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Puss Moth Metamorphosis

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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.

Puss moth larva (Cerura vinula) 5th instar in defensive posture.
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!

Related links:

The Magnificent Puss Moth

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Puss moth caterpillar

The puss moth caterpillar’s ‘eyes’ are only for display

A colleague working for Surrey Wildlife Trust kindly guided me to the location of this wonderful puss moth caterpillar (Cerura vinula) yesterday. A pair of them were contentedly grazing on aspen leaves.

Puss moth caterpillar grazing on aspen

Puss moth larvae feed on poplar, willow, or here on aspen

Colourful character

In adult form the furry grey and white moth flies at night between the months of May and July. The larval form looks much more exotic. The gawdy pink ring around its face gives the puss moth a very distinctive appearance.

Puss moth caterpillar

Head end of puss moth caterpillar

Self defence

If disturbed the puss moth caterpillar extends two whip-like appendages from its tail end and flails them around to deter attackers. It’s a bizarre and unexpected thing to witness.

Puss moth caterpillar tail

Puss moth caterpillar with extended ‘tails’

Puss moth caterpillar tail

‘Tail’ detail of puss moth larva

It also has the ability to squirt formic acid from its thorax if further provoked, but I didn’t try that!

Winter retreat

Shortly before pupation the caterpillar will change to a fetching shade of orange, and then again to purple.

It spins a cocoon of silk around itself and uses bits of tree bark as camouflage to stay hidden for the winter. The resulting cocoon is one of the strongest constructed by any UK moth.

I will have to return to see if I can find it in its various rainbow stages of development.

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