Inheritance of resistance to hydrocyanic acid fumigation in the California red scale

Factors influencing the results of fumigation of the California red scale

“…In a total of five separate fumigations with a concentration of 0.115 mg HON per liter for 20 minutes, 1,354 of the resistant crawlers survived and settled, whereas only 11 of the nonresistant crawlers survived and settled out of a total of 2,000 or more crawlers to begin with for each strain. This indicates that the same resistance to HON exists in the scale crawler as in the adult insect, as would be expected in a genetically borne characteristic (Dickson, 1941).…”

“…That is, in some groves there may exist practically a pure strain of the nonresistant red scale; in other groves may be found practically a pure strain of the resistant type; whereas in still other groves a mixture of the two strains is found, which is the result of crosses between the resistant and the nonresistant strain. Dickson (1941) demonstrated that the two strains of scale will interbreed, the F 1 females falling about halfway between their parents in susceptibility to HCN fumigation. Table 3 indicates that in almost every case (the two exceptions each differing by only 0.07 per cent) the 45-minuteexposure to HCN is slightly more efficient in killing the nonresistant and the resistant red scale than the 30-minute exposure.…”

What Can We Learn From Community Genetics?

“…They use several recent examples of the evolution of resistance of populations to path-Special Feature ogens to support this dichotomy, but they might as well have turned to some of the earliest examples of population and ecological genetics. Many of these involved strong selection and rapid evolutionary responses in non-equilibrium systems, e.g., cyanide resistance in scale insects (Quayle 1938, Dickson 1940) and industrial melanism (Kettlewell 1973), often in host-pathogen systems, e.g., sickle-cell trait (Allison 1956), myxomatosis (Fenner and Ratcliffe 1965), and wheat rust (Williams 1975). Clearly, anthropogenic changes in the environment can exert strong selection on populations and elicit rapid evolutionary responses that might have important consequences for communities and ecosystems (Palumbi 2001).…”

The Resistance Movement

“…is sex-linked; HCN-resistance ~n the Calirornia Red Scale Has shown t o be sex-linked. (Dickson, 1941; Yust e t al. 1943).…”