Another Vapourer encounter

This sunny morning I had to stay at home, as my 7 year old daughter was unwell. On our trip to the doctor I noticed a flying insect I couldn't decide if it was butterfly or moth, it looked like it wanted to settle, so we waited until it did. If finally settled on some railings, flew again and resettled on another part of the railings, and then I realised it was a male Vapourer. This most wonderful of moths! Where there is a male Vapourer settling a female can't be far. Females don't look like moths, they are flightless, their wings reduced to little more than stumps, and they have bulging bodies full of eggs. Females actually move very little in their adult lives, as they just sit on top of their cocoon - which they made as a caterpillar and later emerged - waiting for males to home in their pheromones. Males are a wonderful chestnut colour, a bright moon-shaped white dot on each wing, with feathery antennae, and they fly often during the day.
The male had actually found a female on a corner of the railing and, almost immediately, they mated. I took a few photos with my phone and we carried on.
 On our way back a little later, we checked the railing. The male was gone, but the female wasn't wasting any time, and was busy laying eggs on the remains of her hairy cocoon.

Vapourer caterpillars hatching

I have been keeping an eye on the Vapoureur egg clutches from last autumn every few days. watched a male being attracted by a female just emerged from her cocoon on the windowsill. They mated and the wingless female laid eggs on the cocoon itself. it is thought that the irritant hairs that the caterpillar weaves on the cocoon silk might offer protection to the eggs and young caterpillars.
It has been eight months and the eggs have overwintered and their development has speeded up as the days warmed. Today, in between showers I had a look and noticed nine open eggs and five tiny caterpillars indicating that probably some of them have already dispersed onto nearby plants.
The other egg clutch nearby is showing no signs of hatchlings as yet.

The weird and wonderful Vapourer Moth

While having lunch, a bright, russet moth outside flew against the bay window glass again and again. After a while, I decided to capture it to check what it was. The moth was very unsettled, and carried on flying in the bug pot while we finished our meal. Shortly after, another similarly russet moth, a bit larger, flew against the glass and landed on a silky cocoon on the window frame. I went out and realised the reddish moths were in fact male vapoureurs attracted by a female on the cocoon. The second male was now mating with the female (above). The Vapourer, Orgyia antiqua is a very odd moth indeed. They have a striking sex dimorphism. Males have large, feathery antennae and often fly during the day. They are a rich russet colour with a white spot on each forewing. Females, in contrast, don't look much like moths, they cannot fly as their wings are vestigial, they have small antennae and enormous bulging bodies, full of eggs, and are pale grey in colour. Females will barely move in their short lives, attracting the males with pheromones they release shortly after emerging from her cocoon. The large feathery antennae of the males helps them locate the females quickly.

I took this photo from inside the house.

After mating for about 15 minutes, the male left (13:20). We could then had a closer look at the female. Eggs were visible through her thin abdominal skin. She looks velvety and heavy.

The female quickly started to lay eggs on the cocoon surface, the photo below taken at 15:15. Note that the caterpillar hairs, which are irritating, are embedded on the cocoon itself, so they may act as a defensive device for the eggs themselves.

After egg laying, female dies, so the adult stage is very short, about two days and they do not feed. The eggs overwinter and the caterpillars will be born the following spring.
  There are several British species of a few moth families showing this pattern of female flightlessness, amongst them the Winter Moth. The limited mobility of the females is compensated by the highly dispersive larvae, which might be able to balloon when little. In the UK adults are found from July to September.

On this photo you can see the vestigial wing: just a small hairy flap (the head is down and the abdominal tip up, egg laying).

At 16:41 she had pretty much finished laying.

 I searched around for more cocoons nearby and found one under a wooden shelf by a large cotoneaster, about 2 m away from the first one. It looked very fresh and translucent, and still contained a caterpillar.

The large oval cocoon and large caterpillar inside points to another female will emerge from this one too.

The very surreal caterpillar

Something was eating the young wisteria, but we couldn't spot the culprit, until today. A large, freshly moulted Vapourer Moth caterpillar, also known as Rusty Tussock moth, Orgyia antiqua. Their odd arrangement of hairs and tufts, with neat 'shaving brushes' on their back and tail, and four feathery tufts on a grey-black and red background make it look strange indeed. And if the caterpillar is strange, the adults no less so. Adult male Vapourers are pretty day flying moths, russet coloured with a white spot on each forewing and large feathery antennae. In contrast, females are large, slow moving and flightless as they only have vestigial wings. They don't move far from their cocoon during their short lives, commonly laying their eggs on the cocoon itself. The adults do not feed, but the caterpillars are generalist feeders and use a wide range of bushes, and compensate for their mothers immobility by dispersing widely. I have seen the caterpillars from June to August. After her white bowl treatment, this one was moved to the large cotoneaster, where I have seen them before.

More information
UK Moths page.