68 MICHIGAN SURVEY, 1908. 



sand beaches, were collected but once. The butterfly, Pyrameis cardm 

 Linn. (39) flew out of the woods, rested a moment on the gravel, and 

 then visited a dogwood flower. The single wasp (41), AmmopMla sp., 

 was seen flying low over a small area of sand near the water's edge on a 

 gravelly beach. 



Some fossil beaches were observed, rising several meters above the 

 lake. The gravel was then thinly covered with lichens, and in some 

 cases even supported a scanty growth of flowering plants. A beetle, 

 (37) Leptura chrysocoma Kby., was collected on a ro^e in such a place. 



The contents of the drift washed up on the beaches is of some inter- 

 est as indicating a possible way in which new forms might reach the 

 island. Here were found Lvmnaea stagnalis (19) ; a dead butterfly, 

 Avosia plexippiis Linn., (19) ; some dead ladybugs, Anatis IS-punctata 

 Oliv. (21) ; shells (21) ; butterflies (21) ; one snail shell, Polygyra albo- 

 Idbris (Say), badly broken but still containing part of the body (39). 

 The vegetable drift (18, 21) included cones or fruits of jack pi'ne, balsam, 

 arbor vitae, and alder. 



Sand beaches are formed in the same way and under the same condi- 

 tions as the gravel beaches already mentioned, but only where the wave 

 action is much reduced by distance from the lake. The principal ecologi- 

 cal difference between the two lies in the presence of the sand, affording 

 a fairly uniform surface, and a finer substratum in which various species 

 may live protected from predaceous ants and spiders. 



The principal beach studied was at the head of Conglomerate Bay, 

 {Fig. 4), and may be described in some detail. The beach was more than 

 100 meters long, and divided at the middle by a small stream running 

 through it into the bay. One portion was only 2-6 m. wide, and over- 

 hung by alders. There the sand was always moist, and the fauna very 

 scanty. The other portion was 10-20 m. wide, fully exposed to the sun, 

 and sloping very gently back to the usual zone of alders. There was 

 some drift wood scattered about over it. 



A warm sunny open place like this attracts many casual visitors from 

 the neighboring woods. Three species of butterflies were especially char- 

 acteristic. Papilio turnus (No. 29) was the most abundant. Tbey flew 

 back and forth along the beach at a general height of 2-3 meters, occa- 

 sionally flying out over the water and dipping into it now and then. 

 They very seldom alighted on the sand. The red butterflies (No. 29) 

 hovered low over the sand but when they alighted chose grass or low 

 shrubs along the margin. No. 29 includes Pyrameis hunteri Fabr., 

 Pyrameis carckii Linn, and Basilarchia wrthemis Dru. 



The black butterflies were not common (No. 29). They flew rapidly 

 and irregularly over the sand and the edge of the water at a height of 

 1-3 m. and very rarely alighted. Two other casual visitors were ob- 

 served but not caught; a red winged grasshopper which flew over the 

 sand at a height of 2 m., and dragonflies which hovered over the small 

 stream. Both came from, and returned to, the woods. 



Peculiar to the beach were small blue butterflies, Phyciodes tharos 

 Dru. (No. 29), and two or three species of sand-wasps (No. 31), includ,- 

 ing Diodontus n. sp., AmmopMla sp., and Xanthosarus latimaniiK Say, 

 which flew rapidly over the surface at a height of about 1 dm. but very 

 rarely alighted. When dead they were preyed upon by ants. One 



