Bulletin STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES, Chief Vol. XVI. BULLETIN Article VI. A Study of the Catalase Content of Codling Moth Larvae BY C. S. SPOONER PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA. ILLINOIS March, 1927 Article VI. — A Study of the Catalasc Content of Codling Moth Larvae. By C. S. Spooner. At the suggestion of Professor Shelford, a series of experiments was undertaken to test the hypothesis that the enzyme catalase might be a determining factor in the dormant period of codling-moth larvae. The method devised by Professor Burge ('1(5) was used with a few minor modifications in determining the catalase content of the larvae. This method consists in collecting and measuring the oxygen gas liberated from neutral hydrogen-peroxide by the catalase present in the crushed larvae. The most surprising fact discovered in these experiments was the comparatively enormous quantities of oxygen obtained from the catalase in a single larva—over 650 cc. being obtained in some cases. The reaction w'as extremely violent, and the gas bubbled off at a surprising rate. The large quantity of gas necessitated an enlargement of the apparatus, with a consequent loss in accuracy. All tests were run for a period of twenty minutes. The quantity of gas was read every minute for the first ten minutes, then at the end of 15 minutes, and finally at the end of 20 minutes. Although the reaction had not entirely ceased at the end of twenty minutes, it had become so slow as to make the continuation of readings useless. The experimental error, though large, is thought to be practically constant and always in the same direction ; that is, the recorded results are proportionally low for all larvae. Table I gives four typical records obtained during the course of these experiments. Table I. Typical Records of the Tolnme of Oxygen (in cc) Obtained from Codling-Moth Larvae. Time in 444 It will be noticed that approximately two-thirds of the gas is given off in the first ten minutes. At the end of twenty minutes the reaction has slowed down so that very little gas is given off after that time. Table II. Summary of Data on Catalase Content of Codling-Moth Larvae. 445 An examination of Table II shows that there is a very great variation in the catalase content per unit of larval weight. One cause of this variation was undoubtedly the difference in the age of the larvae. Food, conditions of the environment after leaving the apple, and individual variation are other possible causes. It seems reasonable to suppose that there is a gradual increase in catalase content up to the time of pupation. This is not proved by these experiments, but the general results seem to indicate that it is a point well worth further investigation. Experiments are planned for this purpose. While it is always a question what any given larva used in the experiment would have done if left alone, experience with several thou- sands of larvae leads to the belief that the general appearance of an indi- vidual when the pupation time arrives, indicates whether it will pupate or not. The plump, healthy-looking individuals nearly all pupate, while those which appear thin and shrivelled remain dormant and eventually die without pupating. The plump, well-conditioned larvae always gave a high catalase content, r),000 cc per gram or more, while those which appeared dried and shrivelled gave a low catalase content, usually about 3.0U0 cc per gram. In the absence of better criteria by which to tell those larvae which would pupate from those which would remain dormant, it is justifiable to suppose that, if the catalase content increases as the larva advances toward the time for pupation, then the catalase content may be a determining factor or at least a correlated factor in the dormancy. Table III shows the results obtained from nine larvae which had been kept over winter in a cool place and subjected to a flow of dry air. Five of these appeared plump and healthy and gave a high catalase content ( Nos. 1, 4, 5, 8, 9). The other four were shrivelled and gave a low catalase content. A control set, which was kept and allowed to pupate, showed that abotit one-half of the lot would probably have pupated. Table III. Catalase Content of Larvae Kept Over Winter in Cool Dry Air. Weight of larva in gms. Gas obtained in cc. Gas per gm. of larval weight. .036 446 Conclusions. 1. Codling-moth larvae contain large quantities of the enzyme catalase. 2. The quantity of catalase per unit of larval weight varies con- siderably in different individuals. 3. Catalase content is directly correlated with the health and continued life of larvae. 4. Catalase content may be directly correlated with pupation and dormacy. In order to test this conclusion a large series of tests should be made covering each day of larval life from the time the larvae leave the apple until time of pupation. Bibliographical Reference. BURGE, W. E. 1916. Relation between the amount of catalase in the different muscles of the body and the amount of work done by these muscles. Am. Jour. Physiol. 41: 153-161.