86 
Psyche 
[March 
tween September and April, while the winter months are almost 
rainless and bring repeated killing frosts. Rainfall and temperature 
thus regulate the seasonal cycles of both Subandean and south 
Texan mesostenines but the annual climatic pattern is totally dif- 
ferent in each area, producing an invernal peak in the Valley and 
a vernal maximum in the Subandino. 
During 1973, I maintained a Malaise Trap at General Saavedra 
near Santa Cruz de la Sierra, Bolivia. Saavedra lies at about 18 
degrees S. Lat. and less than 400 m. altitude toward the humid 
extreme of an ecotone between Chaco scrub and the southernmost 
Amazon Basin rainforest. My trap was in wet forest under deep 
shade of cecropias, palms, philodendrons and other “tropical” flora. 
Monthly Malaise records for Saavedra include 6 species and 8 spec- 
imens for January, 3 species and 4 specimens for February, 3 species 
and 3 specimens for March, (April sample lost), 4 species and 8 
specimens for May, 8 species and 9 specimens for June, (July sam- 
ple lost), 19 species and 35 specimens for August, 5 species and 1 1 
specimens for September, 5 species and 6 specimens for October, 
9 species and 18 specimens for November, and 2 species and 4 speci- 
mens for December. Furthermore, hand collecting at Saavedra 
in July yielded 41 species and more than 100 specimens of Meso- 
stenini. This fauna consequently peaks during mid-winter and is 
much scarcer at other times of the year, showing considerable phae- 
nologic resemblance to the Valley fauna. I have no weather data 
for Saavedra but infer from its flora that the area receives at least 
1500 mm. of rain per year. Summer is the warmest and wettest 
season but all months have significant precipitation and the winter, 
although relatively dry, is punctuated repeatedly by cold fronts 
that may bring 5-10 days of persistent drizzle. July and August 
temperatures range from nightly lows of 10-15 degrees C. to daily 
highs of around 30 degrees C. but cold fronts may bring minima 
of 3 degrees C. with mid-day maxima of no more than 12 degrees 
C. Summer temperatures probably show an average daily range 
of 25-38 degrees C. The Saavedra climate thus is a little warmer 
and much wetter than that of the Valley but shows much the same 
type of variation from month to month and, evidently, has a rather 
similar effect on the ichneumonids under its control. 
Habitat Selection 
Of the 34 Valley mesostenine species collected, 21 were taken 
only in partly to densely shaded woods with considerable under- 
