780 



AN INTRODUCTION TO ENTOMOLOGY 



The facial depression. — See antennal fossa. 



The facialia or facial ridges. — -See vibrissal 

 ridges. 



The front.— (a) The true front (Fig. 998, 

 fr.) is the first of the unpaired sclerites be- 

 tween the arms of the epicranial suture. See 

 above pages 37 and 38. This term has been 

 generally applied to this sclerite since it was 

 proposed by Kirby (Kirby and Spence) nearly 

 a century ago. {b) The so-called front of 

 writers on chsetotaxy is that part of the vertex 

 that extends from the base of the antennas to 

 the upper margin of the head (Fie. 999, Fr.). 



The frontalia. — See frontal vitta. 



The frontal orbits. — See genovertical plates. 



The frontal triangle. — In holoptic flies, 

 those in which the eyes are contiguous on the 

 upper side of the head, the triangle between 

 the eyes and the antennae, the apex of which 

 is above, is termed the frontal triangle. Some 

 times this term is applied to a triangle indi- 

 cated by color or a depression in the corre- 

 sponding position in flies with dichoptic eyes. 



The frontal lunule. — See page 775. 



The frontal suture. — See page 776. 



The frontal vitta. The median portion of 

 the so-called front, extending from the base of 

 the antennte to the ocelli (Fig. 999, f. v.). 



The fronto-clypeus. — This term is applied 

 to the combined front and clypeus when the 

 suture between them is obsolete, as is usually 

 the case in Diptera. It is the part bounded 

 above by the arms of the epicranial suture 

 (Fig. 998, a. e. s) and below by the clypeo- 

 labial suture (Fig. 998, c. I. s.). 



The gencB. — (a) The true genas (Fig. 48, G, page 39). The term genae was 

 introduced into entomology nearly a century ago by Kirby (Kirby and Spence) 

 and was applied to the lateral portions of the epicranium, that part on each side of 

 the head lying beneath and behind the eye; and has been generally used by 

 writers on insect morphology in this sense, {b) The so-called genas of writers on 

 ch£Btotaxy are portions of the cephalic aspect of the head, that part on each side 

 which is dorsad of the transverse impression, laterad of the arm of the frontal 

 suture and mesad of the eye (Fig. 999, g). This region is "the sides of the face" 

 of older descriptions and the parafacialia of some later writers. 



The genovertical plates. — The so-called front of writers on chsetotaxy (see 

 above) is usually distinctly divided into three parts, a median, the frontal vitta or 

 frontalia, and two lateral, the genovertical plates or parafrontalia. (Fig. 999, 

 g-P-)- 



The interfrontalia. — Specialized stripes on the middle of the so-called front, 

 formed from the enlarged ocellar triangle. 



The occiput. — The term occiput is applied by writers on the classification of 

 the Diptera to the caudal aspect of the head, this includes the gen« and post- 

 genas described on page 39. 



The ocellar plate or ocellar triangle. — ^A triangle indicated by grooves or de- 

 pressions on which the ocelli are situated. 



The orbits. — That pa^-t of the epicranium on each side immediately contiguous 

 to the compound eye. The orbit is sometimes indicated by structural characters, 

 at other times it is indefinite. 



The parafacials. — The so-called genae of writers on chastotaxy. 



The parafrontals.- — The genovertical plates. 



The peristome. — The region around the mouth. 



(e ps^ gl md 



Fig. 998. — Hypothetical type of 

 head-capsule of Diptera; a. e. 

 s, arms of epicranial suture; a, 

 f, antennal fossa; ant, antenna; 

 a. s, antennal sclerite; c, cly- 

 peus; c. e, compound eye; c. I. 

 s. clypeo-labial suture; /2, f ur- 

 ea; /3, furca; g, galea, ge, gena; 

 gl, glossa; i. a. and i. d, invagi- 

 nations of the tentorium; /, lab- 

 rum; le, labella; m, membrane; 

 md, mandible; mx. pi, maxilla- 

 ry palpus; oc, ocelli; 0. /, oral 

 lobe; pgl, paraglossa; 5. e. s, 

 stem of epicranial suture; v, 

 vertex. (From Peterson.) 



