1915] Rait — Differentiation of Cocoons 63 



on the surface (Fig. 1.). Closer examination revealed that 

 these were constructed exactly like the dark, firm ones, but with 

 an additional covering. This sheath was of whitish silk, woven 

 loosely into a webby, semi-transparent mesh; it covered the entire 

 cocoon and fitted over it like a pillow-slip closed all around, and 

 was entirely separate from it and could be slipped off without the 

 slightest adherence. It seemed that it had been first constructed 

 in the cell, and subsequently the firm, heavy shell was filled in 

 quite independently. 



The two forms of cocoons were so distinct, and the two types 

 followed so accurately without deviation, that it could not long 

 be considered merely the result of individual temperament. So 

 the following j^ear about three hundred of the cocoons were re- 

 moved from the cells and sorted according to these two forms, and 

 kept under conditions favorable to the development of the insect. 

 Every one of the dark, smooth cocoons brought forth the yellow- 

 legged Pelopseus (Sceliphron), while the cocoons with the ad- 

 ditional webby covering gave forth without fail the steel-blue 

 wasp, Chalybion. 



In addition, a check experiment was carried on to avoid any 

 error that might possibly arise due to artificial conditions. About 

 one hundred mud nests, comprising several hundred cells, were 

 individually placed in covered jelly glasses; when the insects 

 emerged the species was noted and the remains of the cocoon 

 examined, and in every case we found that the yellow-legged 

 wasps had come from the plain cocoons and the metallic-blue 

 ones from the cocoons with a caul. 



A FLY PRESERVED IN PAPER. 



I recently received from my friend, Mr. Germain Beaulieu of 

 Ottawa, Canada, an interesting example of a fly preserved in a 

 sheet of paper in which it had become evenly embedded during the 

 process of manufacture. It was in the last leaf of Vol. VI of 

 "Les Proverbes Dramatiques," printed in Paris by Lejay, rue St. 

 Jacques au Grand Corneille, in 1773. The thinness of the paper 

 makes it easy to study the venation which indicates the genus 

 Rhyphus, and the color pattern, which is apparently still preserved, 

 suggests R. fenestralis. C. W. Johnson. 



