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Comparison of diets of two syntopic lizards, Aspidoscelis marmorata and Aspidoscelis tesselata (Teiidae), from the northern Chihuahuan Desert of Texas.

Interspecific competition is the interaction among individuals of two or more species which utilize the same limited resource (Pianka, 1988). Competition can be mediated either by direct interaction (interference) or by resource depression or depletion (exploitative; Pianka, 1988). Ecologists have been interested in competitive interactions between closely related species for many years, although the ramifications of those interactions are still not clearly understood (Levins, 1968). The utilization of similar niches seems to be in conflict with the competitive exclusion principle, which holds that two or more species cannot permanently coexist if they have identical ecological needs (Levin, 1970).

Whiptail lizards (Aspidoscelis) of the family Teiidae are a taxonomically diversified group achieving highest species richness in the southwestern United States and northern Mexico (Wright, 1993). Also, the genus Aspidoscelis possesses many parthenogenetic species, and species of both reproductive modes often share similar habitats, even when sympatric (Schall, 1993). Such intimate coexistence among sympatric species of Aspidoscelis has prompted several ecological studies designed to understand the patterns of resource utilization and partitioning of resources (see review by Schall, 1993).

According to Pianka (1973), lizards as a group partition resources by being active at different times, foraging in different places, and feeding on different types of prey. However, information gleaned from investigations into resource partitioning in Aspidoscelis revealed that many sympatric species are essentially active at the same times of day, eat similar food items, and possess similar foraging behavior. The major factors preventing total competition appeared to be the options of living in different microhabitats or in different geographical areas (Milstead, 1957; Mitchell, 1979), although there was reported overlap in those as well (Cuellar, 1979). Subtle partitioning also might result from different foraging behaviors or because of discrepancies in body size (Medica, 1967; Scudday and Dixon, 1973; Case, 1983), but the latter was not observed by Taylor et al. (2011).

Food is obviously an essential ecosystem component that influences individual survival and reproductive success in living populations (Ballinger, 1977). Consequently, the main purpose of our study was to compare similarities and differences in diets within and between two syntopic species of whiptail lizards occurring in the Chihuahuan Desert of Trans-Pecos Texas. The two species were Aspidoscelis marmorata, a bisexual species represented by male and female individuals and Aspidoscelis tesselata, a unisexual species represented only by females.

Aspidoscelis marmorata and A. tesselata share a number of morphological and behavioral characteristics, presumably resulting from the contribution of A. marmorata genome to A. tesselata during its hybrid origin (Neaves, 1969; Reeder et al., 2002; Cordes and Walker, 2003). We assumed that there might be differences in selection of prey allowing the two species to successfully coexist in the same place if the competitive exclusion principle (Hardin, 1960) were operating. That is, if two syntopic species utilize the same limited food resources, they should be forced to compete for those resources, with possible outcomes being resource partitioning, character displacement, species dislocation, extinction, or a combination thereof.

Previous studies on composition of diet found that A. marmorata and A. tesselata are generalist consumers that tend to feed most often on termites, if available (see review by Schall, 1993), although disparity in diet also has been reported (Medica, 1967; Saxon, 1970). Guerra (1995) found significant sexual dimorphism in A. marmorata and Schoener (1967) previously suggested that sexual dimorphism might be caused by competition for food resources and by each sex exploiting different microhabitats.

MATERIALS AND METHODS--We conducted our study within The University of Texas at El Paso's (UTEP) 16,187-ha Indio Mountains Research Station (centered on 30.67[degrees]N and 105.00[degrees]W) in southeastern Hudspeth County, Texas, about 40 km southwest of Van Horn. The vegetation in the study area was typical Chihuahuan Desert scrubland, dominated by creosote bush (Larrea tridentata), lechuguilla (Agave lechuguilla), ocotillo (Fouquieria splendens), catclaw (Acacia greggii), white thorn acacia (Acacia constricta), honey mesquite (Prosopis glandulosa), and Eve's needle (Yucca faxoniana), as well as grasses represented by tobosa grass (Hilaria mutica) and black gramma (Bouteloua eriopoda). The annual precipitation on the site was typically <25 cm/year, with most falling during the summer monsoon season, lasting from June through September (Johnson, 2000).

Lizards were collected during regular trips to the study site from mid-June through mid-October 2004 and from mid-May through July 2005. The array of pitfall traps used to collect lizards consisted of 30 five-gallon buckets with screw lids and wood covers, covering an area of ca. 8,000 m2. Live specimens were examined to determine their sex, weighed with a MP-500 portable scale to the nearest 0.1 g, and measured for snout-vent length and tail length to the nearest 1.0 mm with a ruler and for head width, length, and height to the nearest 0.1 mm with a caliper. Lizards were euthanized using an overdose injection of sodium pentobarbital (60 mg/kg) into the thoracic cavity. Euthanized lizards were fixed by internal injection of 10% formalin, allowed to harden, tagged for later identification, and washed with water before being placed into 70% ethanol for permanent preservation. All preserved lizards were deposited into the Herpetology Collection, Laboratory for Environmental Biology, Centennial Museum, The University of Texas, El Paso: A. marmorata: UTEP 19366-67, 19369, 19373-81, 19383-85, 19387-92, 19395-437, 19439-55; A. tesselata,; UTEP 19332-39, 19341-44, 19346-47, 19354-55, 19357, 19360-64. Protocols were approved by the UTEP Institutional Animal Care and Use Committee (No. A-1940).

Size at sexual maturity for females of both species was based on the smallest individuals containing vitellogenic follicles, corpora lutea, or oviductal eggs. Size at sexual maturity of males was estimated based on presence of enlarged testes and convoluted epididymides (Vitt et al., 1997). Statistical analyses were performed with Systat version 10.2 (SYSTAT software Inc., 2002). We measured snout-vent length, head length, head width, and head height in millimeters and body mass in grams to compare body proportions between males and females. We used regressions of log10 transformed data to determine if relationships were indicated between variables. A Mann-Whitney U-test was performed on morphological characteristics to assess for statistical differences at [alpha] = 0.05. Means ([+ or -]1 SE) are presented. Arthropods occurring in the area surrounding pitfall traps were surveyed on a regular basis to facilitate identification of food items in stomachs of lizards.

Stomachs of lizards were removed and dissected, and their contents were identified with a dissection microscope. The total volume of contents for each lizard was determined by water displacement in a 10-cc graduated test tube (Schall, 1993). Contents were separated by food groups identified taxonomically at least to order. The number of different prey items and their measurements (body length and width) also were taken. We determined volumes of different classes of prey by the formula for spheroid shapes: V = 4/3IT (length/2) x (width/ 2)2 (Vitt and Carvalho, 1992). Proportions of classes of prey were compared between the two species. That information was used to determine relative abundance (average percentage of type of prey per stomach), relative volume (percentage of total volume for every type of prey) and prey incidence (percentage of stomachs containing a determined category of prey), as described by Maury (1981).

Food-resource breadth was estimated between the two species, with the assumption that 0 was assigned to strict specialists and a value of 1 to strict generalists. We used the formula suggested by Levin (1968) B = 1 / [summation][p.sub.ij.sup.2], where B = niche breadth and [p.sub.ij] = proportion of food items (i) in the diet of spectrum (j). Overlap values of exploited food resources were calculated by [O.sub.JK] = [summation][P.sub.ij][P.sub.ik] /

[square root of ([summation][P.sup.2.sub.ij] [summation] [P.sup.2.sub.ik])], where [P.sub.ij] = proportion of individuals of the species j that use the resource i, and [P.sub.ik] = proportion of individuals of the species k that use the resource (Pianka, 1973).

RESULTS--A total of 106 adult lizards (82 A. marmorata and 24 A. tesselata) were collected and compared for body weight, body proportions, and food contents. Eleven males and two females of A. marmorata and three females of A. tesselata had empty stomachs; therefore, diet comparisons were based on 69 A. marmorata and 21 A. tesselata.

Adult body mass of A. marmorata ranged from 7.5-24.6 g for males and from 10.2-17.2 g for females. Body mass in A. tesselata ranged from 8.4-25.4 g. There was no significant difference in body mass among the two sexes of A. marmorata and female A. tesselata (Table 1).

Snout-vent length of adult A. marmorata ranged from 67-94 mm for males and from 75-87 mm for females, whereas that for adult female A. tesselata ranged from 66-94 mm. Mean snout-vent length was slightly higher for male A. marmorata than for females of both species, but the difference was not statistically significant. Significant differences in head length, width, and height were found only between male A. marmorata and female A. tesselata (Table 1).

Food consumed by A. marmorata was identified to 14 orders, while food consumed by A. tesselata was identified to eight orders. Both sexes of A. marmorata ate more individual isopterans (93.5% in males; 83.8% in females) than all other taxa combined. By volume, 84.3% of the diet of male A. marmorata was comprised of Homoptera (37.8%), Orthoptera (18.0%), Isoptera (16.6%), and Araneae (11.9%), whereas 91.3% of the diet of female A. marmorata was comprised of Araneae (54.1%), Hymenoptera (27.2%), and Homoptera (10.3%). Female Aspidoscelis tesselata consumed more individual isopterans as well (94.6%). By volume, Orthoptera (29.8%), Ho moptera (29.7%), Araneae (16.6%), and Isoptera (16.2%) composed 92.3% of the diet in A. tesselata (Table 2).

There was no significant linear relationship (P > 0.05) between prey volume and snout-vent length, head width, head length, or head height for male ([R.sup.2] = 0.3, [F.sub.1,58] = 0.20; [R.sup.2] = 1.5, [F.sub.1,58] = 0.91; [R.sup.2] = 0.4, [F.sub.1,58] = 0.23; [R.sup.2] = 0.8, [F.sub.1,58 = 0.47, respectively) or female A. marmorata ([R.sup.2] = 2.7, [F.sub.1,7] = 0.19; [R.sup.2] = 0.9, [F.sub.1,7] = 0.06; [R.sup.2] = 14.9, [F.sub.1,7] = 1.23; [R,sup.2] = 9.6, [F.sub.1,7 = 0.74, respectively). With regard to A. tesselata, there was no significant linear relationship (P > 0.05) between prey volume and snout-vent length, head length, or head height ([R.sup.2] = 15.6, [F.sup.1,19] = 3.52; [R.sup.2] = 16.9, [F.sub.1,19 = 3.87; [R.sup.2] = 11.7, [F.sub.1,19 = 2.53, respectively), but there was a significant relationship with head width ([R.sup.2] = 23.9, [F.sub.1,19] = 5.97, P = 0.024).

Male and female A. marmorata consumed isopterans most often (65 and 78%, respectively), followed by homopterans (33 and 22%), coleopterans (30 and 56%), orthopterans (27 and 33%), and arachnids (20 and 44%). Other prey, such as hemipterans, lepidopterans, hymenopterans, pseudoscorpions, chilopods, solpugids, thysanurans, odonates, and dipterans, were found in much lower percentages in lizards of both sexes (Table 3).

The same pattern was observed for female A. tesselata, with isopterans consumed most often (71%), followed by orthopterans (43%), homopterans (33%), coleopterans (24%), and arachnids (24%). Other prey items, such as lepidopterans, hymenopterans, pseudoscorpiones, and chilopods, were found in much lower percentages (Table 3).

With respect to dietary breadth, male and female A. marmorata showed low values (0.162 and 0.314, respectively) as did A. tesselata (0.132). However, dietary overlap values for male and female A. marmorata were higher (0.997) by number of prey, and lower (0.390) by volume of prey. Overlap values between females of both species also were higher (0.997) by number of prey and lower (0.434) by volume of prey. Finally, overlap values between male A. marmorata and female A. tesselata were high for number (0.999) and volume (0.944) of prey.

DISCUSSION--In general, A. marmorata (bisexual) and A. tesselata (unisexual) are similar in body weight, body proportions, and diet in the Chihuahuan Desert on Indio Mountains Research Station. Except for differences in head length, width, and height between male A. marmorata and female A. tesselata, there was no significant difference between the two species in the other characteristics of body size. Although males of A. marmorata were larger than females, the difference was not significant. Case (1983) hypothesized that body size is important in determining which species of whiptail can coexist. In Baja California, two species commonly existed at the same site but were different in body size. Aspidoscelis tigris was often one of the species in a pair and varied greatly in body size, being the smaller of the two in some locations, but larger in other places. Case (1983) also examined body size of coexisting species at sites in Texas, including in the Trans-Pecos region, and found that body size was important in the more numerically complex assemblages of Aspidoscelis there. However, Schall (1993) did not find differences in size in his study of coexisting A. marmorata and A. tesselata, a result also determined in our study. However, Taylor et al. (2001) reported gravid individuals of A. tesselata to be significantly larger than gravid females of A. marmorata in New Mexico.

We found an assortment of prey consumed by A. marmorata and A. tesselata that were generally similar to that reported for other species of Aspidoscelis found elsewhere (Schall, 1993). Based on number of individuals, termites were the primary prey. However differences were more evident when prey was analyzed by volume. In our study, while the diet of A. marmorata by volume was represented mostly by cicadas, spiders, grasshoppers and termites, respectively; the diet of A. tesselata was represented mostly by grasshoppers, cicadas, spiders, and termites, respectively. Our results also differed from those of Schall (1993). He reported that A. marmorata consumed mostly termites and beetles and A. tesselata consumed mostly Lepidoptera larvae, beetles, and termites. Even though several studies have determined that termites are the principal prey of whiptails in some areas of the southwestern United Sates (e.g., Milstead, 1965; Scudday and Dixon, 1973; Schall, 1993; Paulissen et al., 2006), this was not the case at other localities (e.g., Dixon and Medica, 1966; Medica, 1967; Milstead and Tinkle, 1969; Taylor et al., 2011).

Only arthropods were consumed by both species on Indio Mountains Research Station. Sand grains were found in stomachs of some individuals but were assumed to be inadvertently consumed while ingesting arthropods. As reported for other species of Aspidoscelis (see review in Schall, 1993), A. marmorata and A. tesselata exhibited a low diversity of prey consumed because of their focus on termites, but they used other arthropods when opportunities arose. The higher volumes of food recorded for species other than termites were the result of the pronounced difference in body size between them.

Cicadas, including cicada molts, were consumed by both species, and their presence shows the ability of these two species to shift their diet and feed on prey that become seasonally abundant. Although ants were very abundant at Indio Mountains Research Station, they were consumed in very low concentrations by both species, a situation also reported by Scudday and Dixon (1973) and Schall (1993). Therefore, it appears that ants are normally avoided by whiptails as potential sources of food.

Early in the yearly activity periods of A. marmorata and A. tesselata, fewer species were found in their stomachs, and certain groups such as cicadas and grasshoppers (Trimerotropis) were absent. This reflects opportunistic consumption controlled by seasonal activity of the prey's life cycle (Echternacht, 1967; Taylor et al., 2011). Milstead (1965) suggested that, during dry years, lizards would feed mostly on termites and, during wet years, more vegetation would increase the variety of insects for food. Although statistical differences in head size were found between male A. marmorata and female A. tesselata, a correlation of head width and volume of prey was observed only in the latter species. Our overlap values were high (>0.9) and similar to that for other species of Aspidoscelis in other areas of the southwestern United States (Milstead 1957; Medica, 1967; Schall, 1993; Taylor et al., 2011). In our study, food overlap was high (mostly termites); this was likely due to their diurnal activity, use of similar microhabitats, similarities in body size, or a combination of some or all of these factors. Negative consequences of this pattern of overlap are probably most critical during years when food availability is low, which was not the case during our study.

The question of what specific factors allow coexistence remains basically unanswered, primarily because different literature sources support contrasting responses. Scudday (1971) examined an assemblage of Aspidoscelis assemblage from another area of Trans-Pecos, Texas, and concluded that species were subjected to cyclical sympatry during which time the composition of species was unstable and never reached an equilibrium competitive stage. According to Paulissen et al. (1992), even if competition occurs, parthenoforms may still coexist with bisexual species if some other factor confers a compensatory advantage to the parthenoforms. Other researchers have suggested that species reproducing by parthenogenesis can increase their population sizes more rapidly than can bisexual counterparts because they do not waste reproductive effort on producing males (e.g., Wright and Lowe, 1968). Results on reproductive characteristics obtained from the same specimens analyzed herein for food (Mata-Silva et al., 2010) and a study by Taylor et al. (2001) revealed differences in clutch size between these two species; A. tesselata had larger clutch sizes. However, Schall (1978) did not find significant differences in reproductive strategies (clutch size, egg weight, and reproductive effort) between bisexual and unisexual species of Aspidoscelis in Trans-Pecos and concluded that similarities were due to constraints imposed by resemblance in body form, foraging technique, and body size.

Behavioral differences between A. marmorata and A. tesselata have been described elsewhere (Echternacht, 1967; Price, 1992; Hotchkin and Riveroll, Jr., 2005). Echternacht (1967) and Scudday and Dixon (1973) concluded that subtle resource partitioning also might result from different foraging behaviors. According to Hotchkin and Riveroll, Jr. (2005), individual A. marmorata are fast-moving and extremely wary, whereas individual A. tesselata are slower, deliberate, and more methodical in their actions. According to Price et al. (1993), these behavioral differences could imply that predators preferentially select A. tesselata as prey and also explain the lower numbers collected in our study. Lower annual numbers of A. tesselata also have been noted repeatedly by JDJ and students at Indio Mountains Research Station for 16 years (pers. obser.). Hotchkin and Riveroll (2005) found that A. marmorata on the research station generally have a greater average flight distances than do A. tesselata, but differences were not statistically significant. However, Pilz (1983) found A. marmorata to be the single most common item in the diet of nestling Swainson's hawks in south-central New Mexico (155 individuals; 23 and 32% of the total diet in 2 years); only four A. tesselata, comprising 1% of the diet each year, were observed during that study. It is doubtful that Swainson's hawks are selective as to which species of Aspidoscelis they prefer and more likely feed on whichever lizard they can catch most often. Their findings oppose the notion that the slower and less wary A. tesselata should be captured most often. It is possible, however, that A. marmorata are present in a much higher percentage at the site in New Mexico, which would account for a greater potential for predation. Milstead (1965) suggested several other factors, in addition to pressures of predation, that presumably decreased size of populations of lizards and reduced the potential for predation. These included susceptibility to disease, inability to withstand severe weather conditions, and effects of parasitism, among others. The assessment of endoparasites (nematodes) in the same specimens used in our study revealed that A. tesselata contained almost 50% higher loads of parasites than did A. marmorata (Mata-Silva et al., 2008), which could affect the overall disparity in population size between the two species.

Although our results indicate that A. marmorata and A. tesselata have similar body proportions and dietary preferences, they do exhibit differences to varying degrees in proportions of prey, and opportunistic feeding behavior, in addition to reproductive strategies and differential resistance to parasites, could potentially lead to some sort of resource partitioning allowing them to coexist on Indio Mountains Research Station, at least at the present time. More investigations into the natural histories of A. marmorata and A. tesselata are needed to determine the holistic factors necessary for allowing them to live together successfully.

This project was made possible through grant funding by the National Science Foundation facilities development (FSML) on Indio Mountains Research Station. We thank P. Lenhart, H. Riveroll, Jr., J. Hobert, M. Vargas, V. Renteria, S. Kumar, and other colleagues for assistance with fieldwork. D. LeMone, C. S. Lieb, and W. P. Mackay provided valuable input for this study. We also thank H. L. Taylor and an anonymous reviewer for comments that greatly improved the manuscript.


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Submitted 10 June 2011. Accepted 23 March 2013. Associate Editor was Geoffrey C. Carpenter.

Vicente Mata-Silva, * Jerry D. Johnson, and Aurelio Ramirez-Bautista

Department of Biological Sciences, University of Texas at El Paso, El Paso, TX 79968 (VMS, JDJ) Laboratorio de Ecologia de Poblaciones, Centro de Investigaciones Biologicas, Universidad Autonoma del Estado de Hidalgo, Plaza Juarez, A.P. 1-69, C.P. 42001, Pachuca, Hidalgo, Mexico (ARB)

* Correspondent:
TABLE 1--Mean ([+ or -] SE), with range in parentheses, of morphological
characteristics of adult Aspidoscelis marmorata and Aspidoscelis
tesselata from Indio Mountain Research Station, Hudspeth County, Texas.

                                         A. marmorata

                        Males              Females
Characteristics         (n = 71)           (n = 11)           Z

Body mass (g)           17.5 [+ or -] 0.5  14.9 [+ or -] 0.6  0.42
                        (7.5-24.6)         (10.2-17.2)
Snout-vent length (mm)  83.5 [+ or -] 0.8  80.9 [+ or -] 1.0  1.55
                        (67-94)            (75-87)
Head length (mm)        22.0 [+ or -] 0.2  20.2 [+ or -] 0.3  0.19
                        (18.0-25.0)        (18.7-22.1)
Head width (mm)         13.0 [+ or -] 0.1  11.5 [+ or -] 0.2  0.14
                        (9.5-15.8)         (10.0-12.9)
Head height (mm)        10.4 [+ or -] 0.1  9.0 [+ or -] 0.1   0.21
                        (7.4-12.4)         (8.1-10.0)

                        A. marmorata       A. tesselata

                        females            females
Characteristics         (n = 11)           (n = 24)           Z

Body mass (g)           14.9 [+ or -] 0.6  17.0 [+ or -] 0.9  1.43
                        (10.2-17.2)        (8.4-25.4)
Snout-vent length (mm)  80.9 [+ or -] 1.0  83.2 [+ or -] 1.5  1.29
                        (75-87)            (66-94)
Head length (mm)        20.2 [+ or -] 0.3  20.9 [+ or -] 0.3  1.52
                        (18.7-22.1)        (17.2-23.8)
Head width (mm)         11.5 [+ or -] 0.2  11.5 [+ or -] 0.1  0.05
                        (10.0-12.9)        (9.9-13.3)
Head height (mm)        9.0 [+ or -] 0.1   9.5 [+ or -] 0.1   1.33
                        (8.1-10.0)         (7.9-10.9)

                        A. marmorata       A. tesselata

                        males              females
Characteristics         (n = 71)           (n = 24)           Z

Body mass (g)           17.5 [+ or -] 0.5  17.0 [+ or -] 0.9  0.43
                        (7.5-24.6)         (8.4-25.4)
Snout-vent length (mm)  83.5 [+ or -] 0.8  83.2 [+ or -] 1.5  0.01
                        (67-94)            (66-94)
Head length (mm)        22.0 [+ or -] 0.2  20.9 [+ or -] 0.3  2.56 *
                        (18.0-25.0)        (17.2-23.8)
Head width (mm)         13.0 [+ or -] 0.1  11.5 [+ or -] 0.1  4.07 *
                        (9.5-15.8)         (9.9-13.3)
Head height (mm)        10.4 [+ or -] 0.1  9.5 [+ or -] 0.1   3.01 *
                        (7.4-12.4)         (7.9-10.9)

(*) Significantly different at P < 0.05 (Mann-Whitney U-test).

TABLE 2--composition of the diet of Aspidoscelis marmorata and
Aspidoscelis tesselata from Indio Mountains Research Station,
Hudspeth County, Texas.

                                 A. marmorata


Taxon                Number (%)         Volume (a) (%)

Chilopoda           1       (0.04)     89.02        (0.30)
Pseudoscorpiones    1       (0.04)     0.67         (0.00)
Solpugida           1       (0.04)     18.23        (0.06)
Araneae             17      (0.81)     3,470.21     (11.91)
Thysanura           1       (0.04)     2.20         (0.00)
Odonata             1       (0.04)     454.02       (1.55)
Orthoptera          16      (0.76)     5,232.62     (17.96)
Isoptera            1,959   (93.46)    4,837.18     (16.60)
Homoptera (b)       20      (0.95)     11,001.06    (37.76)
Hemiptera           36      (1.71)     1,478.92     (5.07)
Coleoptera          21      (1.00)     2,097.45     (7.19)
Lepidoptera         11      (0.52)     353.70       (1.21)
Hymenoptera         10      (0.47)     84.47        (0.28)
Diptera             1       (0.04)     12.76        (90.04)
Total               2,096   (100.00)   29,132.56    (100.00)

                             A. marmorata


Taxon               Number (%)           Volume (%)

Chilopoda          0      (0.00)     0            (0.00)
Pseudoscorpiones   1      (0.55)     5.75         (0.05)
Solpugida          0      (0.00)     0            (0.00)
Araneae            4      (2.23)     5,817.45     (54.08)
Thysanura          0      (0.00)     0            (0.00)
Odonata            0      (0.00)     0            (0.00)
Orthoptera         2      (1.11)     101          (0.93)
Isoptera           150    (83.79)    385.94       (3.58)
Homoptera (b)      2      (1.11)     1105.68      (10.27)
Hemiptera          7      (3.91)     265.78       (2.47)
Coleoptera         9      (5.02)     149.75       (1.39)
Lepidoptera        0      (0.00)     0            (0.00)
Hymenoptera        4      (2.23)     2,925.58     (27.19)
Diptera            0      (0.00)     0            (0.00)
Total              179    (100.00)   10,756.96    (100.00)

                              A. tesselata


Taxon                  Number (%)         Volume (%)

Chilopoda            1       (0.15)    48.22        (0.48)
Pseudoscorpiones     0       (0.00)    0.00         (0.00)
Solpugida            0       (0.00)    0.00         (0.00)
Araneae              5       (0.77)    1,665.93     (16.60)
Thysanura            0       (0.00)    0.00         (0.00)
Odonata              0       (0.00)             0   (0.00)
Orthoptera           10      (1.55)    2,988.34     (29.78)
Isoptera             608     (94.55)   1,628.69     (16.23)
Homoptera (b)        7       (1.08)    2,984.19     (29.74)
Hemiptera            0       (0.00)    0.00         (0.00)
Coleoptera           8       (1.24)    689.49       (6.87)
Lepidoptera          3       (0.46)    26.68        (0.26)
Hymenoptera          1       (0.15)    1.48         (0.01)
Diptera              0       (0.00)    0.00         (0.00)
Total                643     (100.00)  10,033.04    (100.00)

(a) In cubic millimeters.

(b) Includes adults and molts.

TABLE 3--Number (percentage in parentheses) of Aspidoscelis
marmorata and Aspidoscelis tesselata (from Indio Mountains
Research Station, Hudspeth County, Texas) containing each
taxon of prey.

                               A. marmorata                A. tesselata
                      Males       Females     Both         females
Taxon                             (%)         sexes (%)

Chilopoda             1 (2)       0 (0)       1 (1)        1 (5)
Pseudoscorpiones      1 (2)       1 (11)      2 (3)        0 (0)
Solpugida             1 (2)       0 (0)       1 (1)        0 (0)
Araneae               12 (20)     4 (44)      16 (23)      5 (24)
Thysanura             1 (2)       0 (0)       1 (1)        0 (0)
Odonata               1 (2)       0 (0)       1 (1)        0 (0)
Orthoptera            16 (27)     3 (33)      19 (28)      9 (43)
Isoptera              39 (65)     7 (78)      46 (67)      15 (71)
Homoptera             20 (33)     2 (22)      22 (32)      7 (33)
Hemiptera             8 (13)      1 (11)      9 (13)       0 (0)
Coleoptera            18 (30)     5 (56)      23 (33)      5 (24)
Lepidoptera           9 (15)      0 (0)       9 (13)       1 (5)
Hymenoptera           6 (10)      1 (11)      7 (10)       1 (5)
Diptera               1 (2)       0 (0)       1 (1)        0 (0)
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Article Details
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Author:Mata-Silva, Vicente; Johnson, Jerry D.; Ramirez-Bautista, Aurelio
Publication:Southwestern Naturalist
Article Type:Report
Geographic Code:1U7TX
Date:Jun 1, 2013
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