Attempts to maintain large cultures of the onion maggot, Hylemya antiqua (Mg.), have led to the development of special glass cages (Perron et al., 1953). Under oar laboratory conditions the lights used to obtain the degree of illumination necessary for acceptable oviposition rates raised the temperature and lowered the humidity excessively within the cage. Reasonable control of these factors was obtained by atomizing cold water into a current of air blown through the cage.