ichneumon-flies, part 2\ ephialtinae 395 



6. Tribe Rhyssini 



Figures 302,b-304,a 



Front wing 6 to 30 mm. long; clypeus small, subrectangular, with 

 a median apical tubercle and/or lateral apical tubercles; mesoscutum 

 covered with sharp, irregular, transverse wrinkles, in profile usually- 

 flat above and abruptly declivous at front end, its notauli usually 

 long; prepectal carina present except sometimes in Epirhyssa; meso- 

 pleural suture straight or almost straight; propodeum without carinae; 

 last segment of tarsus not enlarged; tarsal claws simple, without an 

 enlarged hair with a flattened tip; areolet present or absent; nervellus 

 broken above the middle; first tergite free from its sternite or fused 

 with it, without a distinct lateral longitudinal carina; male subgenital 

 plate transverse, its apical margin retuse or sometimes truncate; 

 apex of last tergite of female prolonged, ending in a short polished 

 horn that is truncate at the end or in a polished marginal boss; ovi- 

 positor moderately long to very long, compressed. 



The Rhyssini are almost worldwide in distribution. Many of the 

 species are large and spectacular, and are among the best known of 

 all ichneumonids. Our species belong to four genera. 



Key to the Nearctic genera of Rhyssini 



1. First tergite free from its sternite, with a glymrna; second trochanter of middle 



leg without a ventral longitudinal ridge; sternites 3 to 6 of female with 

 a pair of tubercles near their midlength; clypeus with a median apical tubercle 



but without lateral apical tubercles 1. Rhyssa (p. 396) 



First tergite fused with its sternite, without a glymma; second trochanter of 

 middle leg with a ventral longitudinal ridge; sternites 3 to 6 of female with 

 a pair of tubercles near their base 2 



2. Areolet always absent 3. Epirhyssa (p. 41 3) 



Areolet present, rarely absent in abnormal specimens 3 



3. Males 4 



Females 5 



4. Clasper without a groove paralleling its lower inner edge, nor with a longitudinal 



groove apicolaterally; tergites 3 to 6 moderately concave apically, without 

 a median longitudinal submembranous area. (See the note on dwarf males 

 of Megarhyssa in the second half of the couplet.) ... 2. Rhyssella (p. 409) 

 Clasper with a strong setiferous groove close to and paralleling the apical 

 0.7 ± of its lower inner edge, and with a short, longitudinal setiferous groove 

 apicolaterally; tergites 3 to 6 of male strongly concave apically and with 

 a median apical or subapical longitudinal submembranous area. Note: 

 These generic characters hold for normal males, but dwarf males do not have 

 them developed and will key to the genus Rhyssella . 4. Megarhyssa (p. 415) 



5. Tergites 3 to 5 covered with transverse aciculation except laterally. 



2. Rhyssella (p.409) 

 Tergites 3 to 5 entirely or largely without transverse aciculation. 



4. Megarhyssa (p. 4 15) 



