1909.] NATURAL SCIENCES OF PHILADELPHIA. 569 



show an interesting series: Pcecilochroa, which leaves the cocoon 

 attached to the nest and holds it until hatching; Drassus, which cuts 

 loose the cocoon from the nest wall, but which also holds the cocoon 

 continuously until hatching; Prosthesima, which makes a much thinner 

 nest and holds the cocoon within it, but not tenaciously, and occa- 

 sionally places foreign objects on its surface; and Geotrecha, which 

 makes only a very slight nest (bivittata) or no nest at all (pinnata), and 

 which does not guard the cocoon, but regularly garnishes it with foreign 

 matter. The last condition is probably the most modified, for it 

 represents the loss of the maternal instinct. At the end of this series 

 the number of eggs is least. 



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