1958] 
Parsons — Gelastocoris 
105 
duing prey, being somehow injected into or ingested by 
their victims, (2) that the secretion is defensive, serving 
to repel predators, or (3) that the glands function as ex- 
cretory organs. The last theory was proposed by Becker 
(1929), but it was attacked by Rawat (1939) who found 
that carmine injected into the head of Naucoris was not 
taken up by the glands ; the first two theories appear to be 
the most popular. In Gelastocoris it is unlikely that the 
secretion of the cephalic glands could be used for killing 
or paralyzing prey, since the orifice is a good distance from 
the beak. It seems most probable that it has a defensive 
function. 
To the author’s knowledge, cephalic glands have been 
reported in only three Gymnocerata. Macgill (1947) gave a 
brief description of two groups of glandular cells in the 
phytophagous bug Dysdercus (Pyrrhocoridae). These cells 
lie near the stylets and open onto the anterior part of the 
maxillary plate, at the base of the labium, by many small 
pores. Macgill considered their function to be the lubrication 
of the stylets; no histological details were given. Bugnion 
and Popoff (1911) figured maxillary glands in a section 
through the head of Pyrrhocoris (Pyrrhocoridae), but gave 
no histological description and did not mention the position 
of the external orifice. A brief account of maxillary glands 
in Oncopeltus (Lygaeidae) was given by Linder and An- 
derson (1955). It seems therefore that the cephalic glands 
are characteristic of the Cryptocerata but occur in the Gym- 
nocerata. According to China (1955), the shore-dwelling 
families Gelastocoridae and Ochteridae are the most primi- 
tive of the Cryptocerata, having diverged from the ances- 
tral line before it became aquatic. To date, however, the 
relationships between the aquatic and shore-dwelling 
Cryptocerata have been hypothesized mainly on the basis 
of external structural characters. The presence of crypto- 
cerate-like cephalic glands in Gelastocoris offers some evi- 
dence from internal morphology that the Gelastocoridae are 
closely related to the aquatic Cryptocerata. 
It might be proposed, on the basis of China’s evolutionary 
theory, that the position of the orifice in Gelastocoris is the 
primitive condition, while that seen in the aquatic bugs is 
