1914] Tower—Mechanism of the Mouth Parts of the Squash Bug 107 
labium is attached, are fused to the inside of the maxillary lamina 
and to the buccule along the line of union of the lamina with the 
buccule. 
A very delicate chitinous rod (i) which broadens dorsally is 
situated internal to each compound eye. Each of these rods is 
attached to the dorsal surface of the same small knob-like 
projections of the genx below the compound eyes, to which the 
chitinous rod that articulates with the base of the maxillary setz is 
attached, see Pl. 1 f. 7 (p), and extending upward and slightly 
forward is attached just above the eye. These rods apparently 
act as protectors and supports of the eye structures and a few 
muscle fibres from the antennz are attached to them dorsally. 
There are two thick strong struts projecting inward from the 
head capsule, one on either side of the head, located slightly ante- 
rior to and inward from each ocellus. These form the base of 
attachment for most of the antennal muscles. 
The labrum is a very flexible sclerite. It contains numerous 
muscles, tracheze and nerves. The action of its muscular system 
has not been worked out. 
The labium is controlled by two muscles, of these the protractor, 
or extensor, extends down the labium beneath the anterior surface 
and is attached basally to a small process of the tip of the tentorial 
plate to which the labium is attached. The retractor muscle ex- 
tends down the labium posteriorly and basally is fastened to the 
ventral surface of the plate with which the labium articulates. 
BIBLIOGRAPHY. 
1883. Geise, Otto. Die Mundtheile der Rhynchoten, Archiv. f. Naturg., vol’ 
xlix, pp. 315-373, pl. X. 
1885. Wedde, Hermann. Beitriige zur Kenntniss des Rhynchotenriissels, Archiv. 
f. Naturg. (2) li. pp. 113-143, pls. VI and VII. 
1892. Smith, John B. The Structure of the Hemipterous Mouth, Science, vol. 
xix, No. 478, pp. 189, figs. 1-5. 
1896. Marlatt, C. L. The Hemipterous Mouth, Ent. Soc. of Wash. vol. ii, pp. 
241-250, figs. 21-23. 
1911. Muir, I’. and Kershaw, J. C. On the Homologies and Mechanism of the 
Mouthparts of Hemiptera, Psycue, vol. xviii, No. 1, pp. 1, pls. 1-5. 
1911. Bugnion, E. and Popoff, N. Les Piéces Buccales des Hémiptéres (Premiére 
Partie), Arch. Zool. Expér. et Général, 5° Série, vol. vii, pp. 643-674. 
1912. Muir, F. and Kershaw, J. C. The Development of the Mouthparts in the 
Homoptera with Observations on the Embryo of Siphanta, Psycuer, vol. 
xix, No. 3, pp. 77, figs. 1-4. 
1913. Tower, D. G. The External Anatomy of the Squash Bug, Anasa Tristis 
De G., Am. Ent. Soc. Amer., vol. VI, pp. 427-437, pls. LV-LVIII. 
