94 UNIVERSITY OF COLORADO STUDIES 



Clistogastra the first abdominal segment is transferred to the thorax and forms part of 

 the second division of the body. The second segment is connected with the first very 

 narrowly along the median, longitudinal axis.) (2) Abdomen composed of ten tergites 

 and ten sternites, in all species known from the county, and in all groups except the 

 Oryssoidea. (In the Clistogastra there are usually not more than eight tergites, although 

 in some Chalcids there are nine.) 



Larvae. — Thoracic and at least one pair of abdominal feet present. The larvae of 

 sawflies, in habits and habitus, resemble more closely those of Lepidoptera than they do 

 those of the Clistogastra. Chalastogastra larvae may always be separated from Lepidop- 

 terous larvae by the simple ocelli. (In the Lepidoptera the ocelli are multiple.) 



There are other characters which separate most Chalastogastra from the Clistogastra, 

 but these do not all apply to all members of the suborder. All the Chalastogastra known 

 to occur in Boulder County have the second anal vein of the fore wings present, and, in 

 most of them, the cubitus of the same wing joins the costa and not the basal vein. 



Superfamily Megalodontoidea 



Posterior margin of the pronotum straight or nearly so, being nearly the shortest 

 distance between the anterior margins of the tegulae; mesonotum short, never extending 

 much beyond the anterior margins of the tegulae; proepimeron wanting. 



This superfamily is known in the county at present by the family Xyelidae. The 

 family Cephidae and subfamily Pamphiliinae (of Megalodontidae) should be found within 

 the county. 



Family XYELIDAE 



First perapterum present, seen a short distance below the tegulae as a small free 

 plate; anterior tibiae with two calcaria; basal joints of the flagellum consolidated so as 

 to form one joint; intercostal vein present; radial cell with two cross-veins; robust 

 species. 



This family is represented in the county by the genus Xyela, but the species of Macro- 

 xyela which feed on elm may be introduced with elms. 



Genus XYELA Dalman 



Antennae 12-jointed; the third joint shorter than the following; malar space present; 

 clypeus truncate; ovipositor of female as long as the abdomen. The larvae and larval- 

 habits of this genus are very imperfectly known. One species belonging to this genus 

 has been bred from young pine cones, and it seems probable that the species are internal 

 feeders and that they may live in the young fruits of various plants. They are found 

 only in the early spring and are very local, appearing for a short time only. It is usually 

 profitable to look for them on willows, alders, box-elder and similar plants when their 

 petals are falling. 



(1) X. negundinis Cockerell. Black; legs below femora pale brown; sheath 

 stout, short, straight below, oblique to the sharp apex above; vertex raised caudad to 

 lateral ocelli; postocellar line distinctly shorter than the ocellocular. 



Female; Boulder, Colorado, collected April 10, 1907, at flowers of Acer negundo, 

 by Cora Bennett. (Type locality.) 



