1916] The Sleep of Insects 



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far enough along to furnish her good shelter for the night, and 

 so on she always plans and executes her day's work so that'each 

 evening she has her lodging-place ready for the night. 



They also noted that the male Philanthus pimctatus, which 

 is without a sting and does not assist in nest building, excavates 

 for himself holes to shelter him for the night, covers the opening 

 with loose soil, and returns to the same abode for several nights. 

 They also mention Pompilus scelestus hanging to a leaf of a 

 plant four inches from her burrow and there falling asleep until 

 after eight the next morning, and the wonderful industry of 

 Crahro stirpicola working at nest-building for forty-two consec- 

 utive hours with only a ten minute interruption. 



Hartman finds that a day's work of Odvnerus dorsalis 

 consists of storing a cell, closing it and building another to be 

 used as a sleeping apartment for the night. 



Fabre records finding on a mountain some hundreds of 

 Ammophila hirsuta assembled under the shelter of a stone. He 

 has speculated much in attempting to account for this gre- 

 garious condition of solitary wasps, but in view of the fact that 

 we have recorded similar phenomena in the sleep of Ammophila 

 pictipennis, Chalybion cceruleum and Elis 5-cincta, we cannot 

 interpret his observations other than that the wasps had 

 come together for the purpose of sleep. 



These mentions will indicate that the subject is pregnant 

 with possibiHties from an ecological point of view, and probably 

 more so from a physiological view-point. The sleep of an 

 organism signifies more than a mere pause in its activity while 

 darkness covers it; while we have not in the present paper 

 touched upon the physiological phenomena of their sleep, we 

 have found many interesting associations of this with the other 

 activities of the insects. For instance, it is of marked biological 

 interest that a few species certainly seem to choose protectively 

 colored situations, and others select sites which are in various 

 ways protective; th^it some which are soHtary by day are gre- 

 garious at night, that some insects sleep with all the regularity 

 of a theoretical modern infant, while others of a more unsyste- 

 matic life snatch a wink when they can. We do not know 

 whether the anemotropism evident in the behavior of some 

 insects is a physiological or psychological phenomenon, or merely 

 mechanical in its origin. 



