Ha ha, yeah, classic Sheldon, trying to make a joke even though he doesn't really get them! Catatonia is a form of schizophrenia where a patient is unresponsive, just seems frozen, with a blank stare. It's not a classic coma where you lay in bed asleep. You know how Raj reacts to women, just goes speechless? Sheldon is saying that ladybugs must do the same to him, that they turn him catatonic.

"...must send you into a coma."

You could substitute 'make' for 'render' here. 'Render' in this sense means more or less 'to cause to become'. A parallel expression which you often hear is: 'It rendered me speechless' = it was such a shock that it made me speechless. NB 'render' seems to be the word of the day here - another member asked about it early. But back to the 'joke' . My understanding is that if Raj is freaked out by bugs, and freaked out by women, then a 'ladybug' must be a 'double whammy' - a prospect so intimidating as to render him catatonic.