64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



palpigers may not be dififerentiated from the rest of the prementum, 

 and are frequently entirely membranous. Frequently there are no 

 glossal or paraglossal lobes visible, as in Osorius (fig. i8B) and 

 Leptochirus (fig. i8 G), but in some forms they appear to have united 

 into a pair of lobes or even a single lobe, as in Lathrbnacuut (fig. i8 C) 

 and Gastrolohimn (fig. i8 H) , whereas in others there are both glossae 

 and paraglossae distinct, as in Baryodina (fig. i8D). In Liparo- 

 cephalus (fig. i8E) there is a united glossa or ligula which is pro- 

 longed into a cyHndrical sclerotized piece projecting cephalad for 

 nearly half the length of the first segment of the palpi. 



Any of these parts may occasionally bear large setae or minute 

 setulae. It must always be borne in mind in examining the labium 

 that the hypopharynx almost invariably is furnished with a pair of 

 lobes bearing combs of setae which project up behind the paraglossae 

 and are likely to be mistaken for them. They are always membranous 

 like the paraglossae, and the distinction between them is sometimes 

 difficult to make. 



The number of segments in the labial palpi is said to vary from 

 one to four. None have been recorded with less than three except 

 from the subfamily Aleocharinae, and the only examples with four 

 are there also. In almost no cases are there definite articulations be- 

 tween the segments of the palpi, each one being united to the next 

 by a relatively wide area of membrane. Frequently also the segments 

 are rather indefinitely sclerotized but usually sufficiently so to prevent 

 any difficulty in counting them. 



No specimens have been studied which have only one segment in 

 the labial palpi. One species has been observed with two-segmented 

 palpi. This is Liparoccphalus (fig. 19 B), in which the basal segment 

 is partially divided into two. It is evidently an intermediate step in the 

 formation of either the three-segmented from the two-segmented 

 condition or the reverse. The closely related genus Dianlota fre- 

 quently shows both the extremes and all the intermediate steps in a 

 single lot of the one species. 



The three-segmented condition of the labial palpi is almost uni- 

 versal throughout the family, but a great deal of variation in form 

 is apparent. As a rule the labial palpus cannot be said to be filiform, 

 though certain segments may be slender in certain species. The basal 

 segment may be longer than either of the others, as in Habroceriis 

 (fig. 19 E) and Stenus (fig. 19 C), or shorter, as in Hypocypfus (fig. 

 19 F) and Osorius (fig. 19 J). It may be rather strongly geniculate 

 as in Stenus (fig. 19 C) and Osorius (fig. 19 J), or may be large and 



