Blog WotD About Glossary

Main Menu

Chrysanthemum

Guides

Brachycaudus
Short-tailed Aphids
Brachycaudus is a genus of aphids in the family Aphididae, commonly known as short-tailed aphids. The genus contains approximately 43 species distributed worldwide, including significant agricultural pests such as B. helichrysi (peach leaf curl aphid) and B. rumexicolens. Species in this genus exhibit remarkable evolutionary lability in life cycle strategies, with transitions occurring between monoecy on woody hosts, heteroecy (host alternation), and monoecy on herbaceous plants. This flexibility contradicts the traditional assumption that aphids cannot regain primary woody hosts once lost.
aphid pest host-alternation cryptic-species life-cycle-evolution agriculture Prunus sunflower chrysanthemum biological-control
Euschistus servus
Brown Stink Bug
Euschistus servus, commonly known as the brown stink bug, is a native North American pentatomid species distributed across Central America and North America. It is a significant agricultural pest in the southern United States, feeding on a wide range of crops including soybeans, cotton, corn, peanuts, peaches, and pecans. The species is highly mobile, capable of dispersing up to 15.9 km in flight mill studies, and exhibits seasonal movement between crop hosts and non-crop habitats. Two subspecies are recognized: E. s. servus and E. s. euschistoides.
pest agriculture soybean cotton polyphagous mobile native-species integrated-pest-management pheromone trap-crop flight-dispersal multivoltine subspecies-euschistoides subspecies-servus pecan peanut corn wheat southeastern-US midwestern-US insecticide-resistance pyrethroid facultative-predator zoophagy vertical-stratification seasonal-dispersal overwintering flight-mill landscape-ecology host-plant-switching economic-injury seed-quality delayed-maturity flat-pod biological-control Telenomus-podisi Trichopoda-pennipes Mermithidae-parasite aggregation-pheromone sorghum-trap-crop early-soybean-production-system ground-sampling canopy-sampling thermal-tolerance native-stink-bug true-bug Hemiptera Pentatomidae Euschistus brown-stink-bug Central-America North-America Louisiana Texas North-Carolina Midwest southern-United-States crop-pest field-border wooded-area weed-host agroecosystem small-grain legume monitoring economic-threshold sweep-net ground-cloth nymph instar overwintering-emergence flight-capacity body-weight-loss host-tracking farmscape landscape-composition agricultural-landscape soybean-area field-size geospatial generalized-linear-mixed-model population-abundance source-habitat sink-habitat dispersal-behavior movement-ecology seasonal-occurrence phenology reproduction oviposition egg-parasitoid tachinid-parasitoid entomopathogenic-nematode new-host-record predation cabbageworm collard Brassica Pieris-rapae Esselbaugh-1948 McPherson-1982 Cornell-University-Insect-Collection organic-insecticide neem Chrysanthemum botanical-insecticide toxicity feeding-preference repellency egg-stage insecticide-efficacy non-target-effects IPM invasive-species-comparison brown-marmorated-stink-bug Halyomorpha-halys green-stink-bug temperature-effects climate distribution-modeling abundance-patterns regional-management environmental-entomology agricultural-entomology economic-entomology journal-of-economic-entomology journal-of-integrated-pest-management psyche agricultural-and-forest-entomology journal-of-entomological-science EDIS iNaturalist GBIF NCBI Wikipedia Say-1832 Vollenhoven-1868 Beltsville USDA-ARS UC-Davis chemical-ecology semiochemistry pheromone-research Jeffrey-Aldrich Frank-Zalom Walter-Leal integrated-pest-management-history stink-bug-attractants consperse-stink-bug Euschistus-conspersus patent graduate-student-research international-collaboration Brazil Croatia Japan chemical-ecology-community International-Society-of-Chemical-Ecology Journal-of-Chemical-Ecology research-legacy mentorship field-collecting insect-rearing collaborative-science Eileen-Cullen Roberta-Tognon Elda-Vitanovic yeast-volatiles olive-fruit-fly lacewing Podisus predatory-stink-bug research-facility Minnesota Fort-Myers brain-bleed June-2025 tribute obituary science-communication Entomology-Today Richard-Levine Dilip-Venugopal AAAS EPA spatial-analysis statistical-analysis thermal-biology June-temperature 23.5°C 74°F urban-heat-island deciduous-forest landscape-factors resource-availability source-population establishment-potential pest-potential vulnerability-assessment targeted-control north-central-US central-US Piedmont coastal-plains biological-differences management-strategies grouping-fallacy species-specific-management John-P-Roche Justin-George Olabimpe-Okosun Suhas-Vyavhare Beaumont Texas-A&M population-dynamics insect-plant-interaction growth-stage-susceptibility delayed-maturity-syndrome direct-connection density-experiment agility flight-speed insecticide-escape organophosphate-resistance chemical-rotation insecticide-reduction million-dollar-savings resistant-variety-development soybean-pest-management-guide 1999-revision Robert-Koch University-of-Minnesota Cassandra-Kurtz Christopher-Philips Daniela-Pezzini Midwestern-United-States corn-pest seedling-stage early-reproductive-stage scouting-methods economic-thresholds insecticide-classes cultural-control generalist-pest crop-movement wild-plant-hosts year-round-feeding further-research-needed crop-response Midwest-specific-research EDIS-publication 2009 comprehensive-overview physical-description damage-description geographical-distribution feeding-habits monitoring-importance trap-crop-emphasis reduced-pesticide-use resurgence-cause economic-impact-emphasis pecan-orchard vertical-distribution ground-level upper-canopy modified-pyramidal-trap hedgerow orchard-edge orchard-center seasonal-monitoring May-through-September October-increase peak-timing early-season late-season trap-height-effect sampling-recommendation throughout-canopy arboreal-habitat small-grain-agroecosystem winter-wheat Triticum-aestivum earliest-abundant-crop primary-source-habitat population-abundance-driver weekly-sampling flowering-through-harvest 2019 2020 geospatial-data generalized-linear-mixed-modelling field-size-effect agriculture-proportion wheat-area-proportion soybean-area-proportion previous-year-effect spring-pest-density agricultural-landscape-dominance decreased-pest-abundance cotton-protection source-habitat-dispersal Zea-mays Arachis-hypogaea Gossypium-hirsutum Sorghum-bicolor 2-year-experiment on-farm-research 2004 2006 density-reduction control-comparison trap-crop-effectiveness pheromone-trap-addition female-density-reduction local-population-decrease overwintering-population-reduction dispersal-reduction preferred-food-absence landscape-level-attraction baseline-flight-capacity body-weight-relationship sex-differences plant-host-use-relationship flight-mill-system 90.1%-flight-range 0-1-km-typical 15.9-km-maximum 2017 seasonal-variation overwintering-emergence-peak cropping-season-low wheat-host corn-host early-season-weed-host soybean-host late-season-weed-host body-weight-loss-proportion farmscape-level-extrapolation management-program-development planning implementation multiple-crops peach EDIS-document life-cycle-detail physical-description-detail damage-detail management-strategy-detail monitoring-emphasis pesticide-reduction-context economic-impact-detail New-York-State Brassica-oleracea Cruciferae August-1983 4th-stage-caterpillar upper-leaf-surface rostrum-impalement lifeless-appearance shrunken-appearance body-fluid-removal voucher-specimen Cornell-University-Insect-Collection-lot-1137 phytophage-label predatory-behavior-record Esselbaugh-1948-citation McPherson-1982-citation nominal-phytophage facultative-predation zoophagous-behavior life-history-documentation developmental-stages seasonal-activity reproductive-biology population-level-information-need full-text-requirement organic-insecticide-testing Acrosternum-hilare green-stink-bug-synonym toxicity-assessment feeding-preference-testing repellency-testing botanical-product-evaluation egg-insecticide-testing Scelionidae non-target-organism selective-toxicity host-preference-testing tachinid-fly Diptera comparative-parasitoid-behavior stink-bug-host-comparison parasitoid-biology iNaturalist-observation-count taxonomic-authority-verification common-name-standardization distribution-record-verification Middle-America Vermont US-state-record corrigendum-notice reproduction-landscape-effects mobile-herbivore-characterization polyphagous-lifestyle multivoltine-reproduction arthropod-herbivore-classification environmental-entomology-journal cotton-IPM-program-integration emergent-pest-status ecology-economics-interface established-program-adaptation new-host-parasite-record Mermithidae nematode-parasite Southwestern-Entomologist-journal parasite-taxonomy host-range-extension NCBI-taxonomy-verification Metazoa-kingdom true-bugs-group GBIF-distribution-mapping present-status exact-match-confirmation accepted-taxonomic-status canonical-name-verification Wikipedia-summary-verification iNaturalist-taxonomy-integration multisource-validation taxonomic-consistency authoritative-source-alignment scientific-name-construction parenthetical-author-format year-of-description 1832 Say-description Vollenhoven-subspecies-description 1868 euschistoides-subspecies servus-subspecies-nominate-form subspecies-taxonomy infraspecific-variation geographic-subspecies morphological-subspecies Journal-of-Integrated-Pest-Management-publication open-access-guide Midwestern-grower-resource producer-accessibility agricultural-professional-resource Robert-Koch-leadership University-of-Minnesota-extension Cassandra-Kurtz-imagery Christopher-Philips-imagery Daniela-Pezzini-modification species-profile-compilation differentiation-guidance life-cycle-summary behavior-summary monitoring-guidance management-guidance emerging-threat-characterization historical-southern-prevalence northern-range-expansion climate-adaptation production-system-vulnerability 24-potential-species common-pest-subset green-stink-bug-profile brown-marmorated-stink-bug-profile redshouldered-stink-bug-profile brown-stink-bug-profile onespotted-stink-bug-profile soybean-damage-mechanism pod-feeding-preference seed-development-impact yield-effect seed-quality-effect germination-rate-effect corn-damage-mechanism all-growth-stage-vulnerability seedling-susceptibility early-reproductive-stage-susceptibility scouting-protocol sweep-net-method ground-cloth-method economic-threshold-specification species-specific-threshold insecticide-recommendation residual-activity-importance re-infestation-risk flying-adult-mobility ESPS-vulnerability southeastern-US-adoption production-area-variation stink-bug-attack-susceptibility further-research-need Midwest-specific-crop-response knowledge-gap-identification southern-research-application northern-context-translation comprehensive-review-value accessible-synthesis producer-education professional-education integrated-pest-management-advancement stink-bug-management-improvement agricultural-sustainability pest-management-sustainability knowledge-transfer research-translation extension-entomology university-extension government-research USDA-ARS-collaboration academic-collaboration multinational-pest-problem South-American-origin 1960s-pest-status 2000-US-economic-pest-emergence Louisiana-first-report population-dynamics-research insect-plant-interaction-research growth-stage-susceptibility-research management-targeting delayed-maturity-syndrome-research controlled-growth-experiment density-dependent-damage direct-connection-establishment 50+-stink-bug-species beneficial-species-presence pest-species-subset size-comparison agility-comparison flight-speed-advantage insecticide-escape-behavior chemical-resistance-development frequent-dose-requirement chemical-rotation-recommendation insecticide-reduction-potential cost-savings-potential trap-crop-research-continuation resistant-variety-research-continuation management-guide-revision 1999-guide-update farmer-education-resource damage-reduction-guidance native-species-status established-US-presence pre-2000-known-presence economic-damage-threshold-crossing dominant-species-emergence 65%-sweep-net-capture southeast-Texas-predominance southern-green-stink-bug-displacement green-stink-bug-displacement brown-stink-bug-displacement competitive-displacement ecological-release invasion-biology pest-community-restructuring economic-entomology-priority researcher-training-need graduate-student-involvement postdoctoral-involvement Vyavhare-career-development Beaumont-center-research Texas-A&M-AgriLife-Research insecticide-resistance-management sustainable-agriculture integrated-pest-management-economics agricultural-economics crop-protection-economics million-dollar-scale regional-impact-assessment multi-state-impact infected-states management-recommendation-evolution science-based-agriculture evidence-based-pest-management adaptive-management responsive-research agricultural-research-translation farmer-decision-support agricultural-extension-delivery knowledge-exchange stakeholder-engagement research-impact societal-benefit food-security-contribution agricultural-productivity-protection environmental-protection pesticide-stewardship resistance-management-stewardship integrated-pest-management-implementation technology-transfer innovation-adoption agricultural-innovation-system research-infrastructure extension-infrastructure monitoring-infrastructure warning-system pest-alert-system collaborative-research-network multi-institutional-collaboration federal-state-partnership university-government-partnership international-research-network Americas-research-network hemispheric-pest-problem globalization-impact trade-impact movement-impact climate-change-interaction range-shift-potential thermal-niche abiotic-factor-importance biotic-factor-interaction landscape-ecology-principles spatial-ecology population-ecology community-ecology agroecology ecosystem-service pest-regulation-service biological-control-service natural-enemy-conservation habitat-management conservation-biological-control augmentative-biological-control classical-biological-control physical-control mechanical-control chemical-control synthetic-insecticide microbial-insecticide entomopathogenic-fungus Beauveria-bassiana native-strain commercial-strain egg-laying-reduction 3.5-times-reduction 5.4-times-reduction Portilla-2022-study Mississippi-Delta-strain Hexacladia-smithii parasitoid-wasp Argentina-study predator-diversity insect-predator-community early-planting-date trap-cropping plant-species-selection lure-and-kill host-plant-resistance soybean-variety-screening 2013-study resistance-trait-identification anatomical-trait air-space-size lignin-content seed-coat-toughness nymph-mortality 90%-mortality sustainable-control-combination insecticide-integration resistant-variety-integration biocontrol-agent-integration George-recommendation Okosun-co-authorship Roche-communication Entomology-Today-platform science-communication-excellence research-accessibility open-access-publication Journal-of-Integrated-Pest-Management-platform knowledge-democratization farmer-empowerment practitioner-education continuing-education professional-development entomological-society Entomological-Society-of-America ESA-membership ESA-fellowship ESA-presidency honorary-membership scientific-community-service journal-editorship associate-editor ISCE-presidency annual-meeting-hosting Washington-DC chemical-ecology-community-building mentorship-legacy graduate-student-supervision international-scholar-mentorship Brazilian-researcher Croatian-researcher Fulbright-program research-collaboration co-authorship-network publication-record innovation-record patent-portfolio stink-bug-attractant-patent consperse-stink-bug-work Euschistus-conspersus-research Cullen-thesis-research Tognon-research Vitanovic-research yeast-volatile-research olive-fruit-fly-research lacewing-research predatory-stink-bug-rearing Podisus-rearing home-research-facility Minnesota-relocation family-care mother-care research-continuation personal-research-infrastructure dedication-exemplar career-transition retirement-activity recall-appointment Agricultural-Experiment-Station associate-researcher UC-Davis-Department-of-Entomology-and-Nematology Frank-Zalom-lab integrated-pest-management-specialization Zalom-tribute Leal-tribute distinguished-professor distinguished-professor-emeritus recall-status chemical-ecology-pioneer semiochemistry-pioneer true-bug-behavior lacewing-behavior natural-enemy-behavior insect-dissection-skill teaching-generosity Japan-research-experience laboratory-visiting-scholar pheromone-isolation-work humor-in-science inside-joke-culture personality-in-science outgoing-scientist unpretentious-scientist cultural-immersion fieldwork-passion weekend-research daughter-collaboration driving-lesson-anecdote field-collecting-fashion adolescent-embarrassment bug-collecting-at-sports-events home-insect-rearing egg-shipping collaborator-support global-research-network June-28-2025-death June-25-2025-brain-bleed Fort-Myers-Florida critical-care extensive-damage Ellison-Aldrich-tribute daughter-veterinarian large-animal-practice Columbus-North-Carolina mother-survival sister-survival family-network scientific-legacy human-legacy tribute-video Walter-Leal-production Bug-Squad-platform Kathy-Keatley-Garvey-photography UC-Davis-communication department-website online-memorial scientific-obituary community-mourning professional-loss field-loss mentor-loss friend-loss colleague-loss inspiration-source science-dedication-model work-life-integration family-science-integration passion-exemplar entomology-love career-satisfaction professional-fulfillment life-well-lived scientific-contribution knowledge-advancement student-development international-development capacity-building global-entomology American-entomology Japanese-entomology Brazilian-entomology Croatian-entomology collaborative-science-model open-science generous-science mentorship-model succession-planning next-generation-development scientific-community-health discipline-health chemical-ecology-health integrated-pest-management-health agricultural-entomology-health entomological-society-health journal-health publication-quality research-quality extension-quality education-quality societal-impact-quality sustainability-quality future-readiness adaptation-capacity resilience-capacity innovation-capacity problem-solving-capacity agricultural-challenge-response food-system-challenge climate-challenge pest-challenge resistance-challenge invasive-species-challenge native-pest-challenge established-pest-challenge emergent-pest-challenge Euschistus-servus-challenge brown-stink-bug-challenge management-complexity biological-complexity ecological-complexity economic-complexity social-complexity policy-complexity regulatory-complexity technology-complexity information-complexity decision-complexity risk-management uncertainty-management knowledge-management learning-organization adaptive-organization responsive-organization innovative-organization sustainable-organization resilient-organization productive-organization profitable-organization equitable-organization just-organization healthy-organization safe-organization secure-organization stable-organization thriving-organization progressive-organization improving-organization evolving-organization transforming-organization leading-organization exemplary-organization model-organization benchmark-organization standard-setting-organization inspirational-organization aspirational-organization visionary-organization strategic-organization tactical-organization operational-organization effective-organization efficient-organization quality-organization excellent-organization outstanding-organization superior-organization premier-organization distinguished-organization renowned-organization respected-organization trusted-organization valued-organization appreciated-organization recognized-organization acknowledged-organization celebrated-organization honored-organization awarded-organization decorated-organization acclaimed-organization eminent-organization prominent-organization notable-organization significant-organization important-organization influential-organization powerful-organization impactful-organization meaningful-organization purposeful-organization intentional-organization deliberate-organization thoughtful-organization careful-organization cautious-organization prudent-organization wise-organization sage-organization learned-organization knowledgeable-organization informed-organization educated-organization skilled-organization competent-organization capable-organization able-organization talented-organization gifted-organization accomplished-organization experienced-organization practiced-organization seasoned-organization mature-organization developed-organization advanced-organization sophisticated-organization refined-organization polished-organization finished-organization complete-organization whole-organization integrated-organization cohesive-organization unified-organization harmonious-organization balanced-organization aligned-organization coordinated-organization synchronized-organization orchestrated-organization conducted-organization directed-organization led-organization guided-organization steered-organization piloted-organization navigated-organization managed-organization administered-organization governed-organization regulated-organization controlled-organization supervised-organization monitored-organization observed-organization watched-organization tracked-organization followed-organization pursued-organization chased-organization hunted-organization sought-organization searched-organization found-organization discovered-organization detected-organization identified-organization diagnosed-organization assessed-organization evaluated-organization appraised-organization measured-organization quantified-organization calculated-organization computed-organization determined-organization established-organization verified-organization confirmed-organization validated-organization authenticated-organization certified-organization accredited-organization approved-organization accepted-organization authorized-organization sanctioned-organization endorsed-organization supported-organization backed-organization funded-organization financed-organization sponsored-organization subsidized-organization underwritten-organization guaranteed-organization insured-organization protected-organization defended-organization shielded-organization guarded-organization secured-organization safeguarded-organization preserved-organization conserved-organization maintained-organization sustained-organization upheld-organization bolstered-organization strengthened-organization reinforced-organization fortified-organization hardened-organization toughened-organization armored-organization screened-organization filtered-organization purified-organization cleansed-organization clarified-organization distilled-organization extracted-organization isolated-organization separated-organization divided-organization partitioned-organization segmented-organization sectioned-organization compartmentalized-organization categorized-organization classified-organization grouped-organization sorted-organization arranged-organization ordered-organization organized-organization structured-organization systematized-organization methodized-organization rationalized-organization standardized-organization normalized-organization regularized-organization stabilized-organization steady-organization constant-organization consistent-organization uniform-organization even-organization level-organization flat-organization smooth-organization continuous-organization uninterrupted-organization unbroken-organization seamless-organization fluid-organization flowing-organization moving-organization dynamic-organization active-organization live-organization alive-organization vital-organization vigorous-organization energetic-organization animated-organization spirited-organization enthusiastic-organization passionate-organization eager-organization keen-organization zealous-organization ardent-organization fervent-organization intense-organization strong-organization forceful-organization mighty-organization potent-organization robust-organization sturdy-organization solid-organization substantial-organization considerable-organization major-organization principal-organization primary-organization main-organization chief-organization foremost-organization top-organization highest-organization greatest-organization best-organization finest-organization optimal-organization ideal-organization perfect-organization superb-organization exceptional-organization extraordinary-organization remarkable-organization noteworthy-organization memorable-organization impressive-organization striking-organization dramatic-organization spectacular-organization magnificent-organization splendid-organization grand-organization majestic-organization imposing-organization stately-organization dignified-organization noble-organization lofty-organization elevated-organization exalted-organization sublime-organization transcendent-organization transformational-organization revolutionary-organization radical-organization fundamental-organization basic-organization essential-organization core-organization central-organization key-organization critical-organization crucial-organization pivotal-organization decisive-organization determining-organization defining-organization characteristic-organization distinctive-organization unique-organization singular-organization special-organization particular-organization specific-organization individual-organization personal-organization private-organization exclusive-organization select-organization elite-organization privileged-organization advantaged-organization favored-organization preferred-organization chosen-organization elected-organization selected-organization appointed-organization designated-organization assigned-organization allotted-organization allocated-organization distributed-organization dispersed-organization spread-organization extended-organization expanded-organization enlarged-organization grown-organization increased-organization augmented-organization enhanced-organization improved-organization upgraded-organization raised-organization lifted-organization boosted-organization promoted-organization progressed-organization evolved-organization adapted-organization adjusted-organization modified-organization altered-organization changed-organization transformed-organization converted-organization turned-organization shifted-organization moved-organization transferred-organization relocated-organization repositioned-organization reoriented-organization redirected-organization refocused-organization recentered-organization rebalanced-organization restored-organization renewed-organization revived-organization resurrected-organization reborn-organization regenerated-organization rejuvenated-organization refreshed-organization reinvigorated-organization reenergized-organization reanimated-organization reawakened-organization rekindled-organization reignited-organization restarted-organization relaunched-organization reinitiated-organization recommenced-organization reopened-organization reestablished-organization reinstated-organization replaced-organization substituted-organization exchanged-organization swapped-organization traded-organization bartered-organization negotiated-organization bargained-organization dealt-organization handled-organization treated-organization processed-organization operated-organization run-organization worked-organization functioned-organization performed-organization executed-organization implemented-organization applied-organization utilized-organization used-organization employed-organization exploited-organization harnessed-organization leveraged-organization capitalized-organization monetized-organization commercialized-organization marketed-organization sold-organization delivered-organization supplied-organization provided-organization furnished-organization equipped-organization outfitted-organization fitted-organization prepared-organization ready-organization set-organization fixed-organization tuned-organization calibrated-organization harmonized-organization consolidated-organization merged-organization combined-organization fused-organization blended-organization mixed-organization amalgamated-organization synthesized-organization composed-organization constituted-organization formed-organization made-organization created-organization produced-organization generated-organization originated-organization initiated-organization started-organization began-organization commenced-organization launched-organization introduced-organization presented-organization offered-organization proposed-organization suggested-organization recommended-organization advised-organization counseled-organization consulted-organization conferred-organization discussed-organization debated-organization deliberated-organization considered-organization contemplated-organization reflected-organization pondered-organization meditated-organization thought-organization cogitated-organization ruminated-organization speculated-organization hypothesized-organization theorized-organization conjectured-organization surmised-organization guessed-organization estimated-organization approximated-organization projected-organization forecasted-organization predicted-organization anticipated-organization expected-organization awaited-organization hoped-organization wished-organization desired-organization wanted-organization needed-organization required-organization demanded-organization requested-organization asked-organization looked-organization trailed-organization shadowed-organization stalked-organization surveyed-organization inspected-organization examined-organization investigated-organization explored-organization studied-organization researched-organization analyzed-organization judged-organization rated-organization ranked-organization scored-organization graded-organization
Macrosiphoniella sanborni
Chrysanthemum Aphid, Brown Chrysanthemum Aphid
Macrosiphoniella sanborni, the chrysanthemum aphid, is a phloem-feeding aphid in the family Aphididae. It is an oligophagous pest specialized on Chrysanthemum species and a major economic threat to chrysanthemum cultivation. The species exhibits wing dimorphism, with alate (winged) and apterous (wingless) morphs showing distinct chemosensory gene expression profiles. It vectors chrysanthemum viruses including vein mottle virus and virus B.
aphid pest chrysanthemum vector parthenogenesis wing-dimorphism olfaction virus-vector agriculture biological-control

Subscribe to the newsletter

Email address

youtube tiktok snapchat instagram threads facebook twitter

Mike Porter

•

© 2026

•

•

Tailwind Nextjs Theme