Male ~ Female
Colorado Desert, Riverside County
Habitat of Dinacoma caseyi Blaisdell
Although provided with fully developed metathoracic wings, female Dinacoma do not exhibit flight behavior. Similar behavior has been observed in some species of closely related Melolonthini including Polyphylla Harris, Thyce LeConte, and Amblonoxia Harris, among several others. It has been posited that loss of flight is favored among females because it permits greater allocation of metabolic resources toward production of ova while flight is retained in males because it increases the probability of mate location. This is supported by the fact that males have larger antennal structures and longer lamellate antennomeres, therefore greater surface area. For this reason, males are presumed to have a superior ability in chemoreception of pheromones emitted by prospective mates.
Other theories suggest an evolutional preference to flightlessness where dispersal ability is not essential toward long term survival of species in ecologically stable environments ("environmental homogeneity" Roff 1990). Thus, the success of progeny is enhanced by preserving genomes that are favorable in the existing environment. Moreover, among desert insects, flightlessness may have evolved because dispersing individuals experience high rates of mortality as well as higher desiccation from flight activity (Wagner and Liebherr 1992).
La Rue, D.L. 1998. Notes on Polyphylla Harris with a description of a new species. (Coleoptera:Scarabaeidae:Melolonthinae). Insecta Mundi 12(1/2):23-37
Roff, D. A. 1990. The evolution of flightlessness in Insects. Ecological Monographs 60(4):389-421.
Wagner, D. L. & Liebherr, J. K. 1992. Flightlessness in Insects. Trends in Ecology and Evolution 7:216-220.
Woodruff, R.E. 2004. Revision of the Phyllophaga of Hispaniola (Scarabaeidae: Melolonthinae). Insecta Mundi 18(1-4):1-154.