ODYNEIIUS. 157 



This species, like the preceding, has not been described with 

 sufficient precision to be recognized with certainty, until the 

 number of species has been augmented. It appears to be very 

 near to the 0. debilis in the form of its head and abdomen. 



Subgenus ANCISTROCERUS Wesm. 



The first abdominal segment divided by a transverse suture; 

 its superior face (situated behind the suture) not divided by 

 a deep groove. Antennae of the males terminated by a hook. 



This subgenus includes insects of variable forms, in which, 

 although they are very hard to define, we can distinguish four 

 principal types. These are mere divisions of the subgenus. 



A. The second cubital cell of the wing having a distinct radial side. 



a. Form rather depressed, more chubby; the upper face of the 1st 

 abdominal segment transverse. Ancistrocerus. 1 



b. Form rather cylindrical, more slender. 



* The hinder face of the metathorax more or less excavated; the 



border of the excavation rough or rounded. Stenaucistrocerus. 



** The hinder face of the metathorax having a deep round cavity, 



surrounded by a very sharp circular ridge. Ilypancistrocerus. 



B. The second cubital cell of the wing triangular, quite contracted on its radial 

 side, but not petiolate. Ancistroceroides. 



Division ANCISTROCERUS (properly speaking). 



Saussure Et. Vespides, I, Section 1, a, p. 135 ; b, p. 139. — III, Section 



1, p. 216. 



Abdomen quite depressed, sessile ; its first segment truncate 

 anteriorly so as to show two faces, one anterior and one 

 superior; its two faces distinctly separated by the suture; the 

 superior one forming a wide square or a transverse band. This 

 segment short and wide. Thorax flattened above ; disk of the 

 mesonotum offering at its base two longitudinal grooves. 



The insects of this series have their form rather depressed than 

 cylindrical. They are generally rather wide, but are sometimes 

 slender; the thorax is somewhat cubical, although generally 



1 The division Ancistrocerus is also to be distinguished by the fact, that 

 the yellow margin of the first segment is a band, either regular, or widened 

 on the sides, while in the others it is generally either regular or narrowed 

 on the sides. 



