Puss Moth Metamorphosis

I’ve photographed puss moth caterpillars (Cerura vinula) before, but this summer I wanted to follow them through all 5 stages, or ‘instars’, of their larval development.

Luckily I discovered a batch of recently laid puss moth eggs by searching the exact same aspen sapling chosen by another adult female the previous year.

6 June: Unhatched Ova

Puss moth eggs (Cerura vinula) on aspen

Cluster of puss moth eggs (Cerura vinula) on underside of aspen leaf

12 June: Hatched Ova

Hatched eggs of puss moth larvae (Cerura vinula)

Hatched eggs of puss moth larvae (Cerura vinula), showing signs of early feeding activity nearby.

12 June: 1st Instar

The ‘puss’ moths look a lot more cat-like at this early stage in their development I reckon.

First instar puss moth larva (Cerura vinula) on aspen leaf

1st instar puss moth larva (Cerura vinula) on aspen leaf. The distinctive tail-like appendages are already present.

1st instar puss moth siblings (Cerura vinula) feeding on aspen

1st instar puss moth siblings (Cerura vinula) feeding on aspen

15 June: 2nd Instar

I’d received a shock on my visit the previous day when I found the caterpillars frozen rigid in position, with their backs arched and tails in the air. They looked decidedly dead and I thought they must have been parasitised. Today, however, they were re-animated once more.

Puss moth siblings sharing the same aspen leaf

Puss moth siblings sharing the same aspen leaf

Puss moth siblings on shared aspen leaf

The puss moth siblings were running out of space on their steadily consumed leaf and occasionally paused to whip their tails furiously at each other.

Second instar puss moth larva on aspen leaf

Close-up of 2nd instar puss moth. The jagged tentacles above the head are very prominent at this stage, unlike in the fully mature larva.

24 June: 3rd Instar

9 days later, after vanishing for several days, the two siblings had relocated further up the branch they originally hatched on. Neither was particularly active in the midday heat.

Third instar puss moth larva resting on silk pad

3rd instar puss moth larva resting on silk pad

Third instar puss moth larva resting on silk pad on aspen leaf

The distinctive saddle patterning of the puss moth caterpillar is much more visible by this stage.

28 June: 4th Instar

It lashed with rain on my next visit and the only visible puss moth was trying its hardest not to get pummeled off the leaf. Its silk pad lashed to the surface provides a firm anchor for feet to grasp.

4th instar puss moth on aspen leaf

4th instar puss moth clinging to wet aspen leaf. The hump on its back is now filling out.

4th instar puss moth larva

At this stage in its development the puss moth’s body has begun to envelop its head and the tentacles appear to have retracted.

9 July: 5th Instar

A further 11 days later I returned to find only one of the original 4 puss moth siblings remaining, now in its magnificent mature larval form.

Fifth instar puss moth larva

5th instar puss moth larva. All the outlandish features of the mature larvae are now present, including the lurid pink face, flagellae and false eye spots.

Fifth instar puss moth larva detail showing extended pink flagellae

Detail showing extended pink flagellae. When threatened the puss moth extends these whip-like appendages from its tail end and waves them around crazily.

To be continued…

Soon after reaching this mature larval stage the puss moth stops eating and leaves in search of a safe place to pupate. Its transformation into the furry white adult moth can then begin. Despite much searching I couldn’t locate any pupae. Next time maybe!

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Raft Spider Life Cycle

Raft spider on pond surface

Raft spider on pond surface

You’d think that arachnids and water was an unhappy combination, but one species of European spider has made boggy ponds their home.

The raft spider (Dolomedes fimbriatus) is the UK’s largest native spider – its body growing up to 2cm long.

It uses the water’s surface like other spiders use their webs – feeling for the vibrations of potential prey with front legs extended. Using this technique it hunts tadpoles, insects and occasionally small fish:

Raft spider eating damselfly

Raft spider eating damselfly

When alarmed, the water repellent hairs on the raft spider’s legs enable it to dive beneath the water, trapping a bubble of air to keep it alive until the coast is clear and it cautiously re-emerges:

The wetland pools favoured by raft spiders are increasingly rare in this country. On the RSPB’s Arne reserve in Dorset their habitat is lovingly preserved, and offers wildlife watchers easy access from the nearby heathland trail:

Boggy pond habitat

Boggy pond habitat

On a good day dozens of raft spiders at various stages in their life cycle can be witnessed at the pond’s edge.

1. Sex

The female raft spider is often considerably larger than the male and mating is a dangerous business. He approaches her cautiously, waving his front legs tentatively to judge her receptiveness:

Male raft spider approaches female

Male raft spider approaches female at her den

She may rush out to scare him off on numerous occasions, after which she retreats and the process begins again, the male edging closer all the while. It’s a nerve jangling thing to watch, let alone participate in.

2. Birth

The female spins a silk bag to contain the fertilised eggs, which she carries about beneath her body, keeping it just warm and moist enough to ensure their survival:

Raft spider carrying egg sac

Raft spider carrying egg sac

Then, when the baby spiders are ready to hatch, she lashes the egg sac to vegetation at the edge of the pond and the tiny hatchlings emerge:

Baby raft spiders in nursery web

Baby raft spiders in nursery web

Mum typically lies in wait nearby to ensure that her young ones don’t come to any harm:

Raft spider guards her hatchlings

Raft spider guards her hatchlings

This phenomenon of hundreds of spiderlings crowded together for their own mutual safety is only really appreciated up close:

Raft spider hatchlings

Raft spider hatchlings closeup

But soon the young raft spiders are large enough to fend for themselves and disperse around the pond.

3. Death

Raft spiders are not fussy eaters. When times are tough and food is scarce, or when too many raft spiders compete for the same local resources, they may even turn to cannibalism:

Not such a pretty sight!

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