1883.] . in the Head of Winged Insects. 1137 
læ arise respectively from the three succeeding segments. The 
figures by Kowalevsky and Bobretsky and by other observers, as 
well as those of the earliest stages of Diplax, Pulex and Atte- 
labus which we have published, show that the cephalic segments 
are first indicated, and that subsequently those appendages bud 
out from the under side at a point situated on each side of the 
sternal or median line of the body. It appears that the append- 
ages arise between the sternal and pleural portions of the seg- 
ment. 
There, however, remains a portion of the head in front of the 
procephalic or antennal lobes which afterwards becomes the clyp- 
eus and labrum or upper lip. Do these parts belong to the an- 
tennal segment, or are they rudimentary portions of a segment 
situated in front of our first segment? This lobe or outgrowth 
is evidently a single unpaired lobe which grows out in front of 
the antennal lobes, and is seen to form the front or upper wall of 
the mouth. We regard it as the tergal portion of the antennal 
Segment, and the procephalic lobes as probably forming the pleu- 
ral portion of the segment. The procephalic lobes, then, bearing 
the antennz below, and higher up on the sides the eyes and 
ocelli, become the epicranium of the larval and adult insect. It 
follows, therefore, that the head of larval and adult insects is made 
up mostly of the first or antennal segment, and that the epicran- 
ium is the pleural portion of this segment, while the clypeus and 
its offshoot, the labrum, is the dorsal or tergal portion of this 
segment. 
The only other portion of the head of certain adult insects 
which remains to be accounted for is the so-called “ occiput.” 
This forms the base of the head of Corydalus, a Neuropterous 
insect, which, however, is more distinct in the larva. In most 
other insects the occiput is either obsolete or soldered to the 
hind part of the epicranium. We have traced the history of this 
Piece (sclerite) in Diplax, a dragon fly, and have found that. it 
“Presents the tergal portion of the fourth or labial segment. In 
our memoir on the development of this dragon fly, Pl. 2, Fig. 9 
the head of the embryo is seen to be divided into two regions, 
the anterior, formed of the first three segments, and the posterior, 
formed of the fourth or labial segment. This postoral <_< 
at first appears to be one of the thoracic segments, but is after 
added to the head. A. Brandt’s figure of Calopteryx virgo, Pl. u, 
