THE JUMPING PLANT-LICE OR PSYLLIDiE OF THE NEW WORLD. 7 



with the front ocellus far from the front margin of the head, and the 

 genge forming the front part of the head with the antennae attached 

 on their front margin. In Eujphyllura, also, a part of the top of the 

 head is formed by the gense (figs. 34, 36). 



Behind the eyes is another sclerite, the occiput, which is often not 

 easily distinguished from the genae, although the suture between it 

 and the vertex above is always distinct. In Livia this is very large 

 and extensive (figs. 3, 20), and the sutures are distinct. In most of 

 the genera, however, it is less extensive and more closely fused with 

 the genae. The occipital foramen is surrounded by this sclerite. 



The clypeus is a relatively large sclerite and very prominent. It is 

 usually pyriform or cordate in shape, but sometimes more or less 

 conical (Aphdlara calthae, PaurocepJiala ilicis, and Ceropsylla john- 

 sonii) . The large end usually overlaps on the f rons and often covers 

 a large part of the latter, as in PsyUa, Trioza, and many other genera. 

 It is often obscured from view from in front by the genal cones which 

 project downward in front of it. The other end converges rapidly 

 toward the labnim and labium (fig. 15). The suture between the 

 clypeus and labrum is quite distinct (in a good preparation), dividing 

 off a relatively small and short labrum. Stough ('10: pi. 29, fig. 1) 

 has indicated an extra suture in the clypeus, and thus the proper 

 nimiber of sclerites is obtained after omitting the frons and calling 

 it the ligamentary process. The epipharynx is a very small and 

 inconspicuous sclerite. 



Appendages of the head. — The labium in the Psyllidse is very peculiar 

 in being sharply flexed at a point between the f orecoxae and the distal 

 portion extending perpendicularly downward. This distal portion 

 only is movable, the basal part being held rigidly between the fore- 

 coxae. The basal segment is thin, being membranous in appearance 

 but really well chitinized. It is more or less internal, being covered 

 partially by the prostemum. At the beginning of the second seg- 

 ment, or at the tip of the first, the labium makes a sharp turn and 

 passes downward. If the head were in the normal position of a 

 generalized insect, this sharp turn would be perpendicularly upward. 

 The f ureas from the prostemum are large and heavily chitmized. The 

 second labial segment passes down directly in front of this and is 

 apparently supported and strengthened by it. In some species, PsyUa 

 alni americana for instance (fig. 15) it seems to be partially surrounded 

 by the furcae. The labium passes out between the legs of the furcae 

 and immediately behind the f orecoxae, thus appearing to arise from 

 the presternum instead of the head. The distal portion of the second 

 segment and all of the third is outside and forms the visible heaJc or 

 rostrum. The latter is movable and may be exserted and drawTi in 

 more or less, being movable on, or within, the profurcae. 

 6060«>— Bull. 85—14 2 



