English: Neonaphorura duboscqi with six anal spines from Polden Hills, Street, Somerset, England, United Kingdom.

Original description on Flickr:

Hurray! I've been looking for this one for a while and found two of them today up along Polden ridge, near me. And the coolest thing is that they have six anal spines! SIX! This is a rare one- only three recordings in the UK. And apart from the spines, they do have a very distinctive look, more Michelin man than the other Tullbergiidae I've seen. And they run for cover immediately on being exposed, again- I've not seen this before with this family of soil springtails.

So a question for Frans- why do some springtails have anal spines? What's their purpose? Is having six anal spines a little greedy?

Here's Frans' answer...

Many Collembola species that live in the leaf litter layer or soil layer (edaphic life form) have anal spines (typically in Poduromorpha such as Hypogastruridae, Onychiuridae, Tullbergiidae, Neanuridae, but also in edaphic Entomobryomorpha such as Isotomidae). These species live in crevices and pores of the soil. The anal spines serve 2 purposes:

1. defense system against predators that lurk on them from behind. In the narrow soil pores the presence of anal spines may be sufficient to protect them.

2. anchoring system. The anal spines allow a specimen to anchor itself in the ceiling of the pore/crevice in the soil (e.g. during rainfall the pores may get flooded).

The more the species is adapted to live in the soil (euedaphic species), the more anal spines, 'anal bumps', 'anal ridges' may be present.