OF THE MOUTH PARTS OF CERTAIN INSECTS. 189 



of the galea a series of ridges which, under a high power, look extremely suggestive 

 of the structures found in the labella- of Diptera, especially where, as for instance in 

 Bomhylim, the pseudotrachea are imperfectly developed. These ridges vary much in 

 the species; but are particularly marked in a little Andrena near vicina, if not that 

 species itself Here we sec (PI. Ill, Fig. 3) the entire inner face clothed with a tliin 

 membrane which is crossed by numerous closely set fine chitinous lines! I claim that 

 this structure is the homologue of the pseudoti'acheal structure in the Diptera, and that 

 in the latter order it is in the galea that the development occurs, as it does here in the 

 Hymenoptera. The relative differences in size are not of imi)ortance. As to the 

 l)articular use of this structure in Andrena I have no suggestion to make. 



In the Pi-ocecdings Ent. Soc. Washington, Vol. Ill, Mr. Ashmead figures on 

 PI. Ill, some very suggestive mouth structures of parasitic Hymenoptera, of which 

 that of a Pteromalid is reproduced on PI. Ill, Fig. 18. The centi-al labium with its 

 attached structures is much reduced in size, and the maxilliB, bearing the well-devel- 

 oped palpi, are reduced to a single structure, the galea, resting upon what may be con- 

 sidered the sti[)es. Xow if we bring these two parts of the maxilhe a little more 

 closely together, we have almost the exact structure seen in Bihio (PI. Ill, Fig. 11''). 

 The basal ring, bearing the palpi, corresponds almost exactly to tlie basal ring of 

 I'teromalus except for size, while except that the surmounting galea are two-jointed, 

 the correspondence with the upper portion of the structure is ecj^ually marked, 'llie 

 labium in Bihio is much like that figured in PI. Ill, Fig. 14, for Ilermetia, and in PI. 

 I, Fig. 12, for Eiqmriiiihus. 



I am making no very risky statement when I assert that the selerite to which the 

 maxillary palpi are attached must of necessity be maxillary; and fui'ther, it is ctpialiy 

 safe to say that no maxillary selerite can bear a labial appendage : and certainly not a 

 labial palpus. It would be an absurdity, contrary to all the laws of a natural develop- 

 ment, for a modified labial pal[)us to become attached to the selerite bearing also the 

 maxillary [)alpus ; while if we consider it the two-jointed galea, its position is noi'inal, 

 requires no assumption of change or character, and does not difier in any essential 

 l)oints IVom the gale of the roach (I'l. I IF, Fig. 8). Yet these two joints in Bihio 

 will, with a ridged membrane thrown over them, represent the labellale lip of the 

 Muscid proboscis. That such a ridged meniln-ane is well w itliin the range of galear 

 variability we found in the Andrena near viciwi (PI. Ill, Fig. ;>). 



The structure in Eapaniphus hellus (PI. I, Fig. 12) resembles /'/ero7nalus yet 

 more closely, in that a single ring only surmounts the segment bearing the palpus. In 

 this instance the maxilla is reduced to exactly the same segments seen in the Ilymen- 

 opteron, and logic demands that we recognize them as the same. In this case, how- 



