PYGOFER OP THE TETTIGIDJE. 163 



more intricate in Deltocephalus, and in the otherwise 

 less differentiated Typhlocybid*. 



The division of the pygofer in the Tettigidae by a 

 diaphragm or wall is not often to be seen ; yet the 

 Cauda is in many species isolated from the other parts 

 by an annular wall. Possibly when the cauda is large, 

 it may form a kind of operculum to conceal, as in 

 Pentatoma, the delicate parts below it, but the pygofer 

 is not retractile to any extent. 



The power of squirting out liquid excrementitious 

 matter may be easily seen in Tettigonia viridis ; when 

 the sprinkling of minute drops during a hot day 

 may be likened to the showers of honey-dew made by 

 Aphides. 



I have never seen ants in attendance on the Tetti- 

 gidae, but they have been reported by some observers 

 as " milking " species of foreign Membracidae. 



The genitalia of Lihimiia straminea and Deltocephalus 

 distinguendus are drawn on Plate E to compare with the 

 genitalia of Poecilochroa and Fiezostermim, and to suggest 

 homologous parts. Although these examples only are 

 taken, a comparison may be continued through other 

 species of Tettigidae ; but we have no reason to expect 

 any exact resemblances between Heteropterous and 

 Homopterous insects. Divergence of form probably will 

 be more accentuated in insects collected from areas 

 widely separated. Nevertheless, for convenience, use 

 has been made of Dr. D. Sharp's illustrations of foreign 

 Heteropterous Homoptera for collation with British 

 forms. For the use of figures 9 and 11, I here tender 

 to Dr. Sharp my obligation. 



At the time of issue of the first parts of this Mono- 

 graph, I had not the advantage of his memoir for 

 consultation. On Plate E, a diagrammatic figure will 

 be found, which may shadow forth some of those parts 

 which appear to be homologous, or at any rate similar ; 

 and the lettering will indicate the terms which T now 

 use for separate parts of the genitalia of Tettigidae. 



m2 



