Author Institution: U. S. Department of Agriculture, Bureau of Entomolog

Davidson, Ralph Howard

Landis, B. J.

The Ohio Journal of Science

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PROTHETELY IN EPILACHNA CORRUPTA MULS.(COLEOP.)1B. J. LANDIS AND R. H. DAVIDSON,U. S. Department of Agriculture, Bureau of EntomologyProthetely in larvae of holometabolous insects has beenreported for single or few individuals, usually in cases of trans-fer from the field to the laboratory, where the unusual develop-ment became apparent. Observers in reporting on theseindividuals believe the change of environment responsible andlist temperature, humidity, and cumulative quantities ofcarbon dioxide as possible causes.FIG. 1. Prepupa of bean beetle showing wing pads.Such abnormal larvae, in which precocious appearance ofstructures is visible (Fig. 1), have been occasionally observedin laboratory rearings and field collections of the Mexicanbean beetle, Epilachna corrupta Muls., at Columbus, Ohio,over a period of three years.Larvae with wing pads have been observed by the writersfrom three separate localities under field conditions. In thesummer of 1933 at Columbus they occurred in field collectionsxThe writers are indebted to Dr. N. F. Howard, Mr. G. V. Johnson, and Mr.P. G. M. West for much of the material.147148 B. J. LANDIS AND R. H. DAVIDSON Vol. XXXIVfrom June throughout the summer and as late as October 3.Samples of from 200 to 400 larvae taken from a 10-foot unitlength of row yielded two prothetelic larvae on two occasions.In August a larva with wing pads was taken at South Point,Ohio, approximately 125 miles southeast of Columbus, and inSeptember a similar individual appeared in a collection fromWilliamstown, W. Va. In February a larva with wing padswas found among larvae reared in a heated laboratory and inearly June another was taken from larvae reared in a screenedFIG. 2. Prothetelic prepupa of bean beetle sloughing the last larval cuticle.outdoor insectary. It is estimated that one larva with wingpads had appeared for each 10,000 larvae handled at Columbusduring 1932 and 1933. Probably 25 individuals have beenobserved in all and in September 1933 five larvae with wingpads were at hand at one time.Wing pads have been observed only in the fourth instarof the bean beetle. This instar consists of a motile larvalphase and an attached quiescent or prepupal phase. Thepads appear as two pairs of soft saclike evaginations of thedorsolateral walls of the mesothoracic and metathoracic seg-ments. These turgid pads are of nearly equal size and shapeand terminate in slightly pointed tips. The mesothoracic padsare covered with irregular fine brown setae not found on theNo. 3 PROTHETELY 149metathoracic pair. In some individuals collected the anteriorpair of pads were dead and appeared as hard black knobs.vSeveral prothetelic larvae in the late fourth instar wereobserved sloughing the last larval cuticle prior to pupation(Fig. 2). The process was not completed and the individualsdied. No cases were observed where larvae with wing padspassed successfully into the true pupal stage.The wide seasonal and environmental ranges under whichthese unusual forms have been observed suggest that some-thing other than environmental factors may be responsible fortheir appearance.Geology of Puerto Rico.The Geology of Puerto Rico is presented in 5 parts plus Conclusions, Biblio-graphy, Glossary, and Index. In Part I the "Geologic Background" is presentedin which the relation to the neighboring islands is set forth. Part II is "GeologicHistory" in which the actual known geology is depicted from the time of thevolcanic core to the present form of the Island. The geologic column showsconsiderable volcanic rocks of upper Cretaceous age or older. Associated withthese are shales and calcareous deposits, both often with much tuff. TheTertiaries are elastics and limestones of both the reef and shell types. TheQuaternary is generally unconsolidated recent material. Part III entitled"Geologic Materials" is not petrography but a geologic discussion of the rocks,their structures, natural resources and the soils. In Part IV the "GeologicPresent" deals with the physiography and the earthquake factors in the Island.Part V presents rather clearly the numerous questions to which answers are notknown as yet relative to the geology of the region.To briefly sum up the author's conclusions: On a shield of very ancient rockthere was much volcanic activity with the regions between the volcanoes inundatedby the sea. Later this volcanic-marine series was folded into mountains withaccompanying intrusions of igneous rock. This mass was eroded to form thecomplex core. On the margins of this core were formed limestones and clasticdeposits as the mass slowly sank. Then came a long series of uplifts so that thelatter history is one of fluvial planation and uplift, the last uplift developing therifts which set off the Island so abruptly. Now we have erosion working on astill unstable, tilted block.To one interested in the Geology of the region this is a gold-mine of informa-tion. It is unfortunate that the author does not include fossil lists which areavailable. We hope that a latter Monograph will include them, to make theSeries complete. This omission does not deduct from the value of the work.The author has spent enough time in the region to be familiar with the broaderaspects of the geology and the details of numerous small areas and has made gooduse of the literature on the subject. Both Dr. Meyerhoff and the University ofPuerto Rico are to be congratulated and we hope this new series of Monographswill all live up to the first one.—WILLARD BERRY.Geology of Puerto Rico, by H. A. Meyerhoff. 306 pp. Univ. of Puerto RicoMonograph No. 1, series B. 1933.

Prothetely in Epilachna Corrupta Muls. (Coleop.)

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Prothetely in Epilachna Corrupta Muls. (Coleop.)

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