Xiv GLOSSARY. 



Front, or front. The space that lies between the eyes (viewed from in front), 

 limited above and below respectively by the vertex and a line drawn 

 through the roots of the antennae. The demarcation between the vertex 

 and the frons may be sharply defined by a sudden angle in the surface, 

 a difference of colour, or there maybe no line of distinct separation. 

 In liibio, for instance, the vertex and frons are practically united and 

 inseparable owing to the flatness of the head. 



Frontal lunule. A crescent-shaped or oval space immediately above the base 

 of the antennae, between them and the transverse slight depression 

 known as the frontal suture. This lunule is frequently indistinct, 

 probably often quite absent, although its presence is the only technical 

 means, according to Brauer, of determining in the imago state whether 

 a given individual belongs to the CYCLORRIIAPIIA. It is prominent in 

 the MUSCID^E, but indistinct or absent in the other three families of the 

 CYCLORRIIAPIIA, viz., SYRPHID.E, PIPUNCULID.E, and PLATYPEZID.E,* 

 though Verrall thinks it traceable in certain peculiarities in the 

 structure of the head in these three families. 



Frontal suture. An impressed line, or very shallow narrow groove of crescent 

 shape enclosing the frontal triangle or frontal lunule. Theoretically 

 present in all Cyclorrhaphic flies, but inconspicuous or absent in three 

 families out of the five. Skuse calls it the frontal fissure. 



Frontal triangle. The small triangle (with the apex upwards) immediately 

 above the base of the antennae, caused by the divergence of the eyes 

 from one another below their region of contiguity. It therefore can 

 only occur in holoptic or sub-holoptic Diptera. 



Fulvous. Golden yellow. 



Gena The cheeks (q. v.) 



Genitalia. The organs of generation. In the male they are technically known 



as the hypopygiuiii, in the female as the ovipositor. 

 Glabrous. Osten Sacken uses this term to define bare eyes in TIPULID.E. It 



is also used in connection with descriptions of wings, meaning smooth 



and shining. 

 Gona2Wphyses. "Four free rods that arise from the wall of the genital 



chamber, two above and two below the base of the penis, and project 



backward within the chamber " (Snodgrass). 



Halteres. The " poisers " of the older school of authors, and " balanciers" of 

 French writers. The atrophied hinder wings in Diptera, reduced to a 

 narrow short stem with a more or less distinct club at the tip. They 

 are placed behind and below the wing, one on each side of the thorax. 



Hemicephalous. A term used by Dufour and others for those Dipterous larva 

 in which the head is not sufficiently differentiated to include them in 

 the EUCEPHALA, yet sufficiently obvious to withdraw them from the 



ACEPHALA. 



* Technically it should be present in these families also, if Brauer's theory 

 be accepted, and its absence seems to weaken considerably its value as a 

 taxonomic character. 



