Changes in Distribution of Nitrogen in Blood of Japanese Beetle, Popillia japonica Newman during Growth and Metamorphosis

Abstract

Determinations were made of the concentration of protein and nonprotein N during larval growth and metamorphosis, and of amino, uric acid and urea N in the blood during the postdiapause feeding period and metamorphosis of the Japanese beetle 25[degree]C. Values are expressed as milligram percent. Protein N is 103 in early 2nd-instar larvae. It rises during the 2nd week of this instar to 221. Ecdysis is associated with a loss of 100 mg. %, the value remaining low until the 3rd week of the 3rd instar when it rises to between 300 and 400 where it remains during diapause. The protein N of hibernating larvae is at the diapause level.. It remains constant during the first 2 weeks of the feeding period and then rises to the premetamorphosis level of 600. The transition of larva to prepupa is characterized by the appearance of granules in the blood and an increase in protein N which reaches a level of 1550 at the middle of the pupal stage when the granules are most abundant. Protein N then decreases reaching a level of 390 on the last day of the pupal stage. Adult emergence is associated with an increase to 990. Nonprotein N remains constant between 400 and 500 during the 2nd and early part of the 3rd instar. It rises on the approach of diapause to a high value of 860 where it remains throughout diapause. During the postdiapause feeding period its concentration varies from 500 to 770. It drops suddenly in the prepupa to 330 and increases during the pupal stage to 800 at the time the granules are most abundant and then decreases during the remainder of the pupal stage to 324. Adult emergence is accompanied by an increase to 900. Centrifuging the blood before protein precipitation reduces protein and nonprotein N to their premetamorphic levels. Amino N remains relatively constant throughout the period of feeding and metamorphosis at 200 to 260. Increases in amino N in the insect as a whole during the prepupal and pupal stages are not reflected by any changes in the composition of the blood. Uric acid remains low at 15 mg % during the feeding period and increases suddenly when the insect becomes a prepupa. This increase is associated with the presence of granules which give a very strong uric acid test. Since there is no loss of N during the metamorphosis of the Japanese beetle, the granules may serve to retain uric acid in the blood, its N later being used for histogenesis. Urea N in the blood of feeding larvae is 26.6. It decreases during the prepupal stage to 15, increases at pupation to 51.8, and then decreases to a level of 15 to 20 where it remains during the latter half of the pupal stage.