14 species, according to Tree of Life.
Nomina Nearctica lists only three species.
"The thorax is humpy. This is characteristic of Tegeticula, whereas Prodoxus has a smaller thorax that tapers off further with the head. I sometimes refer to their resting profiles as 'race car' (Prodoxus) and 'bulldog'." (Dr. Olle Pellmyr)
Some species have orange legs.
The fascinating relationship between yucca moths (genus Tegeticula) and yucca plants (genus Yucca) is one of the celebrated examples of mutualistic plant-insect interactions. Its discovery and fascinating details are richly presented in the links and articles cited below under "Print References".
D.M. Althoff, K.A. Segraves, C.I. Smith, J. Leebens-Mack, & O. Pellmyr (2012). "Geographic isolation trumps coevolution as a driver of yucca and yucca moth diversification". Mol. Phylogenet. Evol., 62(3), pp. 898–906 (PDF
M. Ramsay & J. R. Schrock (1995). "The Yucca Plant and the Yucca Moth", Kansas School Naturalist, 41(2), pp.1-13 (Full Text
O. Pellmyr, J.N. Thompson, J.M. Brown, & R.G. Harrison (1996). "Evolution of pollination and mutualism in the yucca moth lineage". Amer. Nat., 148(5), pp 827-847 (PDF
Pellmyr, O. (2003). "Yuccas, yucca moths and coevolution: a review". Annals of the Missouri Botanical Garden, 90:35-55. (PDF
C.A. Sheppard & R.A. Oliver (2004). "Yucca Moths and Yucca Plants: Discovery of 'the Most Wonderful Case of Fertilisation'". Am. Entomol., 50(1) pp. 32-47 (PDF
C. R. Smith (2010). "Coevolution of Joshua trees and their Pollinators". Mojave National Preserve Science Newsletter, Number 1, pp. 4-8 (PDF
The Yucca and its Moth
from "Waynes Word" by Wayne Amrstrong.