[ECOLOG-L] Marking histerids - Please help

[Bonaventure Omondi Aman]

Dear Colleagues,
Do you know any products that would be used in marking tiny black histerids
(1.5mm long)?
I need to do mating studies between populations of these insects, which I
cannot sex visually, so I have to pair them randomly hoping some will end up
with potential mating partners, but then I must be able to identify or even
mark populations without killing them first!! The only sexing technique I
know is by dissection!
Please help.
Aman