Monday, 25 August 2014

Species of the Week: Sexton Beetles

Sexton Beetles (Nicrophorus), also known as Burying Beetles, are fascinating little insects with an amazing life-cycle. They are one of the only insects in which both the male and the female look after their young. These beetles have a level of parental care comparable to birds!

A Common Sexton beetle, Nicrophorus vespilloides

Because they rear their young on the carcass of a small animal, such as a rodent or small bird, it is important that they can detect a dead body. They have sensory organs called chemoreceptors on their club-shaped antennae. These organs can detect the scent of a carcass drifting on the breeze from up to a mile away.
Naturally, a single carcass will attract several Sexton Beetles. The individuals will fight on the dead body, ramming into each other like miniature stags. The males fight other males, and the females fight other females - but the opposite sexes will not fight each other. Eventually, most beetles are driven off, leaving only a single pair left on the carcass.
Straight away, they begin to dig away at the soil underneath the body, creating a hollow for the carcass to fit into. All feathers or fur will be removed from the body, and used to line the hollow. The carcass will be coated in antibacterial and antifungal secretions from the Sexton Beetle's mouth and anus. Finally, the body will be formed into a ball and pushed into the hollow, then covered in soil. This whole process usually takes about 8 hours.
At this point the female usually mates with the male and lays her eggs in the soil around the carcass. However, the female does not always have to mate, as she can fertilise her eggs using sperm collected and stored from a previous copulation with a different male.
The larvae will hatch out and immediately begin to gorge themselves on the carcass. Though they can feed themselves, the parents sometimes help them along a little. They bite chunks off the carcass, then digest it, then regurgitate it for the larvae's consumption. Ready-digested chunks of rotting meat - yum!

Sexton Beetle larva gorging themselves on the rotting, ball-shaped carcass.

It's pretty gross, but you have to admire the parent Sextons, they do a great job of making sure that their offspring have the best start in life. It's not exactly one big happy family, though. If too many eggs hatch, and there's not enough rotting meat to feed them all, the adults will kill some of their own larvae!
Eventually, the larvae will burrow into the surrounding soil and pupate.

An amazing, but pretty gross, life-cycle! I hope that you've enjoyed this week's species. If anybody has any ideas for my next Species of the Week, then let me know by commenting on this post.

Until next time, keep on the wild side!

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