Bug of the Week: Geotrupes spiniger

bug_geo

This week’s bug is Geotrupes spiniger, but from this picture – it is equally likely this species is Geotrupes stercorarius. Insects that look superficially the same, can be completely different species. This is certainly the case with spiniger and stercorarius. 

To differentiate the two species, there are a couple things you can check.

If you flip the beetle over onto its back – you will see many hairs on its abdomen. In the case of Geotrupes spiniger – the hairs will be quite sparse, or absent along the middle of the abdomen. In the case of Geotrupes stercorarius, the hairs are more or less constant across the middle.

Spiniger_Sterco

If you’ve got an even better eye, you can check out the mandible – Geotrupes spiniger has an additional distinct lobe. I personally find this character more difficult to see than the abdominal hairs. [UPDATE: Darren Mann has provided the helpful image below to clearly show the differentiation in mandible shape between the two species – noting it can be difficult in older individuals – Thanks a million Darren!]

spin-sterc_heads

If you happen to find this species when you’re out and about, take a photo and submit it to Team DUMP‘s ongoing  effort of monitoring dung beetles across the UK.

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