1913] 



Johannsen ani Crosby — History of Thryptieus Muhlenbergice 



165 



upon which to base our descriptions, we again visited in April of 

 the present year, the spot where the former specimens were found. 

 From the larva? then collected we reared three females and one male 

 May 16-19, 1913. Nothing was learned of the eggs nor the man- 

 ner of oviposition, but judging from the form of the ovipositor 

 of the female it seems likely that the eggs are laid within the stem 

 plant, probably in May, and that the larva remains thus within 

 the stem until the time of pupation in April of the following year. 



Larva (fig. 1). Length, 5| to 6 mm. Peripneustic. Very pale amber yellow, 

 pharyngeal skeleton dark brown. The combined head and thoracic segments 

 somewhat conical in shape, not differentiated. Abdomen with nine illy defined 

 segments, the anterior ones of greatest diameter, the intermediate longer than wide, 

 anal segment with a prominence on the ventral side, each of the others with a ven- 

 tral transverse band of ambulacral setulse, each band consisting of 12 to 15 strong 

 setulse followed by 2 or 3 rows of more minute ones. The pharyngeal skeleton (figs. 

 2 and 3) consists of a transverse saddle-like structure anteriorly to which is a pair 



Fig. 1. Thryptieus muhlenbergice sp. nov. 



1, larva, x 10. 2, pupa, x 12. 3, pharyngeal skeleton, side view, x 60. 4, phar- 

 yngeal skeleton, ventral aspect, x 60. 5, wing of male, x 20. 6, hypopygium, 

 lateral aspect, x 150. 



of 3-toothed mandibles (a), each one with an elongate supporting segment (b) and 

 a small basal piece, and projecting caudad are six more elongate parts. Two of the 

 dorsal pieces (c) are slender and rod-like, their caudal ends thin and wedge-shaped, 

 between these is a thin, subtriangular piece; two of the ventral parts (d) are rod- 

 shaped, slightly enlarged at each end, a little longer than the dorsal pieces; between 

 these is a thin lanceolate piece (e). 



