PROC. ENT. SOC. WASH., VOL. 23, NO. 1, JAN., 1921 7 



fundamentally the same throughout the Hemiptera. But a 

 satisfactory interpretation of the parts in terms of general insect 

 morphology is quite another matter. Most entomologists have 

 regarded the Hemipteran setae as the homologues of the mandi- 

 bles and maxilla? of biting insects. Suppose we carry out a di- 

 rect comparison between the head of an adult cicada (fig. 6) and 

 the head of a grasshopper (figs. 1, 2 and 3) by transferring the 

 setae of the former to the mutilated head of the locust (fig. 3) 

 and inserting them into the bases of the mandibles (md) and the 

 maxillae (nix]. Do we convert the Orthopteron into a Hemip- 

 teron by such imaginary grafting? By no means, for the first 

 setae would then arise at the sides of the hypopharynx (fig. 3, 

 Hphy], above its membranous connections (a] with the lateral 

 head walls; whereas, in the cicada (fig. 6), all the setae arise from 

 deep pouches behind the wings (a) of the hypopharynx. On 

 the other hand, if we leave the Orthopteran head as it is in 

 figure 3, minus mandibles and with but stumps of maxilla:; 

 (;#), and insert the setae at the point .v between the hypo- 

 pharynx (Hphy) and the base of the labium (Lfr) we transform 

 it, in external appearance, into a veritable Hemipteron. Note, 

 in this case, how the lobe b and its appendage c in the cicada 

 (fig. 6) correspond with the stump of the grasshopper's maxilla 

 (fig. 3, nix]. Now, observing the position of plate A on the 

 cicada head and its relation to the hypopharynx, the question 

 naturally arises, does the sclerite A in any manner represent the 

 Orthopteran mandible? 



Our only safe guide to morphology is comparative embry- 

 ology when we are sure we have all the facts in the case. The 

 first writer on Hemipteran development, Mecznikov (1866), 

 stated that the embryonic mouth appendages of the Homoptera 

 are, in an early stage, the same as those of other insects; but 

 that, at the time the labial appendages are uniting with each 

 other, the mandibular lobes fuse with the side walls of the head 

 and the maxillary lobes are reduced to small spurs. He further 

 describes the setae as independent structures subsequently 

 developed from retort-shaped masses of cells within the head. 

 According to Mecznikov, then, we might suppose that the 

 mandible becomes sclerite A or a part of it, and the maxilla the 

 appendage c, or c and b (fig. 6). The setae would be in this case 

 neither mandibles nor maxilke but new organs developed for 

 the special function of piercing and sucking. 



Later, J. B. Smith (1892) proposed an interpretation some- 

 what similar to this in which he identified sclerite .-/as the man- 

 dible and named it the "mandibular sclerite," while both 

 setae on each side he regarded as parts of the maxilla, but he 

 claimed, furthermore, that the supposed labium (IJ>] is also 

 formed from parts of the maxilla, and that a true labium is 

 lacking. In this he went so far from the beaten path that IK me 



