Anyone know what bug this is?

[fuzzyoink]

We found this odd looking worm in our garden (in South Africa) about a week ago and I wondered if anyone could please identify it for me.

It seemed as if the worm was either giving birth to live young or something (can be seen at the tail area of the picture), but whatever was coming out of the worm was definitely alive.

Thanks in advance to anyone who can help! ;D

Attachments:

[lepidofrance]

The picture is not so good and it's difficult to see exactly what happens in the tail area. I presume this is a Sphingidae caterpillar (Xylophanes sp. ?) which was eaten from the inside by some parasits emerging before nymphosis.