J. H. MERRILL 113 



last segment is nearly twice as long as the preceding segment 

 and narrows rather suddenly towards the tip. 



Thorax 



The prothorax consists of four visible plates; the notum, two 

 episterna, and a sternum. Each episternum (Eps.i) at its an- 

 terior end, articulates with the head by a hooked process which 

 is the remains of the cervical sclerite. The episterna are sepa- 

 rated ventrally by a median longitudinal suture. At the point 

 of articulation with the head, each is quite slender, Imt posteriorly 

 it enlarges and flattens out into a lobe which passes downward 

 and backward below the pronotum and articulates at its posterior 

 end with the procoxa (Cx.i) of an anterior leg. As in most 

 Hymenoptera, the episternum constitutes the greater part of 

 the pleural portion of the prothorax, the epimeron being reduced 

 to a strip so narrow that it is almost negligible, on the posterior 

 border of the episternum and is hidden under the pronotum. 



The pronotum (N.i) is very broad laterally, its anterior face, 

 being narrowed, forms a connection between the lateral plates. 

 The sides are highly polished. The pronotum reaches the base 

 of the tegulae (Tg.) and is produced downward to the episternum, 

 coxae and sternum ventrally. The pronotal lobe (Pnl.) is dis- 

 tinct, though small, forming a peritremal sclerite overlapping 

 the first thoracic spiracle (Tsp.). The sternum is overlapped 

 and largely concealed by the approximated lobes of the episterna. 



In the mesonotum, the prescutum, scutum and scutellum are 

 plainly distinguishable. The postscutellum is small and for 

 the most part is a phragma or internal process. 



Near the upper, posterior corner of the pronotum, on each 

 side and just below the anterior end of the attachment of the 

 fore wing to the body is the first thoracic spiracle (Tsp.). 



The prescutum (Psc.2) is a triangular shaped plate, above the 

 pronotum and separated from the scutum by two sutures which 

 posteriorly converge and become transformed into flattened 

 grooves. The front portion of the prescutum is nearty vertical 

 and forms almost a right angle with its hinder portion, when 

 viewed from the side. 



Medially, the scutum (Set. 2) extends to the raised median 

 portion of the scutellum. Posteriorly the scutum is sunken 



TKANS. AM. ENl, SOC, XLI. 



