30 Annals Entomological Society of America [Vol. VIII, 
On account of the close relation existing between the 
Homoptera and the Thysanoptera, a comparison will be made 
between the internal head-structures of Cicada and those of 
thrips. Figure 29 is a lateral view of the entire tentorium 
of Cicada showing the invaginations and the arms. The 
invaginations of the anterior arms of the tentorium (i. a.) 
occur at the ventro-lateral ends of the clypeus while the dorsal 
arms are invaginated (i. d.) just ventrad of the antennae. 
Between these two pairs of invaginations distinct, thin, broad, 
chitinized plates extend which are the anterior arms of the 
tentorium (a. a.). The invaginations of the posterior arms 
(i. p.) are found on the lateral margins of the occipital foramen 
adjacent to the maxillary plates described by Muir and Ker- 
shaw. These invaginations give rise to the broad, plate-like 
posterior arms (p. a.) which nearly surround the occipital 
foramen. A small chitinized rod extends across the occipital 
foramen between the dorsal ends of the posterior arms. This 
rod is the body of the tentorium (b. t.) and from its mesal 
portion two long, slender rods arise which extend cephalad 
(d. a.) and unite with the invaginations of the dorsal arms 
(i. d.). These two rods are the dorsal arms of the tentorium. 
In Cicada the ventral ends of the posterior and anterior arms 
unite on each side (xc.) and between these united arms there 
extends across the meson a distinct plate or bridge (zc.). The 
usual association between the appendages of the head and the 
tentorium among insects may be found in Cicada; that is, the 
invaginations of the posterior arms (i. p.) are near the point 
of attachment of the maxillary, piercing organs with the head- 
capsule; the mandibles are associated with the anterior arms 
but on account of their great length and the excessive develop- 
ment of the clypeus, they are not connected near the invagina- 
tions of the anterior arms (i. e.) but connect with the head- 
capsule slightly laterad of the anterior arms near the invagina- 
tions of the dorsal arms; and the invaginations of the dorsal 
‘arms (i. d.) are adjacent to the antennae. 
As mentioned before, the internal head-skeleton of thrips 
undergoes considerable modification and this is well illustrated 
in the various heads figured. In the nymph of Heliothrips 
(fig 12, 18, 19 and 28) the tentorial structures are nearly all 
present, while in the adult of Cephalothrips (fig. 8 and 33) 
