NO. I ACKNOWLEDGMENTS Vll 



To the several specialists, mentioned in various sections of this 

 paper, who so generously gave of their time and experience to deter- 

 mine plants and animals for me. 



To Dr. Luis Vargas, chief of the Laboratory of Entomology of the 

 Instituto de Salubridad y Enfermedades Tropicales in Mexico City, 

 who so kindly placed at my disposal for a 5-week period the services 

 of his laboratory and his personnel, and who has always been eager 

 to discuss matters concerning the black flies of Mexico and Guate- 

 mala, supplying specimens when requested. 



To Dr. Alan Stone, Entomology Research Branch, U. S. Depart- 

 ment of Agriculture, for his generosity in supplying simuliid specimens 

 for making comparisons, and for his helpful suggestions and criticisms. 



To Dr. E. A. Chapin, former curator. Division of Insects, United 

 States National Museum, for his kindness in having printed and 

 supplying me with insect pin labels. 



To W. H. W. Komp, Laboratory of Tropical Diseases, National 

 Institutes of Health, for his interest and helpful suggestions, espe- 

 cially in regard to a possible technique for inducing oviposition of the 

 flies. 



To Miss Ruth Secor, administrative assistant, Laboratory of Tropi- 

 cal Diseases, for her unending attention to my administrative and 

 personal problems. 



To Dr. Thomas A. Burch, medical officer; Dr. Colvin L. Gibson, 

 parasitologist; and Arden O. Lea, Jr., assistant entomologist of the 

 Onchocerciasis Project, for the suggestions, criticisms, and personal 

 kindnesses they so generously bestowed during our close and extended 

 association in Guatemala. 



To Angel Ruiz, for his untiring attentions to the secretarial aspects 

 of the Onchocerciasis Project. 



To Francisco Camino P. and Rony Alvarado, who so ably prepared 

 the diagrams used in this monograph. 



To Dr. Willard H. Wright, chief of the Laboratory of Tropical 

 Diseases of the National Institutes of Health, who was instrumental 

 in establishing this project, for his constant encouragement, both 

 scientific and personal, for his understanding of our problems, and 

 for his generosity in the procurement of supplies and literature. 



To my wife, for her loyalty, her faith in the work I was doing, 

 her assistance in the arrangement of the material for this manuscript, 

 and her painstaking reading of the paper. 



H. T. D. 



