This somewhat gruesome looking creature is the grub or larva of an ELEPHANT BEETLE from southern Mexico and central America.  Beetle grubs such as this one are very often found at rest in a distinctive 'C-shape' as shown here, where the head and abdomen are actually touching!

All beetles begin life as a grub, after hatching from an egg.  These are the largest grubs I have ever kept in my collection to date and they will one day turn into some very large beetles, as the elephant beetle is a huge and especially beautiful species with tusk-like horns which provide its common name.  The male grub is the larger of the two and as you can see from the picture below he weighed in at a huge 78 grammes when I bought him in October 2009!

All beetle grubs have a series of openings called spiracles down the sides of their bodies and these can be very clearly seen in the picture below as a series of red oval shapes. 

A spiracle is basically a breathing hole, or an opening through which air is taken into the body.  Each spiracle leads into an air tube called a trachea which carries the oxygen-rich air to the grub's body tissues, and afterwards also carries the carbon-dioxide rich air away from the tissues to be removed through the spiracle!  

The grub's head is the only really hard part of the body, and most grubs have very strong mouthparts or mandibles for chewing through the rotten wood which forms the majority of their diet.  The picture below shows the dark head clearly and you can see the mandibles just below the centre of the picture too.

This grub is certainly large, and here you can see its size in relation to a 10p coin!  Below that is a picture of it alongside a much smaller grub of another species of beetle in exactly the same typical beetle grub resting position!