ナガマドキノコバエの幼虫用人工飼料と頭幅による幼虫の齢数の推定

概要

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An artificial diet was developed for larvae of Neoempheria ferruginea, a mushroom fly affecting the sawdust-based cultivation of shiitake, Lentinula edodes. The diet mainly consisted of shiitake mushrooms, dried yeast, peptone, and sucrose. Eggs were placed on the surface of the diet and reared at 20°C with a 16-hour light/8-hour dark photoperiod. The hatchability, pupation and emergence rates were 64.0, 45.0, and 42.0%, respectively. To determine the larval instars, larvae were reared on the diet at 25°C under the same photoperiod conditions mentioned above. The larvae were then withdrawn from the diet 5–13 days after oviposition and placed in 70% ethanol, whereupon their head capsule widths and body lengths were measured. The frequency distribution of larval head capsules, including hatchlings, consisted of five groups. The extension ratios between each group were 1.51–1.81, which fitted Dyar's rule, which states that the ratio of post-moult to pre-moult size is constant; therefore, N. ferruginea larvae were considered to have 5 instars. The larval body seemed to lengthen as the larval head capsule widened. In addition, larvae 10 mm long or more were considered to be in the 5th instar.