms or geraniums, cabbages, chrysanthe­mums or dahlias, and the leaves will disappear before your eyes

 ??  ?? The green looper caterpilla­r ( Chrysodeix­is eriosoma)
The green looper caterpilla­r ( Chrysodeix­is eriosoma)
 ??  ?? Litomastix parasitoid­s feast on their host
Litomastix parasitoid­s feast on their host
 ??  ??

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