46 Annals Entomological Society of America [Vol. VIII, 
suture is located here. Without any question the mandible 
is hollow, as heretofore explained. The following evidence goes 
to show that the asymmetrical piercing organs of the Tere- 
brantia are mandibular in origin. 
In the first place, as Garman has already mentioned, the 
structure, position, and point of connection of the asym- 
metrical piercing organ with the head-capsule are strong 
mandibular characteristics. It has already been pointed out 
that the invaginations for the tentorial arms on the front of 
thrips are homologous with the invaginations of the tentorial 
arms on the cephalic aspect of the head of Cicada. The in- 
vaginations of the anterior arms of the tentorium on the caudal 
margin of the front (i. a.) are adjacent to the point of connection 
of the left and right asymmetrical organs (1. md. and r. md.). 
This relation shows that the asymmetrical piercing organs of 
the Terebrantia are undoubtedly mandibles since in generalized 
insects mandibles are usually associated with the invaginations 
of the anterior arms of the tentorium. ; 
Furthermore, mandibles in generalized insects are always 
connected with the head-capsule cephalad of the maxilla. In 
the nymph of Helothrips the asymmetrical piercing organs 
are connected cephalad of the maxillary sete but in the adult 
on account of the change of position of the mouth-cone these 
connections are ventrad of the maxillary sete. This relation 
in the Terebrantia shows clearly that the asymmetrical pierc- 
ing organs are mandibular in origin. 
Karl Jordan interprets the left, asymmetrical piercing organ 
(1. md.) as a modified epipharynx. He bases his conclusion 
upon embryological studies. The one embryo figured shows 
the asymmetrical organ as the upper portion of the anterior 
end of the alimentary canal. The base of the so-called epi- 
pharynx is also connected with the head-capsule. He con- 
cludes from this figure that when the adult stage is reached the 
epipharynx loses all connection with the alimentary canal and 
becomes more firmly attached to the head-capsule. The 
above hypothesis in regard to the behavior of the epipharynx 
is contrary to the relations of these parts in other insects. 
Jordan likewise failed to account for the right, rudimentary 
piece (r. md.). On the whole Jordan’s interpretation is very 
unsatisfactory, for it does not explain numerous relations here 
pointed out. 
