OF WASHINGTON. 209 



The position of the antennae should always be mentioned, as I 

 have only illustrated two forms of insertion of these important 

 organs. Sometimes they are placed far above the middle of the 

 face, on the frons, or much below the middle of the face, on a 

 line with the base of the eyes. 



In figs. 8 and 9 I represent two remarkable shaped heads 

 representing a male and female fig-insect belonging to the 

 Agaonidas or Blastophagidae. 



All females in this group have a more or less oblong head, 

 which is grooved above, with a small curved tubercle at base, and 

 with peculiar saw-like appendages to the mandibles as shown in 

 fig. 8. 



Fig. 9 represents a male. The males are always apterous, 

 with slender, weak, or aborted middle legs and stout, strong, 

 much swollen front and hind legs ; the abdomen is long and 

 tubular, being curved under the thorax. 



These remarkable insects live entirely on various fig-trees and 

 are essential to their pollenization. 



Other important characters connected with the head are the 

 mouth-parts, the mandibles, palpi, etc. 



The Swedish entomologist, C. G. Thomson, seems to have 

 been the first to make extensive use of the mandibles in classify 

 ing the Chalcididae. 



After a careful study of them, I agree with him in regard 

 to their value as aids in classification, although neither in this 

 country nor abroad has their value been fully appreciated. 



Figs. 10 and n represent the typical forms found in the 

 Eucharince, a group of the Chalcididae parasitic on ants.- 



These are long, sickle-shaped, with one or two teeth on the 

 inner margin, near the middle. 



Figs. 12 and 13 represent the two types found in the Perilam- 

 pincz, and figs. 14 and 15 represent two inquilinous or parasitic fig- 

 insects, Sycorectes. 



Figs. 1 6 to 22 also represent different types in the Chalcididae. 

 You will observe that they have four, three, and two teeth respec 

 tively ; also that the shape and character of the teeth differ ma 

 terially in the several forms shown. 



In fig. 1 6 the outer tooth is the largest, the three following 



