40 Annals Entomological Society of America [Vol. VIII, 
homology of these pieces it is difficult to determine. However, 
on the basis of the maxillae of other insects, one finds that the 
galea is usually segmented while the lacinia is not. In most 
sucking insects the galea is present and the lacinia may be 
wanting. It would seem that the paired piercing organs were 
galea rather than lacinia as Garman has suggested. For 
convenience of description the paired piercing organs will be 
designated as the maxillary setz (mx.). 
Strong evidence is likewise found in the relation existing 
between the paired piercing organs and the tentorium of the 
head. The maxillae in generalized insects are associated with 
the invaginations of the posterior arms of the tentorium and 
this relation was shown to be true with Cicada. On the basis 
of the homology between the tentorium of Cicada and thrips 
it was shown that the thickening about the occipital foramen in 
the nymph of Heliothrips (p. a.) are homologous with~ the 
posterior arms of.Cicada. In the nymph and adult of 
Heliothrips the paired piercing organs are closely associ-° 
ated with the ventral or caudal ends of these thickenings or 
so-called posterior arms. As mentioned before, no invagina- 
tion of the posterior arms of the tentorium could be found in 
this genus of thrips; however, from the close association of 
the paired piercing organs with the posterior arms of the 
tentorium we may conclude that the generalized relation 
between the posterior arms of the tentorium and the maxillae 
holds for thrips as well as for more primitive insects. 
Further evidence is found in the fact that in generalized 
insects the maxillae are always attached to the head-capsule 
caudad of the mandibles. As was pointed out in the dis- 
cussion of the head-capsule of thrips, the mouth-cone has been 
carried around the head until it is now found at the caudo- 
ventral portion of the head. As a result the mouth-parts 
have a cephalo-caudal extension rather than the generalized 
dorso-ventral direction. This rotation of the mouth-parts 
means that the maxillae should connect with the head-capsule 
dorsad of the mandibles. The paired piercing organs of the 
Terebrantia (mx.) are decidedly dorsad to the asymmetrical 
piercing organ (1. md.), and it will be shown later that the 
asymmetrical piercing organ is a mandible. 
