100 
Psyche 
[December 
midline, but diverge from each other posteriorly in the 
region of the subesophageal ganglion. They are bordered 
dorsally by the mandibular lever and the retractor muscles 
of the mandibular and maxillary stylets, and laterally by 
the sides of the head. The fact that these structures con- 
tain copious amounts of a milky secretion, and that their 
lumina open through definite orifices, suggests that they 
are glandular in nature. When the bug is disturbed, large 
quantities of this secretion are emitted from the large ori- 
fices, which are located on the ventral surface of the head 
just anterior to the antennal sockets (Fig. 1). In the fol- 
lowing discussion, the term “orifice” will refer only to the 
hole in the exoskeleton, while the mouth of the gland, lying 
beneath the orifice, will be termed the “glandular opening.” 
The opening mechanism of the gland is controlled by a 
slender muscle, which originates on the tip of the posterior 
wing of the hypopharynx and runs ventral to the gland 
to insert on a flap on the medial side of the glandular open- 
ing (Fig. 4). This flap is sclerotized and elastic; its two 
Explanation of i j l\te 12 
Figures 1-3. Ventral views of the heads of representative Crypto- 
cerata, showing the positions of the orifices of the cephalic glands. The 
eyes are colored solid black. Figure 1. Gelastocoris oculatus oculatus. 
The dotted lines indicate the approximate position of the cephalic glands 
inside the head. 20 X. Figure 2. Notonecta undulata. 10 X. Figure 3. 
Belostoma flumineum. The labrum and labium have been cut off at the 
base of the second labial segment. 13 X. Figures 4 and 5. Views of the 
inner ventral surface of the head of Gelastocoris, showing the opening 
mechanism of the left cephalic gland. The anterior direction is to the 
top, the posterior direction to the bottom, the lateral direction to the 
left, and the medial direction to the right of the diagram. 375 X. Figure 
4. The muscle is relaxed, and the glandular opening is shut off from the 
orifice in the exoskeleton. Figure 5. The muscle is contracted, and the 
glandular opening is pulled over beneath the orifice. 
Abreviations Used in Plate: A — antenna; F — sclerotized flap 
on medial side of glandular opening; G — gula; L — labium; LG 
— - lateral wall of glandular opening; LB — labrum; M — muscle in- 
serting on sclerotized flap; MG — medial wall of glandular opening; MP 
— maxillary plate; O — orifice in exoskeleton of head; OF — occipital 
foramen. 
