Thursday, 21 July 2011

Sexing Lesser Stag Beetles

There appears to be a healthy Lesser Stag beetle population in the neighbourhood. Only in my street, I have come across at least six individuals (unfortunately, two of them had been squished on the pavement) in four years. So far, however, I had only seen females, and I was pleased to find a fierce-looking male this morning. This species is often mistaken with Stag Beetles. But Lesser stag beetles are smaller and uniformly black-grey with fine puntuated bodies. They have strong legs with teeth which they use for digging, especially the females, and, when disturbed, they crouch and retract their legs and antennae under their bodies. Although they are not as easy to sex as the Stag Beetle, males and female Lesser Stat Beetles can be told apart based on several features. First, males have larger mandibles, with a rounded knob on them. Females have two characteristic small bumps on their forehead, between their eyes. The third one is that male heads are wider, almost as wide as their thorax, and therefore their mandibles are also set wider apart. Based on the photos and info I've seen, it appears to be a lot of variation on body size (from 20 to 32 mm) and in knob size in males.
Male

Female
For lots of information about the life cycle of the Lesser Stag Beetle and relatives visit Maria Fremlin's website.

3 comments:

JG Parker said...

Hi

We disturbed a small group of these beetles in our garden (about six) and are a little worried about them. They were in an old plant pot that I thought was just full of leaves and when I upended it, they tumbled out. We made sure they were all upright and covered them with a broken pot but we're worried in case we've disturbed some sort of hibernation process - I know it sounds weird hibernating in summer but my entomology skills are pretty lacking. Can you advise please? Thanks.

Africa Gómez said...

Don't worry too much. A possibility is that they had become trapped in the pot and you actually helped them out. They are quite mobile and can fly, so if you release them they will quickly find a suitable place to hide. I usually release the ones I found on a pile of logs. I think they are more active at night, during the day they prefer to hide.

JG Parker said...

Thanks so much for putting our minds at rest. We'd already moved them to the space beneath our fir tree (very woody and leafmouldy) and sprayed some water nearby in case they needed a drink. Not been out to check on them today, but feeling much better about them. Thanks again.