Studies on the infection mechanism of Aspergillus disease in silkworm larvae, Bombyx mori

(I) Growth and ill condition of infected larvae

Abstract

By using larvae artificially infected with Aspergillus flavus-oryzae group soon after the first molting, observations were made on the duration of the second and the third instars, the second and the third sleeping periods and on the mortalities during the feeding as well as the sleeping period.
As the results of this experiment it was concluded that the duration of the second instar of infected larvae was only slightly retarded when compared with normal ones and, on the contrary, it was generally prolonged in the third instar. As for the sleeping period, no difference was observed comparing with the check in the second sleeping period, while it was prolonged in the third one.
The sleeping ratio of infected larvae did not decrease when compared with the check save for the cases with high concentration of fungous suspension in the second instar, whereas it decreased to one half of the check in the third instar. The mortality was similar during the second and the third sleeping periods in the infected larvae, which was larger, in both cases, than the check.
Inoculated larvae usually could never sleep or died during the sleep and, even in the rarer cases of surviving the sleep, they perished with the shrinkage of the body length in serious condition, while in light condition they were usually kept alive during the next feeding period followed by the death during the sleeping period. As was mentioned we could with difficulties find any incubation period in this disease. The relative live weight of inoculated larvae to normal ones began to diminish three days after the infection, remained constant during the second sleep and again diminished rapidly from the beginning of the third instar. The diminishing degree in inoculated larvae was more remarkable than in larvae of Muscardine.
Also the amount of diet and feces began to diminish from three days after the infection and tends to become more distinguished in the third instar.