170 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



inserting the mouthparts in the sternum of the third abdominal 

 segment and lay appressed to the ventron of the host with the 

 head directed caudad (Plate 11, fig. 2). That the parasite was 

 actively feeding was evidenced by the rhythmic pulsations of its 

 body. The parasite larva was 5 mm. long and 2 mm. in diameter, 

 nearly cylindrical and glaborous; the head was pale buff and the 

 body translucent with many floculent bodies visible through the 

 transparent skin. The lateral trachae were very distinctly vis- 

 ible. On the terminal dorsal segment was an irregular shield of 

 rugose lemon yellow skin bearing two short hairs. A more de- 

 tailed description was impossible on account of the danger of 

 injuring the parasite by exposure to light and air. On July 29, 

 six days after finding the larva in the field, the parasite left its 

 second host, which it had entirely consumed except a small 

 amount of tissue in the anterior end and the skin. It spun a 

 silken cocoon (Plate 11, fig. 1) on the surface of the soil in the rear- 

 ing cage. In texture this cocoon was tough and leathery, very 

 much like that of Myzina (Elis) 5-cincta (Fab), with some loose 

 strands of silk thrown irregularly about it. When first spun, this 

 cocoon was a rich reddish brown, but in the course of a couple of 

 days it assumed a light tan color. The cocoon is cylindrical and 

 somewhat truncate at each end, measuring 9 mm. long and 3.5 

 mm. in diameter. On August 30, thirty-three days after spin- 

 ning its cocoon, the adult parasite emerged and was determined 

 by Mr. S. A. Rohwer as Pristocera armifera (Say) <? (Plate II, 

 fig. 3). This insect belongs to the Bethylidae, an aberrant group 

 of vespoids formerly classed with the Proctrotrypoidea. The de- 

 scriptions of the male and female by Ashmead are to be found in 

 Bull. U. S. Nat. Mus. 45, p. 34, 1893. 



The adult emerged by gnawing an irregular circular hole in 

 one end of the cocoon. It did not cut off a little cap, as do many 

 Hymenopterous adults on emerging, but reduced the material 

 from the opening to very fine fragments. It returned to the co- 

 coon whenever exposed to the bright light, evidently for conceal- 

 ment, and is very likely nocturnal in its habits. 



EXPLANATION OF PLATE xi. 



Fig. 1. Pristocera armifera (Say) cocoon and remains of two host larvae. 

 Fig. 2. Limonius agonus (Say) larva with mature larva of Pristocera 

 armifera (Say) in feeding position. 



Fig. 3. Pristocera armifera (Say) adult cf dorsal and lateral aspect. 



