STUDIES OF VARIATION IN INSECTS 287 



Class E: 201 individuals with both spots of abdominal seg- 

 ment 2 attached by a broad stem, but the ends, /. e., spots are 

 buttoned, /. e., are slightly broader than the stem (fig. 54, ^) ; 

 all these individuals have both spots of abdominal segment 5 

 attached. Subclass i : 89 (of Class E) have the face spot free 

 and subcircular (fig. 55, A). Subclass 2 : 28 (of Class E) have 

 the face spot elongated and nearly attached. Subclass 3 : 78 (of 

 Class E) have the face spot narrowly attached (fig. 55, B). 

 Subclass 4 : 7 (of Class E) have the face spot broadly attached 



(fig- 55, C). 



Class F: 154 individuals with both spots of segment 2 with 

 their attaching stems reduced to mere short broad bars tending 

 to be wider at base (attachment) than at free end (fig. 54, F^) ; 

 all these individuals have both spots of segment 5 attached. 

 Subclass I : 69 (of Class F) have the face spot free and sub- 

 circular (fig. 55, yl). Subclass 2 : 12 (of Class F) have the face 

 spot elongated and nearly attached. Subclass 3 : 60 (of Class 

 F) have the face spot narrowly attached (fig. 55, B). Subclass 

 4 : 10 (of Class F) have the face spot broadly attached (fig. 

 55, C). 



From an inspection of the above there actually seems to be 

 an indicated tendency for the spot in the face to be free when 

 the abdominal spots are free, and for this spot to be attached or 

 fused with the transverse bar above it when the abdominal spots 

 are fused with their corresponding transverse bars. But this is 

 not at all emphasized, being indeed plainly obvious in the case 

 of Class A when compared with any other class, but not when 

 any two of these other classes are compared with each other. 



Variations in the Prothoracic Pattern of Tettigonia sp. (Leaf 

 Hopper). — The Typhlocybinae, leaf hoppers, are small, usually 

 greenish, insects of the family Jassid^, order Hemiptera, com- 

 mon in pastures, vineyards, etc., where they feed on the sap of 

 the green leaves of the growing plants. They occur sometimes 

 in countless numbers, and may do much damage. A lot of 

 221 individuals of Tettigonia sp. collected on one day on the 

 campus of Stanford University was examined and classified by 

 us on the basis of the variations in the number and disposition 

 of the members of a series of small black spots lying just behind 



