1. Department of Mathematics, University of Arizona, 617 N. Santa Rita Ave., Tucson, AZ 85721 (lega@math.arizona.edu)
2. Corresponding author, e-mail: lega@math.arizona.edu
3. Mel and Enid Zuckerman College of Public Health, University of Arizona, 1295 N. Martin Ave., Tucson, AZ 85724 (heidibrown@email.arizona.edu)
4. Entomology and Ecology Activity, Dengue Branch, Centers for Disease Control and Prevention, 1324 Calle Cañada, San Juan, Puerto Rico 00920 (amz9@cdc.gov)