82 Annals Entomological Society of America [Vol. XIV, 
Mecoptera and with the Neuropteron shown in Fig. 86, it is thus a 
very simple matter to determine the interpretation of the parts of the 
labium of the Diptera, and if Peterson and Wesche had only used these 
forms instead of trying to compare the Diptera directly with the 
Orthoptera, etc., they would have had no difficulty in determining the 
homologies of the Dipteron structures, so far as the principal features of 
the mouthparts are concerned. I must admit, however, that the 
interpretation of the slender lobes between the terminal segments of 
the labial palpi labeled ‘‘Ip”’ in Fig. 83, has given some trouble. They 
may possibly represent the paraglosse (“‘pg’’ of Fig. 77), for example) 
ot other insects, although I am more inclined to regard them as merely 
lobe-like outgrowths of the segments of the palpi. 
The interpretation of the parts of the labium of the hemipterous 
insects has proven to be a rather difficult problem, largely due to the 
fact that I have not as yet been able to make a thorough study of the 
mouthparts of the Psocidz (which are closely related to the hemipterous 
insects) due to lack of proper material. From what is known.of the 
tendencies for the parts to unite in the Mecoptera discussed above, 
however, I think we are justified in assuming that the sclerites labeled 
“Ip” in Fig. 75 (of a species of Cicada) represent the more or less closely 
united labial palpi, while the structures labeled ‘‘pgr” in Fig. 75, very 
probably represent the palpigers “‘pgr’”’ of Figs. 82, 86, 83, etc., and the 
plate ‘“‘mn”’ of Fig. 75 is therefore largely composed of the mentum; 
the other basal structures of the underlip region are probably included in 
the more membranous region behind the mentum ‘‘mn.’’ When we 
turn to the true Hemiptera (Heteroptera), however, the parts have 
become so modified that it is very difficult to determine their homologies 
in many instances. Dr. Parshley has called my attention to the fact 
that hemipterists frequently interpret the structures labeled “‘ap”’ in 
Fig. 76, as the ‘“‘labial palpi” in the belostomatids; but Heymons does 
not consider that the structures in question are the true labial palpi, 
from his embryological studies. I am more inclined to regard the 
appendages ‘‘ap”’ of Fig. 76, as lateral lobes of the region “‘pgr,’’ which 
have become demarked by the formation of a-secondary suture; and the 
appendages ‘‘ap”’ therefore have nothing to do with the true labial 
palpi, which probably enter into the composition of the sclerite labeled 
“Ip?” in Fig. 76. The structures labeled “pgr” and ‘‘mn”’ in Fig. 76, 
are possibly the palpigers and mentum, ‘“‘pgr”’ and “‘mn,”’ of the Cicada 
shown in Fig. 75. 
I would call attention to the fact that in all of the coleopterous 
larvee which I have examined, the labial palpi, when well developed, 
are made up of not more than two segments, while in all of the neurop- 
terous larvee which might be mistaken for coleopterous larve have at 
least three segments in the labial palpi. This distinction may be of value 
in distinguishing between the two types of larvee, since it is very difficult 
to find any characters for differentiating between the two groups of 
insects, and any distinguishing feature which “holds good”’ in the 
majority of cases, should be of considerable interest on this account. 
