Insect Mycetomes

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Abstract
After defining the entomological use of the term mycetome a short general account is given of the various supposedly beneficial relationships between insects and internally harboured micro-organisms and the metabolic balance needed. Not all beneficial micro-organisms are harboured in mycetomes or even in mycetocytes, but the present paper is concerned only with insects having mycetomes. It is shown that there is good evidence for accepting the premise that true micro-organisms are found in insect mycetomes and that the micro-organisms supply the insect host with some useful metabolite (s), Special consideration is given to the genusSitophilus, Here the mycetomal micro-organisms probably supply a useful nutrient that is "essential" only when the diet available to the weevils is inadequate. Whole wheat grain appears to be an adequate diet. Some strains of weevils apparently free of mycetomal micro-organisms are pale in colour, light in weight and particularly susceptible to dietary changes. Weevils reared at temperatures too much above the optimum lose their mycetomal micro-organisms. Although the organisms are pleomorphic there is evidence that their morphology in any one strain of weevil, reared under standard conditions, is constant: and thus it seems the micro-organisms may have taxonomic value in entomology. The possible origin of mycetomes and of the mutualistic associations are discussed and suggestions made about future research.