rt en Annals Entomological Society of America [Vol. VIII, 
Cephalothrips yucce (fig. 8, 9, 11, 17, 18, and 20).—A line 
extending between the vertex and the mouth-cone on the head 
of a nymph or adult of Cephalothrips has a cephalo-caudal 
position and thus in all its stages the position of the head- 
capsule resembles the position of the head of an homopteron 
(Cicada.). The nymph of Cephalothrips is very different from 
the nymph of Heliothrips. 
The head-capsule of the nymph and adult is smooth and 
non-reticulated. The mouth-cone of the nymph occupies 
about one-half the ventral aspect of the head (fig. 17), while in 
the adult it is reduced to about one-third the ventral aspect 
of the head (fig. 8). This reduction is clearly shown in the 
semi-pupal stage (fig. 20). The dotted line across the head 
indicates approximately the point of attachment of the mouth- 
cone as it would be in an active nymph. This line is dis- 
tinguishable in the early stages of the semi-pupa by a difference 
in the staining quality of the two areas on the ventral aspect 
of the head. With the reduction of the mouth-cone of the 
Tubulifera, striking modifications have resulted in the form 
of the clypeus, the left maxillary sclerite, and the piercing 
organs. The modification and the reduction of these parts 
during metamorphosis are of great value in determining their 
homology. 
Symmetrical, caudal projections (c. a.) are present at the 
ventro-lateral margins of the head-capsule of the nymph and 
adult. The caudal projections of the adult are prominent and 
terminate in distinct acetabula which fit against certain sclerites 
of the prothorax (p.s.). This arrangement permits of a dorso- 
ventral movement of the head. 
The asymmetry of the caudal margin of the front of the 
adult is not prominent and in the nymph no asymmetry can 
be seen. The recurrent angle in the adult is located in a 
position similar to that in Heliothrips. 
An unidentified suture (s.) occurs on the lateral aspect 
of the head-capsule of the adult dorsad of the caudal projec- 
tions. There is also an indication of a suture along the dorso- 
caudal margin of the head. This suture along with the 
thickenings and invaginations on the frontal and genal areas 
of the head will be considered later with the discussion of the 
internal head-skeleton. 
