Synergistic effect of two stimulants to induce probing in Stomoxys calcitrans (L.).

Abstract

INVESTIGATIONS into the efficacy of mammalian skin secretions and their decomposition products, and of blood as stimulants of the probing response in blood sucking Diptera (other than mosquitoes) have produced confusing and often apparently contradictory results1–6. Hopkins4 used hungry, water-sated Stomoxys calcitrans in tests to determine possible chemical stimulants of probing, and obtained a positive response to conditions of high relative humidity and to ammonia evolved from aqueous solutions. This response to ammonia was observed in conditions of high humidity and did not occur when ammonia was evolved from dry ammonium carbonate. Hopkins, however, states that ammonia evolved from aqueous solution retains its stimulatory effect at low humidities. Measurements of relative humidity or of ammonia concentration were not made, although calculations of ammonia concentrations based on partial pressure data were given.