12 V. E. SHELFORD. 



woods are old with occasional seedlings of gray pine intermixed, 

 we find the larvae of C. lepida displaced by those of C. formosa 

 var. generosa, which reach their dominance among the young 

 pines. 



Coming in on the ridges with the pine are the larvae of C. scutel- 

 lavis. In our horizontal series this species is to be found further 

 from the lake than any others yet mentioned. As new ridges are 

 thrown up outside of a given one and as it becomes older, the 

 differences between the lakeward and the landward exposure 

 quickly disappear. 



Let us turn our attention for a moment to depressions. We 

 have noted that C. hirticollis occupies a station on the white sand 

 of the beach. In addition to occurring occasionally in the wet 

 situations just mentioned, the larvae are found in any of the fresh 

 natural depressions that are deep enough to be continually moist 

 at, or near, the bottom. Such depressions sometimes occur on 

 our lake shore, behind a first line of small dunes. As a depression 

 becomes older and the sand becomes somewhat darkened by the 

 decay of the reed, Juncus balticus, the larvae of C. hirticollis give 

 way to those of C. re panda which occur a little higher up than the 

 former, on the sloping sides of the depressions. As the Juncus 

 becomes thicker and a few other plants come in, the larvae of C. 

 repanda become a little less numerous. We have been able to 

 follow this process in an artificial depression. Finally the vege- 

 tation becomes so dense as to drive out the larvae of C. repanda 

 entirely. They are succeeded by the larvae of C. tranquebarica 

 which occur still higher up the side of the depression. This stage 

 is coincident with the development of young gray pines on the 

 ridges. 



Shrubs of various sorts appear on the depression margins at 

 this stage and gradually increase in numbers. The first are the 

 willows and the shrubby cinquefoils. These are succeeded by 

 the button bush and swamp white oaks which make the depres- 

 sion margin too shaded for the larvae of C. tranquebarica and the 

 tiger beetle succession of the depression margins is at an end. 

 This stage. of the depressions corresponds to the establishment 

 of the black oak, which succeeds the pine, on the ridges. 



Returning to C. scutellaris at this stage, we find it still, in the 



