PICROCRYPTOIDES: A NEW GENUS OF THE 
TRIBE MESOSTENINI FROM SOUTHERN SOUTH 
AMERICA (HYMENOPTERA, ICHNEUMONIDAE)* 
By Charles C. Porter 
Biological Laboratories, Harvard University 
The ichneumonid genus Trachysphyrus Haliday and its close rela- 
tives within the huge tribe Mesostenini are found in almost every part 
of the world. With one exception, however, the greatest number of 
these species seems limited to the Holarctic region. This exception 
is temperate and subtropical South America. 
The ancestors of the present-day South American Trachysphyrus 
fauna appear to have entered the southern continent from the north. 
In tropical countries, such as Ecuador and Peru, they radiated only 
at high altitudes in the Andes (approximately 8,000 to 14,000 feet) 
and, to a lesser extent, in the coastal desert and foothills on the west. 
None, so far as known, penetrated the tropical cloud-forest and rain- 
forest at lower elevations to the east. In the temperate regions of 
central and southern Argentina and Chile, on the contrary, this 
generic group of north-temperate extraction found a more suitable 
area in which to expand and produced a very complex radiation of 
close to 100 species, probably more than occur in any area of similar 
size and, certainly, in greater variety than in any other region which 
the Trachysphyrus Group inhabits. 
Among this Argentine and Chilean radiation are many species- 
groups which depart more or less radically from the customary 
definition of the genus Trachysphyrus. Some, although superficially 
bizarre in aspect, are not clearly to be distinguished from the main 
genus, to which they are often connected by species of intermediate 
character. Much of the group is still evolving rapidly and generic 
lines are not always clearly defined. Other series, however, present 
a combination of unusual features which so isolates them from their 
relatives that it would seem natural and convenient to place them in 
separate genera. One such group, the new genus Picrocryptoides, is 
diagnosed below together with a description of its two known species. 
Picrocryptoides, new genus 
Antenna: unusually short and stout: in 9 subtly enlarged and slightly 
flattened below toward apex, first flagellomere about 3.2 to 3.8 times 
* Manuscript received by the editor April 19, 1965 
167 
