ANNALS 



OF 



The Entomological Society of America 



Volume III JUNE, 1910 Number 2 



A STUDY ON THE STRUCTURE OF THE EGG OF THE 



WALKING-STICK, DIAPHEROMERA FEMORATA SAY; 



AND THE BIOLOGICAL SIGNIFCANCE OF THE 



RESEMBLANCE OF PHASMID EGGS TO SEEDS.* 



Henry H. P. Severin, University of Wisconsin. 

 (With Plate IX.) 



A detailed description of the eggs of the walking-stick is 

 essential because in the systematic work on the Phasmidae, the 

 eggs are said to be a very valuable auxiliary means of identifi- 

 cation, since their form, "fiir die Genera charakteristisch ist." 

 (Brunner von Wattenwylf). Kaup (8) even remarks, "Viel- 

 leicht wird man spater die Arten durch die Eier schneller unter- 

 scheiden lernen als durch die Thiere selbst!" 



Measurements of Eggs: Heymons (6) found with Bacillus 

 rossi that the size of the eggs is not constant. "Es sind mir 

 Eier zugekommen, wahrscheinlich die letzten, welche das Weib- 

 chen abgesetzt hat, die hochstens die Halfte der iiblichen Grosse 

 besassen, trotzdem waren sie aber normal gebaut und es sind aus 

 ihnen ebenfalls Larven ausgeschliipft." In Diapheromera fem- 

 orata a considerable variability in the dimensions of the eggs is 

 also present but the smaller eggs were not necessarily the last 

 ones which the female lays, — they may appear among the first 

 or at any time during the egg-laying. 



The size of the eggs varies between the following dimensions: 



Length 20-29 rnm. 



Depth, from dorsal to ventral surface 11-18 mm. 



Width or thickness from side to side 9-14 mm. 



* Submitted as a part fulfillment of the thesis requirements for the 

 degree of Ph. D. at the University of Wisconsin. 



+ Paper not accessible. Quoted from v. Brunn's (2) paper. . 



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