1977] 
Porter — Mesostenines 
29 
and Mr. Antonio Salinas (Park Ranger 3) maintained the Malaise 
Trap used in my 1976 survey and provided cordial assistance on all 
my visits to the park. Mrs. Vivian Thacker, as trustee of the Valley 
Botanical Garden, facilitated collecting in that small but important 
island of natural vegetation. My father, Mr. Carroll B. Porter, also 
assisted in the Malaise project and in many other ways. Mr. Charles 
W. Calmbacher of Fordham University prepared and labeled most 
of the Malaise samples from Bentsen Park. Finally, Dr. Henry K. 
Townes of the American Entomological Institute loaned several 
homotypes which helped resolve crucial taxonomic problems. 
Materials and Methods 
Hand collecting with a strong but light net obtained 63% of the 
679 specimens captured between May 1973 and March 1977 for use 
in this study. Sweeping undergrowth yielded numerous mesoste- 
nines but many others were netted individually in flight from foli- 
age. Periods annually available for fieldwork included 25 August 
to 9 September, 18 December to 25 January, 11-21 March (1-8 
April in 1975) and 16 May to 10 June. I was in the field 7 days a 
week and 6-8 hours per day during all visits to south Texas. 
To obtain a more comprehensive picture of mesostenine diversity 
than would have been possible by hand collecting alone, I employed 
two Malaise Traps during this research. The first was installed at 
the Valley Botanical Garden in a Celtis lindheimeri-C. pallida thicket 
and functioned from September 1973 until March 1974 but was 
stolen in April 1974. The second was set up under a large Pithecel- 
lobium flexicaule in deep woods near a lake at the Bentsen Rio 
Grande Valley State Park and, having already furnished a complete 
series of samples for 1976, continues to operate during 1977. In both 
traps, a pint mason jar filled with 70% isopropyl alcohol (commer- 
cial rubbing alcohol) was used as the collecting recipient. The trap 
at the Botanical Garden was changed once a month but I was able 
to arrange for twice monthly curating of the Bentsen Park trap. 
Both Malaise Traps were of the “light weight” variety, as perfected 
by Dr. Henry K. Townes (Townes, 1972, p. 239-247). 
The Study Area 
The Lower Rio Grande Valley is an alluvial plain that extends 
along the Rio Grande River for about 120 km. in Hidalgo and 
