REPORT OF THE STATE ENTOMOLOGIST I907 



251 



formed by the infolding of the thin connective there, that the 

 primitive receptacle for the sperm mass, whatever may have been 

 its nature, found its origin. The posterior part of the sternum of 

 the 3d segment is little affected, and the anterior part of that of 

 the 2d segment forms the well known, usually flat, " anterior 

 lamina." If the sternum of each abdominal segment consisted 

 originally of two parts, sternum and sternellum, anteriorly and pos- 

 teriorly situated, the penis and hamules and their supporting struc- 

 ture may be supposed to have developed upon the sternellum of the 

 2d segment, while the anterior lamina represents the anterior 

 division, the sternum of that segment. 



Figure 18 is a diagrammatic representation of the relations 

 of tl.e appendages to the sterna of the first three abdominal 

 segments (i, 2 and 3). (a) is a general sketch of segment 

 2 with pp.rts of I and 3. Segment 2 is divided into st sternum 



and stl sternellum. This sketch is merely to aid in the location 

 of the complicated parts of the following figures. The second 

 figure {b) shows the relation of the genital structures in the Libel- 

 lulidae. On segment i no very prominent structures are noted. 

 Small pits are to be seen just anterior to segment 2. Such pits are 

 found among the Anisoptera and in the Zygoptera, not only on seg- 

 ment 2 but also on segment 3. On segment 2 we have at t the 

 anterior lamina, at m the anterior portion of the framework which 

 supports the sheath of the penis in Anisoptera and the penis 

 itself in Zygoptera. This part of the framework is firmly at- 

 tached to and apparently developed from the under side of the 

 anterior lamina, s is the sheath of the penis resting on the 

 framework below. /? is one of tlie single pair of hamules 

 here developed, attached anteriorly to the framework in, posteriorly 

 to the ends of the U-bar s. Between and joining these ends of s 

 there is only a line of chitin n here. This latter is much better de- 



