INTERLOCKING MECHANISMS IN COLEOPTERA. 303 



that all of the variations have been discovered. Some light might 

 be thrown on the relationships of the various families of beetles 

 to one another if more were known about these interlocking 

 devices. 



The authors of this paper wish to acknowledge their indebted- 

 ness to Professor E. L. Mark, of Harvard University, for his 

 helpful criticism of the manuscript of this paper. 



BIBLIOGRAPHY. 

 Breed, R. S. 



:o3 The Changes which Occur in the Muscles of a Beetle, Thymalus niargini- 

 collis Chevr., during Metamorphosis. Bull. Mus. Comp. Zool., Harvard 

 Coll., Vol. XL., pp. 317-382, 7 pis., I fig. 

 Packard, A. S. 



'98 A Text-book of Entomology. New York, xvii -(- 729 pp., 654 figs. 

 Sharp, D. 



'99 Insects. Part II. The Cambridge Natural History, Vol. VI. London, xii 

 + 626 pp., 293 figs. 



Biological Laboratory, 

 Allegheny College, 

 Meadville, Pa. 



