A Preliminary Note on some Nutritional Requirements for Reproduction in Female Aedes aegypti.

In a previous paper, Lea et al. (1955) reported that a high level of egg production resulted if Aedes aegypti females were fed either citrated blood or skimmed milk from a cotton pad. It was necessary to mix honey with the blood or milk as an attractant to induce feeding, and the most satisfactory ratio of honey to blood or milk was found to be 1:9. Best results were obtained if the mixture was heated to about 100° F before being absorbed on a cotton pad for feeding. Because of the excellent results obtained when milk was substituted for the blood-meal, the writers attempted to find other proteinaceous materials which would stimulate oviposition in Aedes. It was subsequently found that a number of proteins, both plant and animal, when mixed with honey and presented to the mosquitoes on cotton pads, would meet the nutritional requirements for egg production. Among the materials which proved to be successful were human serum albumin, human gamma-globulin, hemoglobin, egg albumin, pepsin, lipase, trypsin, proteose-peptone, and the enzymatic hydrolysates of lactalbumin, casein, soybean meal, and yeast. These results are fully reported by Lea et al. (in press). It might also be mentioned here, that skimmed milk, egg albumin, and proteosepeptone were fed to Anopheles quadrimaculatus, and eggs were obtained in all three cases. No further work with this species has been done, however. The success with the various proteins, and particularly with the protein hydrolysates, led to the hope that oviposition might occur if the mosquitoes were fed a mixture of amino acids, and that it might thus be possible to determine the basic nutritional requirements for reproduction in Aedes females. The importance of the amino acid isoleucine had already been established in studies by the writers. A mixture of 5 g. of beef hemoglobin (Difco) made up to 100 ml. with 10 percent honey water, when fed on a cotton pad daily to a group of 200 female Aedes, resulted in the deposition of 16 eggs in 21 days. However, a group of 200 mosquitoes fed the same mixture but with 1.5 g. of DL-isoleucine added, laid over 6,000 eggs in the same period. These results confirmed the work of Greenberg (1951) who fed Aedes aegypti a number of protein materials through a membrane, but could only induce the insects to feed if washed erythrocytes were present in the food preparation. While egg production with a suspension of sheep erythrocytes alone was low, the addition of several proteins raised considerably the number of eggs produced. In testing amino acids, he found that isoleucine, when added to the erythrocyte suspension, also increased egg production, however, the addition of a mixture of 9 other amino acids caused no increase. It is significant to note that Block and Boiling (1951) have reported that both beef and sheep hemoglobins contain relatively low levels of isoleucine as compared to other hemoglobins and proteins in general. Otherwise hemoglobin appears to contain the normal complement of amino acids.