The Summer Boom in Leaf-Eating Caterpillars

Every summer in Geraldton, people start noticing the same thing:

chewed leaves, tiny droppings on verandahs, curled foliage on eucalypts, odd little cases hanging from shrubs, and entire hedges that look slightly “thinned out” overnight.

No, it isn’t a plague.

It isn’t climate doom.

And it’s rarely something to fear.

It’s caterpillar season - one of the most important quiet cycles in the Midwest’s summer ecology.

Warm nights, dry heat, and bursts of humidity create perfect conditions for the emergence of leaf-eating larvae. These aren’t pests invading our gardens - these are young insects fulfilling their brief, hungry stage before metamorphosis.

And they’ve been doing it long before Geraldton existed.

Here’s what’s happening beneath the leaves.

1. Why caterpillars explode in summer

Caterpillar activity is strongly tied to:

✔ Temperature

Warm nights = faster growth = more feeding.

✔ Humidity spikes

After coastal rain or even sea-mist events, eggs hatch rapidly.

✔ Abundant food

Midwest eucalypts, wattles, and ornamentals put out fresh growth in summer - perfect caterpillar feed.

✔ Bird breeding cycles

Many small birds time their broods around caterpillar peaks.The more chicks that need feeding, the more pressure on caterpillar numbers — a natural balancing act.

Nature sets the clock. The insects just keep time.

2. Who’s eating your leaves? A guide to Geraldton’s usual suspects

🟣 Gumleaf Skeletoniser (Uraba lugens)

Eucalypt specialist.Leaves behind lace-like skeletonised foliage.Common in stands of river gums and red gums.

🟫 Bagworm & Case Moth Larvae (Psychidae family)

The tiny “moving sticks” you see on shrubs?That’s them.They build portable houses from silk, sand, and plant fragments — and chew leaves as they go.

🟩 Chrysomelid Beetle Larvae (Leaf Beetles)

Bright green or blackish, plump, slow-moving.Often cluster on new growth.

🟠 Snout Moth & Web Moth Caterpillars

Create fine silk webs on foliage tips.Often misunderstood as pests, but usually minor feeders.

🟡 Cutworms (Agrotis spp., noctuid moths)

More common inland and in veggie beds, feeding at night.

3. Why caterpillars are NOT bad for your garden

It’s easy to panic when you see chew marks.But here’s the truth:

✔ Healthy plants recover quickly

Most Australian natives evolve with seasonal herbivory.

✔ Caterpillars are a vital food source

Silvereyes, willy wagtails, honeyeaters, bronze-cuckoos — all rely on them to raise chicks.

✔ Natural pruning

Light defoliation encourages fresh growth.

✔ They turn into pollinators

Many become moths or butterflies that pollinate night-blooming or dawn-blooming flowers.

The short-term cosmetic damage is part of a much bigger ecological cycle.

4. This year’s surge - what locals will be noticing

Across Geraldton this summer:

• Gum trees will show more “skeletonised” leaves

• Case moth bags will be more visible on ornamentals

• Garden hedges will be dotted with chew marks

• More moths emerging at night

• Bird activity will be higher in leafed areas

This aligns with:

• warm nights

• late-season humidity

• strong wattle and eucalypt flowering expected this year

Perfect conditions for a boom.

5. A quiet relationship: caterpillars & birds

Each caterpillar is a future meal.

A single nest of silvereyes or honeyeaters may require hundreds of larvae each week to survive.

Without summer caterpillars:

• fewer chicks would fledge

• predators would struggle

• flower pollination would drop

• insect diversity would collapse

Your chewed leaves are feeding the coast.

6. What you should do (and what you shouldn’t)

✔ Do nothing

Let the cycle run. Most plants bounce back beautifully.

✔ Encourage birds

Bird baths, native shrubs, no pesticides.

✔ Leave case moths alone unless heavily infested

They’re part of the natural system.

❌ Do not spray pesticides

Sprays kill everything - including predators, pollinators, and the birds that rely on caterpillars.

❌ Do not remove every affected leaf

You’ll stress the plant more than the larvae do.

7. What this means for the ecosystem

The summer boom in leaf-eating caterpillars is not a problem.It’s a sign of:

• strong plant growth

• good insect diversity

• thriving bird activity

• a functional food web

• seasonal timing working as it should

Geraldton’s summer is harsh, but it is also abundant.If you look closely, you’ll see the hungry, soft-bodied architects beneath the leaves - growing, feeding, disappearing into metamorphosis, and returning as wings.

This is the quiet heartbeat of the season.