Us-mexico-borderlands
Guides
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.
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-beetleSonoran-Desertthermoregulationaggregation-behaviorflightlessclumpingdispersalMinimum-Risk-Distributionphotonegativecreosote-bushrocky-habitatbehavioral-ecologyarid-adaptedcrevice-dwellingseasonal-activityoverwinteringresource-limitation-responsegroup-defensecatalepsyagonistic-displaycohesive-dispersaladhesive-aggregationthermal-stress-responsecreosotemesquitecactusthornscrubgravelly-soilbajadafoothillsPima-CountyCatalina-MountainsTucsonFlorence-ArizonaPinal-MountainsUS-Mexico-borderlandssubtropical-arid305-mm-rainfall40-lux-activity18-28°C-optimal28°C-matingmid-January-to-mid-February-overwinteringmid-March-activity-onsetequal-sex-ratio-groupstwo-stacks-to-ten-stackselytra-overlapthreat-evasionhabitat-fragmentation-responserocky-crevicesfoundation-crevicesunder-rockssparsely-vegetatedno-turfno-grassesscattered-low-brushlarge-rock-accumulationssemiaridarid-land-beetlebehavioral-mechanismheat-avoidancelight-avoidancehumidity-regulationhabitat-structure-regulationsophisticated-behavioral-regulationevolved-aggregationgroup-thermoregulationresource-clumpingenvironmental-stress-responsecaptive-behavioral-studyfield-behavioral-studyLeConte-1851TenebrionidaeColeopteraInsectaArthropodaAnimaliaGBIF-MexicoiNaturalist-100-observationsJournal-of-Insect-Sciencestudent-researchdispersal-ecologyclumping-ecologyaggregation-ecologyarid-land-entomologydesert-beetle-ecologybehavioral-thermoregulationactivity-temperature-rangemating-temperature-thresholdseasonal-phenologyoverwintering-phenologyactivity-cyclesleeping-behaviorforaging-behaviormating-behaviorcohesive-movementrapid-dispersalfragmented-environment-responselimited-resource-responseextreme-condition-responseheat-tolerancelight-tolerancecreosote-bush-associationmesquite-associationcactus-associationdesert-thornscrubSonoran-Desert-beetleArizona-beetleMexican-beetleborderlands-beetleelevation-600-730mrocky-hill-beetlegravelly-soil-beetlebajada-beetlefoothill-beetlecrevice-beetlefoundation-beetlerock-dwelling-beetlearid-habitat-specialistbehavioral-specialistaggregation-specialistclumping-specialistthermoregulation-specialistdispersal-specialistMinimum-Risk-Distribution-modelphysical-clumpinggroup-clumpingstacking-behaviorelytra-stackingoverlapping-elytragroup-size-2-10sex-ratio-equalfive-male-five-female-groupscataleptic-behavioragonistic-behaviordisplay-behaviorthreat-response-behaviorevasion-behaviordefense-behaviorgroup-defense-behaviorcoordinated-behaviorsophisticated-behaviorevolved-behaviorbehavioral-adaptationarid-adaptationdesert-adaptationthermal-adaptationlight-adaptationhabitat-adaptationresource-limitation-adaptationfragmentation-adaptationenvironmental-stress-adaptationbehavioral-plasticityaggregation-plasticityclumping-plasticitydispersal-plasticityactivity-plasticityseasonal-plasticityphenological-plasticitybehavioral-ecology-studydispersal-studyclumping-studyaggregation-studythermoregulation-studyactivity-studymating-studyoverwintering-studyhabitat-studydistribution-studyelevation-studyrocky-habitat-studycrevice-habitat-studyfoundation-habitat-studySonoran-Desert-studyArizona-studyborderlands-studyarid-land-studydesert-studystudent-paperresearch-paperscientific-publicationentomologycoleopterologytenebrionidologydesert-entomologybehavioral-entomologyecological-entomologydispersal-entomologyaggregation-entomologythermoregulation-entomologyphenology-entomologyhabitat-entomologydistribution-entomologyelevation-entomologyrocky-entomologycrevice-entomologyfoundation-entomologyborderlands-entomologyUS-Mexico-entomologysubtropical-entomologyarid-entomologybeetletenebrionidTrichotonsordidumTrichoton-sordidumsmall-beetleflightless-beetlerocky-beetledesert-beetlearid-beetleSonoran-beetlecreosote-beetlemesquite-beetlecactus-beetlethornscrub-beetlerock-beetleclumping-beetleaggregating-beetledispersing-beetlethermoregulating-beetlephotonegative-beetleoverwintering-beetlemating-beetleforaging-beetlesleeping-beetleactive-beetlehigh-temperature-beetlelight-avoiding-beetlehumidity-regulating-beetlehabitat-structure-regulating-beetleresource-limited-beetlefragmented-environment-beetlestressed-environment-beetleevolved-beetlesophisticated-beetlebehavioral-beetleecological-beetledecomposer-beetleleaf-debris-beetlecaptive-beetlefield-beetlestudied-beetleobserved-beetlerecorded-beetleGBIF-beetleiNaturalist-beetleJournal-of-Insect-Science-beetlestudent-research-beetledispersal-pattern-beetleclumping-behavior-beetleaggregation-pattern-beetlethermoregulation-pattern-beetleactivity-pattern-beetlemating-pattern-beetleoverwintering-pattern-beetlehabitat-pattern-beetledistribution-pattern-beetleelevation-pattern-beetlerocky-pattern-beetlecrevice-pattern-beetlefoundation-pattern-beetleSonoran-pattern-beetleArizona-pattern-beetleborderlands-pattern-beetlearid-pattern-beetledesert-pattern-beetlebehavioral-pattern-beetleecological-pattern-beetleMinimum-Risk-Distribution-beetleadhesive-aggregation-beetlephysical-clump-beetlegroup-clump-beetlestack-beetleelytra-overlap-beetlegroup-size-beetlesex-ratio-beetleequal-sex-ratio-beetlecatalepsy-beetleagonistic-display-beetlethreat-evasion-beetledefense-beetlegroup-defense-beetlecoordinated-beetleadapted-beetlearid-adapted-beetledesert-adapted-beetlethermally-adapted-beetlelight-adapted-beetlehabitat-adapted-beetleresource-adapted-beetlefragmentation-adapted-beetlestress-adapted-beetleplastic-beetleaggregation-plastic-beetleclumping-plastic-beetledispersal-plastic-beetleactivity-plastic-beetleseasonal-plastic-beetlephenological-plastic-beetlebehavioral-ecology-beetledispersal-ecology-beetleclumping-ecology-beetleaggregation-ecology-beetlethermoregulation-ecology-beetleactivity-ecology-beetlemating-ecology-beetleoverwintering-ecology-beetlehabitat-ecology-beetledistribution-ecology-beetleelevation-ecology-beetlerocky-ecology-beetlecrevice-ecology-beetlefoundation-ecology-beetleSonoran-ecology-beetleArizona-ecology-beetleborderlands-ecology-beetlearid-ecology-beetledesert-ecology-beetlestudent-paper-beetleresearch-paper-beetlescientific-publication-beetleentomology-beetlecoleopterology-beetletenebrionidology-beetlearid-land-entomology-beetledesert-entomology-beetlebehavioral-entomology-beetleecological-entomology-beetledispersal-entomology-beetleaggregation-entomology-beetlethermoregulation-entomology-beetlephenology-entomology-beetlehabitat-entomology-beetledistribution-entomology-beetleelevation-entomology-beetlerocky-entomology-beetlecrevice-entomology-beetlefoundation-entomology-beetleborderlands-entomology-beetleUS-Mexico-entomology-beetlesubtropical-entomology-beetlearid-entomology-beetle