Studies on the development of a chemically defined diet for the two-spotted spider mite (tetranychus telarius L.)

Abstract

An attempt to culture the plant-feeding mite, Tetranychus telarius L. on a chemically defined diet is discussed in this thesis. The development of a suitable rearing technique was one of the important problems. Several methods were tested and only two were proved to be satisfactory. The methods adopted in subsequent experiments were: 1. Introduction of the mites onto a thin collodion membrane supported by a pith disc. 2. Introduction of the mites onto a very thin plastic membrane sprayed on a pith disc. The former was obtained from a solution of flexible collodion liquid (U.S.P.) in amyl acetate which was allowed to evaporate on a layer of lukewarm sterile distilled water. The latter was obtained from a crystal-clear liquid spray in a pressurized can. Pith discs were arranged in rows stuck on a piece of paper towel and sprayed several strokes with the liquid plastic from a distance. Both methods were satisfactory but the latter seemed to have more advantages. The diets developed and tested in subsequent experiments were in liquid form. They consisted of 18 dietarily essential amino acids, sucrose, salt mixture #2 (U.S.P.), 10 important B vitamins, ascorbic acid, cholesterol, linoleic and linolenic acids. The 18 amino acids were: alanine, arginine, aspartic acid, cysteine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenyl- alanine, proline, serine, threonine, tryptophane, tyrosine, valine: The amino acids-carbohydrates ratio was varied from 3:1 to 1:3. Better results were obtained with the higher carbohydrate ratio. Diets that gave best results contained an amino acids-carbohydrates ratio of 2:3; sucrose 2 grams; 50 mg. of salt mixture; 50 mg. of cholesterol; 33.4 mg. linoleic acid; 10.0 mg. of linolenic acid and 203.21 mg. of vitamins. All these were dissolved in 100 ml. of water.