272 HPULUWB. 



The upper plate of each abdominal segment is known as the 

 tergite, the lower one as the sternite, the segments being 

 numbered from the base onwards. 



The genitalia are by some counted as the ninth abdominal seg- 

 ment, but it seems preferable to regard them as appendages. The 

 dorsal and ventral plates of these appendages if fully developed 

 and supplemented by side or pleural plates certainly resemble an 

 abdominal segment, but these are but parts of the genital organs 

 varving in development with the genus and the species. The 

 structure of the genital organs in the male is of the most diverse 

 character, and affords excellent and reliable means of identifying 

 the species. The general plan is the same in all the groups, but 

 the variation in the appendages is very considerable. Normally 

 there is a pair of strong conspicuous ciaspers * (termed by Osten 

 Sacken the forceps) composed of two joints, of which the basal one 

 is large, stout, subcylindrical or conical : the second joint may be 

 single, bifid or trifid ; it may be of the same structure as the basal 

 joint or take the form of a coriaceous or horny hook, elongated or 

 blunt, straight, angled or curved ; in Limnophila two such hooks 

 being present ; in Gonomyia certain foreign species have a trifid 

 arrangement of the second joint. 



When the second joint consists of two pieces they are not of 

 the same consistency, the outer appendage generally being of a 

 more horny nature whilst the inner one is of softer texture. A 

 second pair of inner ciaspers, or some such organs, are often 

 present, though not easily seen in dried specimens, and a dorsal 

 plate extending below the eighth abdominal tergite is, in most 

 cases, fairly obvious in the more highly developed genera. A 

 ventral plate, sometimes large and V-shaped, extends over the 

 sides of the genital organs, sometimes being reduced to a small 

 curved bottom plate, sometimes in the form of an elongated narrow 

 piece (termed by Osten Sacken the style). Side or pleural plates 

 are visible in many genera of TIPULID^E ; in others they are reduced 

 to a minimum or apparently absent, perhaps replaced by the 

 V-shaped sides of the ventral plate when this latter takes this 

 form. They vary somewhat in their position, being most typical 

 when lying one on each side of the genital organs, but they may 

 be exserted upon the posterior rim of the segment or may form a 

 small plate set in that rim. 



The term hypopygium is given to the whole of the male 

 appendages regarded as a single organ ; the term ovipositor to 

 those of the female. Unfortunately some authors have used the 

 term hypopygium to signify the entire apical enlargement of the 

 male abdomen, which is quite incorrect. "The general shape of 

 the hypopygium in the family TIPULID^E is that of a cup, opening 

 posteriorly. The cavity in the cup is the genital chamber. It is 



* The organs can generally be wholly or almost wholly withdrawn within 

 (he genital chamber, and in individual cases may be difficult of inspection. 



