. Bulletin - United States National Museum. Science. INVESTIGATIONS ON THE MUTILLID WASPS 19 85 cocoons of Bembix pruinosa I obtained one male and three females of the same Mutillid ranging in size from 11 to 15 mm. When a recently emerged female of the latter group was placed with a male of the small series they mated immediately. The specimens taken in copulation in the field had the following length measurements: Female, mm. and male mm. The adults of Microbembex monodonta vary in size from 8 to 14 mm. while those of Bembix pruinosa vary between 16 and 19 mm. The same propor- tiona
. Bulletin - United States National Museum. Science. INVESTIGATIONS ON THE MUTILLID WASPS 19 85 cocoons of Bembix pruinosa I obtained one male and three females of the same Mutillid ranging in size from 11 to 15 mm. When a recently emerged female of the latter group was placed with a male of the small series they mated immediately. The specimens taken in copulation in the field had the following length measurements: Female, mm. and male mm. The adults of Microbembex monodonta vary in size from 8 to 14 mm. while those of Bembix pruinosa vary between 16 and 19 mm. The same propor- tional differences exist in the size of the mature larvae of the two species. The larvae of DasymuUlla bioculata parasitize the cocoons of both the small Microbembex and the large Bembix and entirely consume the Bembecid larvae before they enter the prepupal stage. The specimens of bioculata emerging from the cocoons of the small Microbembex vary in size from to 10 mm., while those which emerge from the large Bembix vary in size from 11 to 15 nun. Inasmuch as tempera- ture, humidity, light, quality of food, and other ecological factors vary uniformly in this sand dune area, while we know that the quantity of food is considerably less in the Micro- bembex cocoons which produce the small bioculata than the amomit of food in the Bembix cocoons which produce large bioculata, it seems justifiable and reasonable to conclude that the quantity of food avail- able to the larvae of Dasymu- tilla bioculata is the factor which determines the size that the adult will be. The quan- tity of food may be either large or small according to the spe- cies of Bembicid which the Mutillid parasitizes. As stated previously, when a curve is plotted representing the frequency and range of the variation in size of a large number of specimens of Dasymutilla bioculata the curve will be found to be of the bimodal type. The first mode will represent the specimens which as larvae were parasites of Microbembex
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