Spider mite webbing. Part IV: The effect of acaricides on spinning by the carmine spider mite Tetranychus cinnabarinus (boisduval)

Cyhexatin, dienochlor and four experimental acaricides, U‐25322 (1‐benzoyl‐3‐phenylhydrazine), U‐27415 1‐benzoyl‐3‐(2, 4, 6‐trichlorophenyl)hydrazine, U‐42558 [N¹(4‐chloro‐o‐tolyl) N²‐methyl‐N¹‐(phenylthio)formamidine], and U‐42564 [N²‐methyl‐N¹‐(phenylthio)‐ N¹‐(2, 4‐xylyl)formamidine], at 125 mg litre‐¹, induced spindown by the carmine spider mite, Tetranychus cinnabarinus (Boisduval). Cyhexatin caused the largest number of mites to spin‐down, dienochlor the least. Spinning occurred only during the first 6 h after treatment. Mites spun the same average length of threads in response to all compounds. The pattern of spin‐down was even and similar for all the compounds except dienochlor for which it was sporadic. Acaricide‐induced spin‐down is postulated to be an ‘all‐or‐nothing’ reaction.