OF WASHINGTON, VOLTJ.vlE XVI, 1914 173 



The Hydroscaphinoe agree with the Limnebiinae (represented by 

 Ochthebius pygmceus F., (figs. 10-17) in many important charac- 

 ters. They have the same general shape of the body, downward 

 bent head, broad gula (gu, figs. 6, 17), the same number of ocelli, 

 exactly the same unusual shape of all the mouth-parts (figs. 5, 6, 

 10, 11, 12, 16, 17), the same deeply curved hypostoma (h figs. 6, 

 17), homologous processes on the last abdominal segment (figs. 7, 

 14), and similarly formed legs (figs. 8, 13). But the two larva- 

 types differ in the antennae which are very short in the Hydrosca- 

 phinoe (fig. 5), and rather long in the Limnebiinae (fig. 16). Tho 

 Hydroscaphinae lack the clypeus (fig. 5) which is distinctly devel- 

 oped in the Limnebiinae (fig. 16). The Hydroscaphinge have no 

 spiracles while the Limnebiinse have well developed circular spir- 

 acles (fig. 15) laterally placed on the mesothorax and on the first 

 eight abdominal segments. The Hydroscaphinge have the above 

 described filaments on the prothorax, and the first and the eighth 

 abdominal segments, but no cerci on the ninth. The Limnebiinse, 

 on the other hand, have not these filaments, but have cerci on 

 the ninth abdominal segment (cer, fig. 14). It should be noted, 

 however, that the characters of the last abdominal segments in 

 these two forms seem so similar that it is difficult not to consider 

 them homologous. The true explanation may be that the first 

 abdominal segment in Hydroscapha has become obliterated under 

 the strongly developed thorax and that thus what I have cautiously 

 determined in this larva as the first abdominal segment is really 

 the second and that the filaments described as belonging to the 

 eighth abdominal segment belong to the ninth, and that what has 

 been described as the ninth and tenth abdominal segments is 

 merely the divided tenth segment. The absence of the spiracles 

 in Hydroscapha makes the interpretation very difficult but the 

 arrangement of the spines and sensory punctures makes it evident . 

 that if any segment is absent it must be the first; it is however 

 possible that it is the eighth and ninth segments which have be- 

 come amalgamated. 



It is worth noting that the larvae of the Limnebiinse and the 

 Hydroscaphinae are very similar to the larvae of the small Staphy- 

 linidae of the Tachinus-Tachyporus group. In fact these three 

 forms seem to be more closely related to each other than the small 

 Staphylinids are to the normal Staphylinid type and than the 

 Limnebiinee and the Hydroscaphinae are to the typical Hydro- 

 philidse. 



All figures are camera lucida drawings by the author. 



