Cloacal smears from the racers examined usually showed an abundance of ciliate protozoans, either parasites or commensals, and occasionally nematode worms. Harwood (1933:66) examined two racers from the vicinity of Houston, Texas, and found four kinds of helminths: _Kalicephalus agkistrodontis_, _K. rectiphilus_, _Ophidascaris_ sp., and _Polydelphis_ sp. Each parasite was found in only one of the two snakes. McCauley (_loc. cit._) recorded nematodes (_Physaloptera obtusissima_) from black racers in Maryland, and Ortenburger (_loc. cit._) recorded _Physaloptera_ sp. from the blue racer. Table 18. Seasonal Incidence of the Fluke Neorenifer lateriporus, in Mouths of Blue Racers on the Reservation and Rockefeller Tract =============+=================+====================== | Number of | Percentage of sample | racers checked | having flukes -------------+-----------------+---------------------- Apr. 15-30 | 1 | 100 May 1-15 | 28 | 79 May 15-31 | 25 | 72 June 1-15 | 24 | 50 June 15-30 | 17 | 18 July | 30 | 0 Aug. | 5 | 0 Sept. | 9 | 0 Oct. | 2 | 0 -------------+-----------------+---------------------- Populations _Composition_ Since there is a brief annual breeding season, any local population of racers consists of a series of discrete annual age groups. The population reaches its annual maximum in early September, after undergoing sudden increase by the addition of the annual crop of hatchlings. Throughout the remainder of the year numbers of racers undergo gradual reduction as a result of the many combined mortality factors that affect them. This mortality is distributed among all the age classes, but the heaviest losses, both percentage-wise and in actual numbers, are sustained by the first-year young. Being by far the most numerous group, these young suffer more mortality than all the other age classes combined. Presumably much of this mortality is concentrated in the early weeks of life, while the young are still near their minimum size; the rate of loss is gradually reduced as larger size is attained and some of the early hazards are outgrown. In the adult age classes also, the larger and older snakes live in greater security, and the rate of mortality is higher in the smaller and younger snakes. Even before hatching, the eggs are subject to heavy losses from predators, and probably from drying, flooding, and other unfavorable climatic factors. Unfortunately it was not possible to obtain definite figures on any of these losses since the eggs were never found under natural conditions and the hatchlings were seen only in relatively small numbers.