MORSE: ORTHOPTERA OF NEW ENGLAND. 
217 
or powerful hand-lens their surfaee will be seen to be made up 
of a large number of minute hexagonal areas called facets, each of 
which is the external end of a single eye element or ominatidium 
(plural ommatidia) with a convex surface {lens). Three simple 
eyes {ocelli, singular ocellus) are situated, one in the middle of 
the prominent ridge running down the middle of the face, the 
others on each side of the ridge opposite and very near the middle 
of the front margin of the compound eyes. Below each lateral 
ocellus is a pit {fossa) from which arises a 'feeler' {ante7i7ia). The 
antennae consist of a series of joints or segments varying greatly 
epicruuUm 
Labium 
6 
Fig. 4. — Front view of 
head of Locust. Enlarged. 
(Original.) 
Fig. 5. — Side view of 
head of Locust. Enlarged. 
(Original.) 
Fig. 6. — Ventral view of 
labium of Locust. Enlarged. 
(Original.) 
in number and form in different members of the family but are 
always recognizable by their position and character. They are 
sense organs, believed to be tactile in function in the Orthoptera, 
and perhaps are equipped with other senses as well. 
The smooth, convex top of the head is called the crown of the 
head; its posterior portion the occipitt or hind head, a term which 
is best restricted to the turned-in part surrounding the Locust's 
neck. The part between and in front of the compound eyes is 
the vertex; by some authors the crown is included in the term 
vertex. The vertex often bears a depression {scutellum verticis) 
sometimes marked in the median line by a faint ridge (carina) 
and may be bounded in front by elevated ridges; the tip of the 
vertex where it joins the frontal casta or facial ridge is the fastig- 
