58 



out the area; interspecific competition is implicated. Plains habitats 

 are preferred by gularis , inornatus and tigris whereas roughland habi- 

 tats are preferred by exsanguis and tesselatus . Competition between a 

 species in its preferred habitat and one "invading" it (i.e. not in the 

 invader's preferred habitat) almost always occurred between a sexual 

 and a parthenogenetic species. Intraspecific aggression occurred, par- 

 ticularily in inornatus , but not on a predictable basis. Interspecific 

 aggression did not occur, although lizards did meet and notice one an- 

 other. Territoriality was not evident. It was found that a meeting 

 between two lizards is not a common occurrence even where lizards are 

 numerous. Species and geographic differences existed in prey consump- 

 tion; in general, Isoptera > Orthoptera > Coleoptera > Lepidoptera> 

 Hemiptera. Termites are by far the most important food item and may be 

 regarded as the staple food for all species; indeed, the genus is adap- 

 ted morphologically for this. Competition for the staple food source 

 is the only obvious explanation for the ecological separation of the 

 species, because size differences and alternate food differences do not 

 allow them to coexist. Differences in foraging activities reflect tem- 

 perment; inornatus is not easily excited whereas tigris is very nervous 

 and wary, the other species falling between these extremes. Lizards 

 are active only when soil temperatures range between 30-50°C. No 

 interspecific differences in reproduction were observed; multiple 

 clutches are indicated. No competition exists with other lizard 

 genera, they are essentially ecologically invisible. It is possible 

 that individual Cnemidophorus species that are in competitive asso- 

 ciations mutually inhibit their own potential increase more than that 

 of the other species and thus can continue to coexist. If, as pre- 

 sumed in this study, no species has an advantage or if reciprocating 

 ones exist, it may be predicted that all 5 species will continue to 

 exist in the Chihuahuan Biotic Province, but weight of numbers or 

 chance will eventually remove all but one of them from any given as- 

 sociation within the province. 



156. — . 1958. A list of arthropods found in the stomachs of whip- 

 tail lizards from four stations. TEXAS 3. SCIENCE lO(^): ^^3-'f'f6. 



A list as precise taxonomically as possible of the food items 

 eaten by ll'fl lizards ( exsanguis , gularis, inornatus , tesselatus and 

 tigris) is presented. Taxa are indexed relative to lizard predator and 

 specific locality. No millipedes or lubber grasshoppers (Taeniopoda 

 eques ) and only 1 meloid beetle were eaten, indicating unpalatibility. 



157. — . 1959. Drift-fence trapping of lizards on the Black Gap 

 Wildlife Management Area of southwest Texas. TX. 3. SCI. 11: 150-157. 



The method of trapping and weather conditions in the mesquite- 

 huisache association are described. Cnemidophorus inornatus , _C. tigri: 

 and four other species were trapped. No inornatus were recaptured. 31 



