Water and Temperature Relations of Two Hemipteran Members of a Predator-Prey Complex

Certain aspects of temperature and water relations were investigated in individuals of two hemipteran species that live in arid habitats. Thermal tolerance, measured as critical thermal maximum (CTM), was considerably higher in Geocoris punctipes (Say) (Hemiptera: Lygaeidae) (CTM = 47.8) than in Lygus hesperus (Knight) (Hemiptera: Miridae) (CTM = 42.4). L. hesperus had higher resistance to water loss at high temperatures than G. punctipes, whereas both species had rates of water loss that were generally higher than other arthropods that inhabit arid zones. Fecal water loss was higher in L. hesperus than it was in G. punctipes (5.5%·day⁻¹ compared with 2.7%·day⁻¹) L. hesperus had a significantly lesser amount of cuticular lipid per cm²; $\bar x$ = 33.2 mg·cm⁻² (SD = 8.4) than did G. punctipes; $\bar x$ = 53.4 (SD = 16.2). Older adults had lower rates of water loss than did newly emerged adults (P < 0.001).