Studies on Body Fluids of Seven Orthopterans, Their pH, Buffering Capacity, and Effect on Solubility of Fractionated Insecticides1

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Abstract
The normal pH of the regurgitated digestive juices from 6 spp. of grasshoppers, viz. Melanoplus mexicanus, M. bivittatus, M. differentialis, M. packardi, Dissosteira Carolina, and Brachystola magna, was detd. They all fell within the pH range 5.2 to 5.8. Titration curves were obtained on the above digestive juices and from such curves the buffering capacities or B values were determined. All of the juices were poorly buffered at their normal reaction as well as for a range of approx. 1.5 pH units on either side of this value. The normal pHs of the blood sera were also detd. for the above spp. of grasshoppers and they all fell within the range pH 6.8-7.2. Titration curves were also obtained for these fluids and their B values detd. The blood of the spp. of grasshoppers studied was very poorly buffered both at and in the vicinity of its normal pH. The solubilities of fractionated samples of arsenious oxide, Na arsenite, and Na fluosilicate were studied in distilled water and in the digestive juices of the Mormon cricket, Arabrus simplex, and in that of 2 spp. of grasshoppers, B. magna and M. bivittatus. With distilled water, in every case the solubility decreased as the particle size increased. In the digestive juices this same general trend was observed but it was not nearly so pronounced. The solubilities of arsenious oxide and Na fluosilicate were considerably less in the digestive juices than in distilled water. Commercial paris green > 50% and air float paris green > 85% more soluble in the digestive juices of B. magna than in dist. water. This was also the trend with commercial Pb arsenate but to a lesser extent.

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