MERSHON EXPEDITION TO CHARITY ISLANDS. 71 



active at the end of seventy-two hours. Seaialiatichic a innnlxT of 

 -different species, died in fort}- to forty-eisht liours. ( 'hrysonu-hdae Hved 

 in the water twelve to forty-ei^ht hoiu's. Tencbrionifhie. five or six 

 species, lived only fonr to ten hours. Coccinellidae, all the various 

 species experimented with lived forty-eight ho\ns and were active up 

 to that time, l)ut were all dead in seventy-two hoiu's and did not sink 

 to the bottom. C'urculionidae shoAved a rather wide range in their 

 ability to resist the action of water, living in some cases only ten hours, 

 others ranging from ten to seventy-tAVO hours. Cryptorhynchus lapatlu 

 Linn." seemed to be very hardy, as it was in good active condition 

 after l)eing in water for a Aveek. 



From these experiments the writer is convinced that the beetles on 

 the northeast shore did not come from the mainland l)ut from the 

 island itself, and hence we do not have in the drift an ex])lanation of 

 the origin of the beetle fauna of the islands. A few .species may have 

 reached the island in this w&y, but of the great numbers that each year 

 fall into the lake waters along the mainland shores very few would 

 reach the island, as the most of them would be drowned long before they 

 had traversed the distance. Yery few, at least in recent years, would 

 ])e carried by drift wood, as little or none is cast up on the shores The 

 ba}^ is very free of anything of that description, although in the time of 

 extensive lumbering in the Saginaw Bay region great quantities of 

 lumber did come ashore and probably l^rought some of the species that 

 are now breeding on the island. The dung beetles found on the island 

 must have reached the island since the lighthouse was built, as before 

 that time they could not live there. None of the large dung l)eetles 

 w(U'e found on the shore of the islands, although very conunon on the 

 mainland. 



It is probable that most of the species have reached the islands l)y 

 flight, and that the growth of the fauna has been slow and accompanied 

 by an elimination of unfit species. Families that require particular 

 conditions not found on the island are apparently not represented and 

 the species that do not make long flights, such as Cicindelidae, are very 

 poorly represented although the conditions are apparently favorable. 



The isolation of the islands is apparently not great for l)eetles. Little 

 or no variation from the mainland type in color or form can be seen in 

 specimens found. This would be expected from the short distance from 

 the mainland. 



LIST OF SPECIES. 



Cicindelidae. 



1. Cicindela sexguttata Fab. One specimen found on the saiidy 

 path, near the southwest shore, June 16. 



