STRTJCTUEE AND BIOLOGY OF SCHIZONEURA LANIGERA, 667 
Smith (1892) observed the presence of these sclerites in 
H emiptera, and Marlatt I’emarks that prior to this author’s 
work the mandibles and maxillae were supposed to be repre- 
sented by the setm alone. 
Marlatt (189.5, p. 247) states in error that the mandibular 
setae in aphids become intimately united ; it is the posterior 
pair of setae (the maxillae) which fuse, and not the mandibular 
setae. 
Bugnion (191 l,p. 643), who cites Heymons (1896-8), “Die 
Mundtheile der Rhynchota,” 'Entom. Nachr. Jahrg.,’ xxii,No. 
11, p. 173), points out that this author showed that the setae 
in Hemiptera only represent part of the mandibles and 
maxillae, the other portions of these structures being more or 
less fused with the wall of the head. 
I have not observed any chitinous sclerites attached to the 
setm and extending from the wall of the head, except those 
mentioned above as the mandibular and maxillary chitinous 
rods. These are evidently supporting structures for the setae. 
The basal portion of each seta is not in any other way con- 
nected with the wall of the head. The insertion of the pro- 
tractor muscles on the mandibular rods would seem to show 
that these rods are part of the mandibles. 
The proboscis is now generally accepted as being homo- 
logous with the labium of other insects. 
As regards the function of the buccal appendages, the 
proboscis acts as a supporting structure for the setm and is 
not used as a piercing organ. Marlatt (1895) has made 
observations verifying this point. The close fusion of the 
maxillary setae in the proboscis groove forms a fine canal 
along which the plant juices are drawn. 
The relationship of the buccal appendages will be best 
understood from the series of sections through the head and 
anterior part of the body, shown in figs. 6-12, 23-24, 25-31. 
The labrum is the anterior prolongation of the clypeus. It 
tapers towards its free end, and is slightly grooved on its 
posterior or internal face, the chitin of the external face being 
marked with a few minute, transverse ridges. 
