Occasional Papers of the Museum of Zoology 31 



Postnodals hind wing male, Colombia 14 to 16; Canal Zone 

 14 to 15. 



Postnodals front wing female, Colombia 15 to 16; Canal 

 Zone 17 to 18. 



Postnodals hind wing female, Colombia 13 to 15; Canal 

 Zone 14 to 15. 



Thus the difference between the lengths of the abdomen of 

 the largest and smallest males is 8 mm., and of females 5 mm. 

 Xo other species shows such variation in size. The profile is 

 similar in both sexes. 



Under initatriini some habits of crythrogastruui are noted. 

 V\'e found it commonly along all the streams at Cristalina 

 excepting the Rio Diez-y-ses where we did not see it during 

 the single day we collected there. It is a relatively conspicu- 

 ous insect, the blood red abdomen contrasting strongly with 

 the green and browns of its environment, as it rests with half- 

 spread wings on twig tips. The wings vary from clear to 

 brown or dingy tinged. We observed it about Cristalina 

 from about 8 or 9 a.m. till nearly 5 p.m. when the ravines were 

 dark and gloomy. A male, taken at Cristalina, has the abdom- 

 en turned once on its long axis at the sixth segment, hke a 

 corkscrew. We took a number of ]\Iecistogasters similarly 

 malformed. Evidently during emergence from the exuvia, be- 

 fore the apical abdominal segments are released, the soft 

 teneral, agitated by some cause and attached to the exuvia only 

 by the apical segments, is twisted or turned, producing the 

 corkscrew malformation of the adult. 



Material Studied : This species is well represented in sever- 

 al collections ; I have examined 194 males and 35 females. To 

 the locahties recorded by de Selys (2), Calvert (3), and Ris 

 (8) , the following may be added : Costa Rica : Bonnefil Farm, 

 Rio Surubres, 700 feet; Rio Siquiares; Turrucares, 



