and east, the other to the west. Description Ranging in size from in length, the western cicada killer is very similar to its eastern cousin, Sphecius speciosus, with a rufous black hue to the body, amber stripes and a yellow abdomen. The western cicada killer has rufous spots on its first to second tergites and yellow markings can generally be found from first to fifth, although there is some variation. On average, female forewing length lies between . Females are larger than males and live for a year, a time just long enough to produce a brood, whereas the males die in only a few days, just enough time to impregnate a female. In Steven J. Phillips' book A Natural History of the Sonoran Desert, he referred to them as superficially resembling "huge yellowjackets or hornets" and stated that they are "powerful fliers with compound eyes". On average, males weigh 95mg and females are far heavier, at 256mg, probably because of the additional weight of the ovaries, developing eggs and nutritional reserves. Nevertheless, the ratio between flight muscle mass and body mass is the same for both sexes. Identification Distinguishing S. grandis from the other four New World species of Sphecius (S. convallis, S. hogardii, S. speciosus, S. spectabilis) is difficult. The female S. convallis was originally distinguished from the female S. grandis by the yellow marks from the first to third gastral tergites on S. convallis and yellow marks on all tergites for S. grandis. However, this was found to be insufficient for correct identification because the positions of the markings can vary among different wasps of the same species. Charles W. Holliday and Joseph R. Coelho devised a new key in 2004 to identify the Sphecius species, examining 4,451 wasps among the five New World species, and noting that 98% of the female S. convallis wasps examined had yellow markings on gastral tergites one to four (or fewer) and S. grandis had 98% yellow markings from tergites one to five (or more). The 2% percent of S. grandis that overlapped with S. convallis were determined by density of the punctation in colour of the first tergum against the second. The markings on S. grandis males were found to be the same as on females. Thermoregulation It has been found that the western cicada killer wasp is capable of thermoregulation which enables them to maintain territories during the day.