Herald the heralds

Will you spot a hibernating herald this autumn-winter...

A few Septembers ago I visited a gully and cave complex in Shropshire and I ended up in a particularly dark spot. I rootled around for my phone, flicked on the torch and happened to glance above me. Resting on the ceiling were several herald moths and cave spiders. I forgot to continue on my journey and started to pay attention to what I'd previously missed!

I was fascinated. Cave spiders live in dark places like this but what were the herald moths doing? Was this just a great place to spend the day for these nocturnal moths because, surely, it was too early to hibernate (or go into diapause, as it's called in insects)? It seems not! A survey of herald moths in Scotland has shown that the moths start to arrive at their overwintering sites in late July, with the peak arrival in September. This same study has shown that once they settle in, they remain in that very same spot until the end of March/April the following year.

Two herald moths hibernating on the white egg sac of a cave spider

I knew nothing of this survey until fairly recently when I read an article by two naturalists and herald-fans, Katty Baird and Mark Cubitt, in British Wildlife magazine. Their write up of the last 10 years of surveying answered all my questions. Highest on that list had to be "just how dangerous is it to hibernate next to cave spiders?" Judging from their research, it's not as dangerous as you might expect. It turned out that once the moths were completely stationary, they were pretty much ignored by the spiders. It's not until they started to wake up and leave that some were caught in the spider webs. However, I'm not sure I fancy the chances of the two moths snoozing on the spider egg sac (see photo). The spiderlings hatch in late winter/early spring and I'm fairly certain they'd be more than happy to find breakfast already served!

Four herald moths are hibernating, resting on a cave roof. They're orange/bronze in colour.

Adult herald moths are beautiful creatures. It's thought that the name derives from their unusual shape, with scalloped edges to their forewings, which resembles the traditional tabard of a herald. The colours are shades of bronze, russet and grey, marked with cream lines and with flame-like patterns reaching from the centre of their forewings towards their furry heads. They're relatively widespread with their green caterpillars feeding on willows and poplars so even if you don't catch sight of an adult, you can always look for their caterpillars in spring.

Since that first sighting in Shropshire, whenever I visit places with dark tunnels or other such hidden places (castles are good for this), I pop on the phone torch and search for heralds and spiders. It's not often I find either but it's a special day when I do. If you're following in my herald-searching footsteps, it's important not to hang around too long so that your presence doesn't change the temperature and disrupt the diapause. These dark places are also loved by bats and although I've never spotted one, I know that if I do I need to turn off the light and move on as quickly as possible to avoid disturbing them too.

The survey in Scotland, which started as a survey to find a different moth species altogether, has been running for 10 years and has seen over 130 people submit sightings of over 25,000 heralds. This is a staggering result, which has exploded knowledge of abundance and distribution across Scotland and just shows the importance of recording the wildlife that we see. Our Wildlife Sightings project has been running since 2020 and has received over 3000 sightings of wildlife across Worcestershire; I wonder whether we'll receive any herald moth records this autumn and winter?!