Oak Eggar Moth Study

Little Bear loves bugs, beasties and all sorts of creepy crawlies. Much of his time has been spent capturing specimens to draw, discuss and release, and he enjoys taking care of the creatures he finds. One of the most anticipated events of our year is the arrival of Painted Lady caterpillars from Insectlore, and he loves to observe their transformation, drawing and even making a book about them. He has also caught and kept Large White caterpillars from the garden, as well as worms, ants (NOT my favourite!) and snails.

This June, our neighbour found a massive fuzzy caterpillar, and of course immediately thought of Little Bear. And of course he had to keep it. A bit of Googling, and we discovered that it was an Oak Eggar moth larva, which had probably been munching on the brambles that our neighbour is fighting an ongoing war with in her garden.

We installed it in our butterfly net, added a pile of fresh bramble leaves, and watched it march round and round at speed. It ignored the leaves completely, and my research seemed to suggest it was at full size, so I wondered if it was looking for a good place to pupate. This turned out to be correct, as that evening it settled down under some leaves and went very quiet. It took a couple of days to make it’s pupa, and was settled there for a few weeks.

20160724_164528Unfortunately, I didn’t manage to get a good picture as it was so tucked away and I didn’t want to disturb it too much. However, this is the cocoon after the moth had hatched. We plan to put it under the microscope next week, and compare it with an empty chrysalis from this year’s Painted Lady butterflies.



Little Bear lost interest a bit at this point. We had a few events to attend, and life became much more exciting than a pupating caterpillar. I made sure to check on it every day, however, and so I was the first to notice when it hatched. We missed the actual emergence unfortunately, and found the moth resting quietly on the side of the net. She was a lovely, plump, fluffy creature, who looked soft enough to stroke, although we didn’t for fear of damaging her wings.

moth size

A bit more Googling told us that this was a female moth, and that she would sit still, releasing pheromones for the males to pick up with their comb-like antennae. The males would then come to her to mate. As an experiment, we decided to hang the net up in the apple tree and see if we could attract a male moth. It was a warm afternoon, and we didn’t need to wait long. within half an hour, a male was fluttering around the net, trying to get in to the female. Little Bear immediately noticed they were much darker in colour, and we could see their antennae were thicker than the female’s, for picking up her pheromones. We counted four males visiting over the next two hours, before it was time to go in for tea.

That evening, Little Bear and I talked about how moths, like butterflies, are important to our world, and that it was important to make sure this moth had the chance to make as many eggs as she could. We decided that the next day we would take her outside again, and this time let a male moth into the net so we could see them mate, then release both into the garden.

That is exactly what we did. Less than half an hour after taking her outside that afternoon, there were three males fluttering around her. They were not still for a moment, trying their hardest to find a way in, and getting tangled up in our slightly too long grass.

In these pictures, you can see we had put some fruit for our moth into the net, but she did not try it or even move from her position on the side of the net. We later discovered that Oak Eggar moths do not eat, and do not have real mouth parts. They survive completely on the fat left over from when they were larvae, and so do not live for more than a few days. Little Bear was sad about this, and felt this made it even more important that we released our moth so she could lay lots of eggs and make more moths.

We opened the net, and helped one male moth get in. He found her straight away, and at last stopped moving long enough for us to get a proper look at him. He climbed onto her back, then flipped under her wing and attached himself to her.

She still did not move at all, and the other male moth outside the net continued to flutter around for a few moments, before he flapped away. This was the best picture I managed to get of the pair attached, you can just see they are joined at the base of their abdomens. You can also see how massive the female’s abdomen is compared to that of the male. She really was big!

The two moths remained like this for a good twenty minutes, until Little Bear began to wonder if they would ever finish! I took advantage of the time to get as many close up pictures as I could. It was a bit tricky manoeuvring my phone inside the net, but I think I did quite well!

At last it was all over. The male shivered his wings, then fluttered out and away across the garden. The female remained where she was for the rest of the afternoon, still not moving at all. We began to wonder if she would ever fly away, but when I went to fetch the net in after the small bears had gone to bed, she was gone. I’m a bit disappointed that I missed seeing her fly, but we are glad that she has gone to make lots of eggs and caterpillars.

Raising caterpillars is one of Little Bear’s favourite things to do, and he learns so much about the process from actually being able to watch it. This experience taught us both so much about a moth’s reproductive cycle, and raised lots of questions about how eggs are made and fertilised. It really is fascinating.


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