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time. The "Unit" is the most homogeneous grouping obtainable, given the inci- 

 dence aud characteristics of the disease; once the insects have been placed In 

 the unit, they are handled as an entity and are separated from all other such 

 units to reduce the danger of cross contamination. The unit used to raise a 

 disease-free colony from weevils infected with the mlcrosporidian was the 

 "Family Unit" because the disease was transmitted by transovum passage; 

 selected units were reared through the F, generation, and units containing 

 no disease through adults of the F2 generation were considered disease free. 

 The unit used with weevils infected with M. grandis was again the Family Unit, 

 but these larger groups were then divided into subunits and given the less 

 strenuous treatment of 10-day quarantine. Tlie system produced larger numbers 

 of healthy insects more quickly than selection of progeny from single pairs of 

 weevils. It had the disadvantage that it was more susceptible to failure 

 because of its design, although disease elimination was successful in the test. 



595. . 1967. Development of the bait principle for boll-weevil control. 



II. Field-cage tests with a feeding stimulant and the protozoan Mattesia 



grandis . J. Invertebr. Pathol. 9: 70-77. 

 A formulation containing spores of the protozoan Mattesia grandis and a feeding 

 stfenuiant- made from cottonseed oil and a water extract of cotton squares plus 

 carrier materials and a marking dye was tested against a population of the boll 

 weevil, Anthonomus grandis , on cotton in 1/16-acre field cages. Effectiveness 

 of the formulation was judged by the percentage of marked weevils and the in- 

 cidence of disease among adults collected at the end of the test. Twenty to 30% 

 of the treated population was marked during the main fruiting period, which is 

 also the period of rapid development of the boll-weevil population, and 50% to 

 60% during the latter part of the test when the plants were maturing and fewer 

 weevils were developing because of cooler temperatures. At the end of the test, 

 55% of the weevils were diseased. The diseased population produced about half 



