678 LAURA FLORENCE 
structures (Plate LX, 2 and 3) which Enderlein (1904:127) interpreted 
as “mandibles” and Sikora -(1916:16) as ‘‘ dreieckige Skelettstiicke.”’ 
Just anterior to the posterior dorsal margin of each is a groove, and at 
its lateral end articulates a rodlike structure which, according to Enderlein 
(1904:128), is the basal part of the mandibles and articulates anteriorly 
with the lateral wall of the head. Serial sections of the head show this 
basal part passing directly into the chitin of the wall, but show no articu- 
lation of the parts, a condition which has been described also by Sikora 
(1916:13-14). At their central angle these structures are attached to 
the sides of the pharynx by a structureless tissue, but it has not been 
found possible to determine the exact nature of the connection. 
Musculature of the stomodaeum 
During the act of feeding, the stomodaeum is moved forward by pro- 
tractor muscles, and by the forward movement of the buccal plate the 
haustellum is protruded and the buccal teeth are everted (Plate LX, 4). 
There are two pairs of protractor muscles, a dorsal pair originating in 
the anterior wall of the head and having their insertion in the posterior 
arms of the buccal plate, and a ventral pair originating in the posterior 
lateral angles of the ‘‘ mandibles ”’ of Enderlein and having their insertion 
in the ventral surface of the knoblike processes at the posterior end of 
the pumping pharynx (Plate LX, 2). By the contraction of these two 
pairs of muscles the whole pharynx is moved forward. 
There are three pairs of retractor muscles, two dorsal and one ventral. 
The former originate side by side on the dorsal wall of the head, laterad 
of the pharynx and just posterior to the muscles passing from the median 
line of the dorsum to the antennae. Both pairs of dorsal retractor muscles 
are of approximately the same dimension, and pass forward to end, the 
outer pair as long, slender tendons inserted in the lateral walls of the 
pumping pharynx in the margin of its fusion with the posterior arms of 
the buccal plate, and the inner pair, which lie close to the lateral wall of 
the pharynx, as much shorter tendons inserted in the dorsal surfaces of 
the posterior knoblike projections on the lateral walls of the pumping 
pharynx. The tendons of these muscles were recognized as such by 
Meinert (1891-92:P]. I, fig. 3), and represent the “fulturae” of 
Enderlein (1904:127). The ventral retractors originate in the latero- 
ventral wall of the head in the region of the anterior level of the brain. 
