THE ]\IOU;srT DESERT EEGION 99 



Dytiscus Linnaeus 



D. YERTicALis Sav. (2638). This species had never been seen 

 on the Island until taken in large numbers at the same time 

 and place as that next below. 



D. DAUEicus Gebl. (2645). This species is found in very few 

 numbers in the smaller ponds. On July 30, '35, a man in 

 Tremont reported that his trout were being eaten up by 

 lizards. Upon investigation they proved to be the 'water 

 tigers' of this and (D. verticalis) and the pool was fairly 

 swarming with the adults, they having evidently hatched 

 during the previous week. Upon investigation, this spring 

 which had been made into a pool, had no connection with any 

 other body of water, and was on a hill and therefore the 

 absence of the eels, which are the common enemy of this 

 family, permitted them to multiply in peace. 



D. sp. A 'tiger' in the house Bar Harbor, June. (Dr. Thorn- 

 dike.) 



Achjus Leach 



A. sEMisuLCATUS Aube (2651). Probably the most generally 

 distributed of this family, being in most of the small j)onds 

 from the 1st of July until October. 



Graphoderes Thomson 



G. ciNEREus (Linn.) (2660). One specimen taken station F129. 

 Scarce. 



Gyrixidae. The Whirligig Beetles 

 Taken by netting them on the surface of the water. 



DiNEUTES MacLeay 



D. NiGRioR Robts. (2679). Not common. New Mill Pond, July 



21, '34. 

 D. AMERicANus Say. (2680). Record of capture lost. 

 D. HORNi Robts. (2681). Ice ponds in Manset, June 11 and 



New Mill Pond, Aug. 7. 



