Odorous secretion of normal and mutant Tribolium confusum.

An autosomal recessive mutant characterized by "melanotic stink glands" has been found in the tene-brionid flour beetle, Tribolium confusum. The contents of the reservoirs of both pairs of odoriferous glands become modified in two ways as the beetles age. (i) The quinones (2-ethyl- and 2-methyl-1,4-benzoquinone) present in the secretion are reduced to 1/20 of that normally found in the wild type. (ii) The contents may be modified into a high-molecular-weight polymeric substance, which becomes visible through the exoskeleton and, upon dissection, appears as a black solid lump. The medium in densely populated cultures of the mutant becomes moldy while that containing normal beetles remains particulate. This difference suggests that one of the functions of the secretions of the odoriferous glands is to prevent the growth of fungi or bacteria in the nutrient flour.