I am not sure if something like this has been done before but the main idea is that after a series of mysterious disappearances in southern India, a group of researchers are called in to investigate. After insects, arachnids, beetles and other various types of bugs of unusual and disproportionate size they discover a SCP - XXXX-1 spider-like crab that is capable of producing and surgically implanting a skeletal structure in different kinds of invertebrates.
The resulting creatures undergo a metamorphosis in which they [a] grow to enormous size to accommodate its new skeleton (e.g. a 2cm caterpillar would grow to a 14 inch length) [b] take on a purely carnivorous diet [c] aggressively defend SCP - XXXX-1. The purpose of this procedure would be for SCP - XXXX-1 (who would survive primarily on the waste product of SCP - XXXX-2+) to control its victims nutritional in take and out take.
Any feed back would be greatly appreciated.