Aseptic rearing of the silkworm (Bombyx mori) larvae with prepared food has been carried out to know their condition of development, mortality and quality of the cocoon in comparison with those in the usual rearing with mulberry leaves. The results are summarized as follows.
Silkworm eggs within 48hrs. of hatching were disinfected, immersing them in 70% ethanol for 20 minutes and subsequently 0.1% HgCl2 or 2-4% formaline for 20 minutes. The eggs were washed throughly with sterilized water or absolute ethanol and then put in sterilized container.
The newly hatched larvae were put and plugged in the previously sterilized test tubes containing prepared food and incubated at 25°C. The sterilization method of the test tubes and diet was as follows: 100gr of diet (regarding its composition, see the text) was mixed in 160ml of water and introduced into the tube, plugged with cotton and autoclaved (1.2kgW/cm2) for 30-40 minutes.
Rearing circumstance through all the stages of aseptical rearing were always under the condition of closed circumstance with high humidity (about 95%) but the silkworm larvae ate and grew well.
The mortality and body weight of the larvae aseptically reared were almost similar to those in the control worms. Cocoon quality, however, was somewhat inferior in the aseptical rearing.
Cocoon weight and its ratio against the weight (cocoon plus pupa) were 0.22-0.33g and 17.5-19.5% respectively in the aseptical rearing. Those in control 20.3-24.0%.
To make the results sure it was required that (1) thus prepared food should be acceptance of their food by the newly hatched worms, (2) only eggs 48 hrs should be used for axenic work. After hatching, were to be on the sterilized food, (3) the larvae should be transfered on fresh food at least once every week. In case of aseptic rearing with prepared food, it is guessed that there is not so bad influence for the growth of silkworm larvae even if they are reared under the above mentioned circumstances during their larvae's period. It is considered that the aseptic rearing is suitable for prepared food rearing and is available for practice in sericulture to obtain aseptic-silkworm (Germfree silkworm).
