Another reference for the dead bee trap is:
 
Gary, N.E. & Lorenzen, K. 1984. Improved trap to recover dead and abnormal
    honey bees from hives. Environmental Entomology 13: 718-723.
 
This trap should be much more effective than earlier designs. The only
disadvantage of the trap admitted by the authors in the article is its
complex design (slow to assemble, not expensive).