76 
Psyche 
[March 
Conclusions 
Zoogeography 
The 18 Valley mesostenine genera fall into three zoogeographic 
categories: Neotropic, Sonoran, and Holarctic. Neotropic genera 
are Latin American taxa with centers in the Brasilian Highlands, 
the Andean Cloud Forests, and the mountains of Middle America. 
The Sonoran group includes genera which originated along the 
Madro-Tertiary geoflora in the southwestern U.S. and northern 
Mexico. The Holarctic element is circumpolar with maximum de- 
velopment in Temperate Deciduous Forests. Ten Valley genera are 
Neotropic: Cryptanura, Bicristella, Diapetimorpha, Mallochia, Ly- 
me on, Acerastes, Polycyrtidea, Pachysomoides, Messatoporus, and 
Agonocrvptus; four genera are Sonoran: Joppidium, Lanugo, 
Compsocryptus, and the Longicaudis group of Mesostenus; and 
five are Holarctic: Gambrus, Trvchosis, the Transfuga group of 
Mesostenus, Listrognathus, and Trachysphyrus. 
The Neotropic group requires special comment. This fauna pre- 
dominates at the generic level, includes 22 of the 35 species re- 
ported, and accounts for 543 of the 679 specimens collected. 
Although the modern Neotropic radiation is centered in Latin 
American humid forests, only one of the genera cited, Bicristella, 
reaches its northern limit in the Valley; all others range farther 
into North America, where they inhabit principally the southeast. 
This northeastern group seems descended from a larger and more 
pervasive Middle and North American Tertiary fauna that was 
pushed south by Pleistocene glaciations. During glacial maxima, 
a few of these Neotropic elements survived in the southeastern 
U.S., while many retreated southwest into the more hospitable 
lower latitudes of Middle America. Interglacials allowed some 
expansion from Pleistocene refugia but the accompanying aridity 
in subtropic latitudes has slowed movement of moisture-loving 
ichneumonids. Thus, southeastern isolates have expanded with 
the Temperate Deciduous Forest and Southern Pine-Oak Forest 
as far north as Maryland or New Jersey and southwest into Texas, 
while some Mexican species have followed subtropical deciduous 
woods into Texas. However, the semiarid scrub now covering 
much of south Texas and northeast Mexico has prevented mas- 
sive interchange between the present-day Middle American and 
southeast North American Neotropic faunas. 
