Studies on the Metamorphosis of the Japanese Beetle (Popillia Japonica Newman) II. Changes in the pH of the Blood1

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Abstract
Bishop (1923a), by means of an electrometric method, studied the pH of the blood of the honey-bee larva and found it to vary from 6.77 to 6.95 with an average of 6.83. In larvae which were spinning, he noted an increased acidity, the pH ranging from 6.60 to 6.65. At the conclusion of spinning, the pH rises to its former value in the larva. He suggested that the increase in acidity may be one of the factors causing autolysis of larval tissues. In another paper, Bishop (1923b) reported the effects of acidity on the rate of autolysis of the fat body of the bee, in vitro. He found that in unbuffered solutions, both larval and pupal fat-body tissue autolyzes readily, but the tissue of the pupa to a greater extent than that of the larva. When the mixtures were buffered, the more acid mixtures autolyzed more completely. He concluded that, in vitro, the differences in rate and extent of autolysis of tissue from different stages are due to differences in the acidity of the autolysate. This suggests that the increase in acidity observed during spinning is favorable to the autolysis of larval tissue. Fink (1925) made colorimetric determinations on the blood of several species of Coleoptera and Lepidoptera, at different stages of metamorphosis, and observed a change from a neutral to an acid reaction (pH 6.8 to 5.9) to take place during the prepupal and early pupal development, and the reverse change to occur as metamorphosis is completed. Taylor and Birnie (1932), using a glass electrode, also demonstrated an increase in the acidity of the bee moth, Galleria mellonella, during metamorphosis. The pH values ranged from 5.53 to 6.68 for the prepupae and pupae, and the pH curve was of the U-type.

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