Method for increasing yield of silkworm cocoons employing juvenile and moulting hormones

A method for increasing the yield of silkworm cocoons which comprises administering to silkworm larvae, orally or through the body surface by means of spraying or dipping, an insect juvenile hormonal factor, which prevents silkworm larvae from metamorphosis, in an amount of from 0.01 to 100 .mu.g.per silkworm larva in a period of from 24 to 96 hours after the start of feeding for their final instar, and administering to the silkworm larvae, orally or through the body surface by means of spraying or dipping, an insect moulting hormonal factor, which induces final-instar silkworm larvae to metamorphose into pupae, in an amount of from 0.1 to 50 .mu.g.per silkworm larva in a period of from 110 to 288 hours after the start of feeding for the same instar, wherein

• the insect juvenile hormonal factor is selected from the group consisting of a compound of the formula ##SPC4##
• wherein R.sup.1 and R.sup.2, respectively, represent alkyl of 1 to 4 carbon atoms, m is zero or 1 and n is zero, 1 or 2;
• a compound of the formula ##SPC5##
• wherein R.sup.3, R.sup.4 and R.sup.5, respectively, represent alkyl of 1 to 4 carbon atoms and q is zero or 1;
• and a compound of the formula ##SPC6##
• wherein R.sup.6 and R.sup.7, respectively, represent alkyl of 1 to 4 carbon atoms, R.sup.8 represents chlorine or alkoxy of 1 to 4 carbon atoms, R.sup.9 represents hydrogen, or R.sup.8 and R.sup.9, taken together, represent oxygen, X represents oxygen or sulfur, R.sup.10 represents alkyl of 1 to 4 carbon atoms, nitro, halogen or alkoxycarbonyl of 1 to 5 carbon atoms, R.sup.11 represents hydrogen, or R.sup.10 and R.sup.11, taken together, represent methylenedioxy, and
• the insect moulting hormonal factor is selected from the group consisting of .alpha.-ecdysone, .beta.-ecdysone, inokosterone, cyasterone, ponasterone A and ponasterone B.