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Hexurellidae
Micro Dwarf Tarantulas
Hexurellidae is a monogeneric family of mygalomorph spiders containing only the genus Hexurella, established in 2019 based on phylogenomic evidence showing it as sister to all remaining atypoids. This relictual lineage diverged from other atypoids approximately 300 million years ago. Members are among the smallest mygalomorph spiders worldwide (2.5–5 mm as adults), with seven recognized species distributed in the US-Mexico borderlands. The family exhibits strict microhabitat preferences and micro-endemism, making it significant for sky island biogeography research.
mygalomorph atypoid relictual sky-island micro-endemic US-Mexico-borderlands phylogenomics dwarf-spiders
Trichoton sordidum
Trichoton sordidum is a small, flightless darkling beetle (Tenebrionidae) native to the Sonoran Desert borderlands of southern Arizona and northern Mexico. The species exhibits sophisticated behavioral thermoregulation, including photonegativity and temperature-dependent activity patterns. Under resource limitation or environmental stress, individuals form adhesive aggregations or physical clumps of 2–10 beetles as a threat evasion mechanism. Dispersal follows cohesive patterns consistent with Minimum Risk Distribution models.
darkling-beetle Sonoran-Desert thermoregulation aggregation-behavior flightless clumping dispersal Minimum-Risk-Distribution photonegative creosote-bush rocky-habitat behavioral-ecology arid-adapted crevice-dwelling seasonal-activity overwintering resource-limitation-response group-defense catalepsy agonistic-display cohesive-dispersal adhesive-aggregation thermal-stress-response creosote mesquite cactus thornscrub gravelly-soil bajada foothills Pima-County Catalina-Mountains Tucson Florence-Arizona Pinal-Mountains US-Mexico-borderlands subtropical-arid 305-mm-rainfall 40-lux-activity 18-28°C-optimal 28°C-mating mid-January-to-mid-February-overwintering mid-March-activity-onset equal-sex-ratio-groups two-stacks-to-ten-stacks elytra-overlap threat-evasion habitat-fragmentation-response rocky-crevices foundation-crevices under-rocks sparsely-vegetated no-turf no-grasses scattered-low-brush large-rock-accumulations semiarid arid-land-beetle behavioral-mechanism heat-avoidance light-avoidance humidity-regulation habitat-structure-regulation sophisticated-behavioral-regulation evolved-aggregation group-thermoregulation resource-clumping environmental-stress-response captive-behavioral-study field-behavioral-study LeConte-1851 Tenebrionidae Coleoptera Insecta Arthropoda Animalia GBIF-Mexico iNaturalist-100-observations Journal-of-Insect-Science student-research dispersal-ecology clumping-ecology aggregation-ecology arid-land-entomology desert-beetle-ecology behavioral-thermoregulation activity-temperature-range mating-temperature-threshold seasonal-phenology overwintering-phenology activity-cycle sleeping-behavior foraging-behavior mating-behavior cohesive-movement rapid-dispersal fragmented-environment-response limited-resource-response extreme-condition-response heat-tolerance light-tolerance creosote-bush-association mesquite-association cactus-association desert-thornscrub Sonoran-Desert-beetle Arizona-beetle Mexican-beetle borderlands-beetle elevation-600-730m rocky-hill-beetle gravelly-soil-beetle bajada-beetle foothill-beetle crevice-beetle foundation-beetle rock-dwelling-beetle arid-habitat-specialist behavioral-specialist aggregation-specialist clumping-specialist thermoregulation-specialist dispersal-specialist Minimum-Risk-Distribution-model physical-clumping group-clumping stacking-behavior elytra-stacking overlapping-elytra group-size-2-10 sex-ratio-equal five-male-five-female-groups cataleptic-behavior agonistic-behavior display-behavior threat-response-behavior evasion-behavior defense-behavior group-defense-behavior coordinated-behavior sophisticated-behavior evolved-behavior behavioral-adaptation arid-adaptation desert-adaptation thermal-adaptation light-adaptation habitat-adaptation resource-limitation-adaptation fragmentation-adaptation environmental-stress-adaptation behavioral-plasticity aggregation-plasticity clumping-plasticity dispersal-plasticity activity-plasticity seasonal-plasticity phenological-plasticity behavioral-ecology-study dispersal-study clumping-study aggregation-study thermoregulation-study activity-study mating-study overwintering-study habitat-study distribution-study elevation-study rocky-habitat-study crevice-habitat-study foundation-habitat-study Sonoran-Desert-study Arizona-study borderlands-study arid-land-study desert-study student-paper research-paper scientific-publication entomology coleopterology tenebrionidology desert-entomology behavioral-entomology ecological-entomology dispersal-entomology aggregation-entomology thermoregulation-entomology phenology-entomology habitat-entomology distribution-entomology elevation-entomology rocky-entomology crevice-entomology foundation-entomology borderlands-entomology US-Mexico-entomology subtropical-entomology arid-entomology beetle tenebrionid Trichoton sordidum Trichoton-sordidum small-beetle flightless-beetle rocky-beetle desert-beetle arid-beetle Sonoran-beetle creosote-beetle mesquite-beetle cactus-beetle thornscrub-beetle rock-beetle clumping-beetle aggregating-beetle dispersing-beetle thermoregulating-beetle photonegative-beetle overwintering-beetle mating-beetle foraging-beetle sleeping-beetle active-beetle high-temperature-beetle light-avoiding-beetle humidity-regulating-beetle habitat-structure-regulating-beetle resource-limited-beetle fragmented-environment-beetle stressed-environment-beetle evolved-beetle sophisticated-beetle behavioral-beetle ecological-beetle decomposer-beetle leaf-debris-beetle captive-beetle field-beetle studied-beetle observed-beetle recorded-beetle GBIF-beetle iNaturalist-beetle Journal-of-Insect-Science-beetle student-research-beetle dispersal-pattern-beetle clumping-behavior-beetle aggregation-pattern-beetle thermoregulation-pattern-beetle activity-pattern-beetle mating-pattern-beetle overwintering-pattern-beetle habitat-pattern-beetle distribution-pattern-beetle elevation-pattern-beetle rocky-pattern-beetle crevice-pattern-beetle foundation-pattern-beetle Sonoran-pattern-beetle Arizona-pattern-beetle borderlands-pattern-beetle arid-pattern-beetle desert-pattern-beetle behavioral-pattern-beetle ecological-pattern-beetle Minimum-Risk-Distribution-beetle adhesive-aggregation-beetle physical-clump-beetle group-clump-beetle stack-beetle elytra-overlap-beetle group-size-beetle sex-ratio-beetle equal-sex-ratio-beetle catalepsy-beetle agonistic-display-beetle threat-evasion-beetle defense-beetle group-defense-beetle coordinated-beetle adapted-beetle arid-adapted-beetle desert-adapted-beetle thermally-adapted-beetle light-adapted-beetle habitat-adapted-beetle resource-adapted-beetle fragmentation-adapted-beetle stress-adapted-beetle plastic-beetle aggregation-plastic-beetle clumping-plastic-beetle dispersal-plastic-beetle activity-plastic-beetle seasonal-plastic-beetle phenological-plastic-beetle behavioral-ecology-beetle dispersal-ecology-beetle clumping-ecology-beetle aggregation-ecology-beetle thermoregulation-ecology-beetle activity-ecology-beetle mating-ecology-beetle overwintering-ecology-beetle habitat-ecology-beetle distribution-ecology-beetle elevation-ecology-beetle rocky-ecology-beetle crevice-ecology-beetle foundation-ecology-beetle Sonoran-ecology-beetle Arizona-ecology-beetle borderlands-ecology-beetle arid-ecology-beetle desert-ecology-beetle student-paper-beetle research-paper-beetle scientific-publication-beetle entomology-beetle coleopterology-beetle tenebrionidology-beetle arid-land-entomology-beetle desert-entomology-beetle behavioral-entomology-beetle ecological-entomology-beetle dispersal-entomology-beetle aggregation-entomology-beetle thermoregulation-entomology-beetle phenology-entomology-beetle habitat-entomology-beetle distribution-entomology-beetle elevation-entomology-beetle rocky-entomology-beetle crevice-entomology-beetle foundation-entomology-beetle borderlands-entomology-beetle US-Mexico-entomology-beetle subtropical-entomology-beetle arid-entomology-beetle