Blog WotD About Glossary

Transmission-efficiency

Guides

Lygus hesperus
Western Tarnished Plant Bug
Lygus hesperus is a significant agricultural pest in western North America, causing extensive damage to cotton, strawberries, alfalfa seed, and other crops. In California alone, annual losses exceed $30 million in cotton and $40 million in strawberries. Adults overwinter in reproductive diapause triggered by short day lengths, resuming activity when conditions improve. The species has been the subject of extensive research on sampling methods, biological control, and insecticide resistance.
agricultural-pest plant-bug Miridae cotton-pest strawberry-pest alfalfa-pest western-North-America diapause biological-control integrated-pest-management insecticide-resistance mark-release-recapture salivary-enzymes extraoral-digestion Peristenus-relictus Hippodamia-convergens drone-sampling fluorescent-marking SmartWater vector Pantoea-ananatis Serratia potassium-chloride deterrent artificial-diet lentil seed-crops California Texas Arizona Nevada Washington Mexico polyphagous phytophagous stylet-probing scutellum nymph-spots economic-entomology organic-agriculture ecosystem-services bird-predation molecular-gut-analysis ELISA immunomarking parasitoid population-suppression crop-protection sampling-protocols sweep-net drop-cloth Y-tube-olfactometer gustatory-deterrent visual-cues volatile-cues reproductive-diapause postdiapause oogenesis oviposition longevity body-mass life-history mass-spectrometry salivary-proteins polygalacturonase α-amylase protease laccase glucose-dehydrogenase xanthine-dehydrogenase plant-defense host-pathogen-interaction iDrone-Bee UAV unmanned-aerial-vehicle open-source field-scouting IPM economic-threshold Bt-cotton natural-enemy conservation-biological-control landscape-ecology habitat-management weed-management border-sprays spot-treatment selective-insecticide neonicotinoid pyrethroid resistance-management sustainable-agriculture food-security economic-impact simulation-model population-dynamics immigration parasitism averted-loss value-loss cost-benefit research-methodology insect-marking dispersal fluorophore autofluorescence survivorship mortality mark-transfer crowding olfactometer feeding-behavior no-choice-assay choice-assay gustation host-selection plant-quality succulent-growth fruiting-structures square boll bloom terminal defoliation stand-loss dirty-bloom puckered-petals lesion carpel-wall lint-damage seed-damage yield-loss fiber-quality management-threshold scouting-interval action-threshold treatment-timing insecticide-efficacy labeled-rate difficult-to-control species-complex identification-key morphology color-variation wing-development antennae thorax abdomen instar developmental-stage laboratory-rearing oligidic-diet semisolid-slurry chicken-egg soybean wheat-germ lima-bean cost-reduction biomass-production survival fecundity egg-production generation-time population-growth log-phase colony-maintenance genetic-diversity field-collection adaptation stress-tolerance oxidative-stress temperature-extreme food-deficit resource-allocation reproductive-senescence endogenous-reserves environmental-stressor climate-adaptation phenology migration dispersal-pattern habitat-patch source-sink population-source population-sink crop-border field-edge non-crop-habitat refuge overwintering-site spring-emergence summer-population fall-population density-dependence aggregation spatial-distribution sampling-accuracy pest-detection monitoring-technology precision-agriculture digital-agriculture automation robotics machine-learning computer-vision sensor-technology data-collection decision-support grower-education extension stakeholder-engagement multidisciplinary-research academia-industry-collaboration sustainable-intensification agroecosystem food-system plant-insect-interaction insect-plant-coevolution salivary-secretion digestive-enzyme lytic-enzyme tissue-maceration feeding-injury physiological-damage mechanical-damage wound-response plant-defense-response induced-resistance systemic-acquired-resistance jasmonic-acid ethylene salicylic-acid secondary-metabolite phenolic-compound oxidative-enzyme redox-enzyme bacterial-transmission phytopathogen opportunistic-pathogen infection-court inoculum disease-vector epidemiology crop-hygiene sanitation crop-rotation cover-crop trap-crop push-pull habitat-manipulation conservation-biocontrol augmentative-biocontrol classical-biocontrol importation establishment non-target-effect host-specificity parasitoid-biology reproductive-parasitoid idiobiont koinobiont mummy-formation emergence-rate parasitoid-impact population-regulation top-down-control bottom-up-control trophic-cascade food-web ecosystem-function ecosystem-service disservice net-effect risk-assessment management-strategy policy regulation pesticide-registration resistance-monitoring stewardship integrated-resistance-management IRM refuge-strategy pyramid-strategy multiple-toxins transgenic-crop GMO biosafety environmental-impact non-target-organism pollinator-protection beneficial-insect natural-enemy-conservation floral-resource nectar pollen alternative-prey habitat-diversification agri-environment-scheme green-infrastructure ecological-compensation landscape-complexity connectivity matrix-quality spillover source-habitat ecological-trap population-viability extinction-risk invasion-biology range-expansion climate-change warming drought irrigation water-stress nitrogen-fertilization crop-vigor plant-nutrition host-plant-quality tritrophic-interaction plant-microbe-insect endosymbiont gut-microbiome salivary-microbiome vector-competence transmission-efficiency acquisition inoculation retention multiplication circulative non-circulative persistent non-persistent propagative stylet-borne foregut-borne hemolymph-borne salivary-gland-borne replication barrier midgut salivary-gland escape infection incubation latent-period inoculation-threshold transmission-threshold epidemic epiphytotic disease-triangle susceptible-host virulent-pathogen favorable-environment disease-cycle primary-inoculum secondary-inoculum overwintering-pathogen survival-structure disease-reservoir alternative-host volunteer-crop weed-reservoir crop-residue soilborne seedborne insect-borne management-tactic preventive curative eradicative suppressive protectant systemic contact translaminar fumigant biological-pesticide microbial-pesticide entomopathogenic-fungus entomopathogenic-nematode entomopathogenic-virus baculovirus granulovirus nucleopolyhedrovirus bacteria Bacillus-thuringiensis Bt-toxin crystal-protein cytolytic-protein vegetative-insecticidal-protein mode-of-action gut-paralysis septicemia toxemia antibiotic symbiont antibiotic-resistance fitness-cost resistance-allele resistance-mechanism metabolic-resistance target-site-resistance penetration-resistance behavioral-resistance cross-resistance multiple-resistance resistance-evolution selection-pressure dose-response lethal-concentration lethal-dose median-lethal-concentration median-lethal-dose confidence-interval probit-analysis logit-analysis dose-mortality time-mortality resistance-ratio resistance-factor diagnostic-dose discriminating-dose baseline-susceptibility susceptible-strain reference-strain field-population resistant-population homozygous-resistant heterozygous dominance recessive incomplete-dominance gene-frequency allele-frequency selection-coefficient fitness relative-fitness population-genetics quantitative-genetics heritability genetic-correlation breeding-value genetic-gain marker-assisted-selection genomic-selection transcriptomics proteomics metabolomics genomics functional-genomics comparative-genomics evolutionary-genomics population-genomics phylogenomics bioinformatics computational-biology systems-biology network-analysis pathway-analysis gene-ontology protein-protein-interaction signal-transduction hormone juvenile-hormone ecdysone insulin-like-peptide neuropeptide pheromone sex-pheromone aggregation-pheromone alarm-pheromone trail-pheromone kairomone allomone synomone semiochemical olfaction mechanoreception vision phototaxis chemotaxis anemotaxis thermotaxis hygrotaxis geotaxis kinesis taxis orthokinesis klinokinesis rheotaxis thigmotaxis contact-chemoreception olfactory-receptor gustatory-receptor ionotropic-receptor odorant-binding-protein chemosensory-protein sensillum sensory-neuron antennal-lobe mushroom-body lateral-horn central-complex optical-lobe compound-eye ocellus simple-eye photoreceptor rhabdom ommatidium facet visual-acuity motion-detection polarized-light-detection color-vision ultraviolet-vision infrared-detection thermoreception hygroreception mechanoreceptor chordotonal-organ campaniform-sensillum trichoid-sensillum basiconic-sensillum coeloconic-sensillum placoid-sensillum sensory-ecology foraging-behavior host-location host-acceptance host-suitability oviposition-preference oviposition-deterrence antixenosis antibiosis tolerance resistance-category gall-midge hessian-fly gene-for-gene avirulence-gene resistance-gene R-gene effector-triggered-immunity pattern-triggered-immunity pathogen-associated-molecular-pattern damage-associated-molecular-pattern microbe-associated-molecular-pattern recognition perception defense-response hypersensitive-response cell-death programmed-cell-death autophagy necrosis oxidative-burst reactive-oxygen-species nitric-oxide calcium-signaling mitogen-activated-protein-kinase transcription-factor defense-gene pathogenesis-related-protein antimicrobial-peptide phytoalexin lignin suberin callose papilla cell-wall-reinforcement hypersensitive-cell-death induced-systemic-resistance priming defense-elicitor plant-activator biostimulant plant-strengthener organic-amendment compost manure biochar vermicompost compost-tea microbial-inoculant plant-growth-promoting-rhizobacteria mycorrhizal-fungus endophyte epiphyte phytosphere rhizosphere phyllosphere spermosphere anthroposphere ecosystem-process nutrient-cycling carbon-sequestration nitrogen-fixation phosphorus-solubilization potassium-mobilization micronutrient-availability soil-structure water-infiltration water-holding-capacity erosion-control pollination pest-suppression disease-suppression weed-suppression decomposition detritivory predation herbivory mutualism commensalism competition facilitation inhibition amensalism neutralism symbiosis antagonism trophic-interaction food-chain energy-flow material-cycling biomass-pyramid trophic-pyramid ecological-efficiency production-efficiency assimilation-efficiency ecological-footprint sustainability resilience resistance adaptability transformability socio-ecological-system adaptive-management participatory-research citizen-science knowledge-co-production transdisciplinary-research interdisciplinary-research disciplinary-research basic-research applied-research development-research action-research participatory-action-research farmer-participatory-research on-farm-research station-research controlled-experiment field-experiment observational-study correlational-study manipulative-experiment natural-experiment quasi-experiment longitudinal-study cross-sectional-study case-study comparative-study meta-analysis systematic-review scoping-review rapid-review living-review evidence-synthesis knowledge-synthesis research-synthesis systematic-map bibliometric-analysis citation-analysis co-citation-analysis bibliographic-coupling keyword-analysis topic-modeling science-mapping research-front emerging-topic hot-topic research-gap future-direction research-priority research-agenda strategic-research mission-oriented-research societal-challenge sustainable-development-goal nutrition-security climate-smart-agriculture climate-resilient-agriculture low-input-agriculture regenerative-agriculture agroecology integrated-farming mixed-farming diversified-farming specialized-farming intensive-farming extensive-farming conventional-farming alternative-farming urban-agriculture peri-urban-agriculture rural-agriculture smallholder-agriculture large-scale-agriculture family-farming corporate-farming contract-farming tenant-farming subsistence-farming commercial-farming export-oriented-farming import-substituting-farming local-food-system global-food-system food-value-chain supply-chain value-chain commodity-chain agribusiness agrifood-system food-processing food-distribution food-retail food-service food-consumption food-waste food-loss post-harvest-loss storage-loss processing-loss distribution-loss retail-loss consumer-waste plate-waste kitchen-waste food-rescue food-recovery food-redistribution food-banking composting anaerobic-digestion bioenergy biofuel bioproduct biomaterial biorefinery circular-economy circular-bioeconomy green-economy blue-economy bioeconomy nature-based-solution ecosystem-based-adaptation ecosystem-based-mitigation climate-mitigation disaster-risk-reduction extreme-event flood heat-wave cold-snap frost hail windstorm tornado hurricane typhoon cyclone storm-surge sea-level-rise salinization desertification land-degradation soil-degradation soil-erosion soil-compaction soil-sealing soil-contamination soil-pollution heavy-metal persistent-organic-pollutant pesticide-residue antibiotic-residue hormone-residue plastic-pollution microplastic nanoplastic particulate-matter air-pollution water-pollution groundwater-pollution surface-water-pollution eutrophication hypoxia dead-zone biodiversity-loss habitat-loss habitat-fragmentation habitat-degradation habitat-destruction invasive-species introduced-species alien-species non-native-species exotic-species naturalized-species casual-species escaped-species cultivated-species ornamental-species pet-species livestock poultry aquaculture fishery capture-fishery marine-fishery freshwater-fishery inland-fishery recreational-fishery subsistence-fishery artisanal-fishery industrial-fishery overfishing bycatch discards ghost-fishing fishing-gear fishing-method fishing-effort fishing-capacity fishing-pressure stock-assessment fishery-management marine-protected-area no-take-zone marine-reserve terrestrial-protected-area national-park nature-reserve wildlife-sanctuary biosphere-reserve world-heritage-site ramsar-site important-bird-area key-biodiversity-area ecological-network protected-area-network conservation-corridor wildlife-corridor habitat-corridor stepping-stone buffer-zone transition-zone core-zone management-zone sustainable-use-zone restoration-zone rehabilitation-zone reclamation-zone remediation-zone containment-zone eradication-zone surveillance-zone monitoring-zone quarantine-zone biosecurity phytosanitary veterinary animal-health plant-health one-health ecohealth planetary-health global-health public-health environmental-health occupational-health food-safety feed-safety water-safety air-quality environmental-quality environmental-monitoring environmental-assessment environmental-impact-assessment strategic-environmental-assessment cumulative-impact-assessment social-impact-assessment health-impact-assessment hazard-assessment exposure-assessment dose-response-assessment risk-characterization risk-management risk-communication risk-perception risk-governance precautionary-principle polluter-pays-principle user-pays-principle extended-producer-responsibility corporate-social-responsibility environmental-stewardship sustainable-livelihood sustainable-consumption sustainable-production green-procurement green-supply-chain green-logistics green-manufacturing green-chemistry green-technology clean-technology environmental-technology pollution-prevention waste-minimization resource-efficiency energy-efficiency water-efficiency material-efficiency land-use-efficiency nutrient-use-efficiency nitrogen-use-efficiency phosphorus-use-efficiency potassium-use-efficiency micronutrient-use-efficiency fertilizer-use-efficiency pesticide-use-efficiency water-productivity land-productivity labor-productivity capital-productivity total-factor-productivity partial-factor-productivity agricultural-productivity crop-productivity livestock-productivity fishery-productivity forestry-productivity economic-productivity social-productivity environmental-productivity ecological-productivity biological-productivity primary-productivity secondary-productivity net-primary-productivity gross-primary-productivity ecosystem-productivity landscape-productivity regional-productivity global-productivity carbon-productivity nitrogen-productivity water-footprint carbon-footprint nitrogen-footprint phosphorus-footprint biodiversity-footprint material-footprint land-footprint energy-footprint emission-factor intensity-factor decoupling absolute-decoupling relative-decoupling resource-decoupling impact-decoupling dematerialization rematerialization transmaterialization substitution complementarity trade-off synergy co-benefit win-win lose-lose win-lose zero-sum positive-sum negative-sum game-theory prisoner's-dilemma tragedy-of-the-commons collective-action common-pool-resource public-good private-good club-good common-good global-common global-public-good tipping-point critical-transition regime-shift hysteresis irreversibility path-dependence lock-in technological-lock-in institutional-lock-in behavioral-lock-in social-ecological-trap poverty-trap degradation-trap development-trap complex-adaptive-system social-ecological-system coupled-human-natural-system human-environment-system adaptive-capacity transformative-capacity learning-capacity innovation-capacity governance-capacity institutional-capacity organizational-capacity individual-capacity community-capacity social-capital human-capital natural-capital physical-capital financial-capital built-capital cultural-capital political-capital intellectual-capital knowledge-capital information-capital data-capital digital-capital technological-capital infrastructural-capital institutional-capital organizational-capital network-capital relationship-capital reputational-capital brand-capital symbolic-capital existential-capital spiritual-capital religious-capital moral-capital ethical-capital trust-capital reciprocity-capital solidarity-capital cooperation-capital coordination-capital collaboration-capital communication-capital information-sharing knowledge-sharing learning innovation experimentation transformation transition change evolution development growth progress improvement enhancement optimization maximization minimization satisfaction sufficiency abundance scarcity security insecurity vulnerability robustness stability instability equilibrium disequilibrium homeostasis allostasis stress distress eustress coping coping-capacity coping-strategy coping-mechanism coping-resource coping-support social-support emotional-support instrumental-support informational-support appraisal-support network-support community-support institutional-support policy-support financial-support technical-support technological-support infrastructural-support capacity-building capacity-development capacity-strengthening empowerment enablement mobilization activation engagement participation involvement inclusion exclusion marginalization discrimination inequity inequality disparity gap divide digital-divide knowledge-divide information-divide science-divide research-divide innovation-divide technology-divide development-divide north-south-divide east-west-divide urban-rural-divide gender-divide age-divide class-divide income-divide wealth-divide asset-divide opportunity-divide outcome-divide wellbeing-divide happiness-divide life-satisfaction-divide health-divide education-divide skill-divide competency-divide capability-divide functioning-divide agency-divide freedom-divide choice-divide autonomy-divide self-determination-divide dignity-divide respect-divide recognition-divide status-divide power-divide influence-divide voice-divide representation-divide participation-divide engagement-divide citizenship-divide belonging-divide identity-divide culture-divide value-divide belief-divide norm-divide practice-divide behavior-divide habit-divide custom-divide tradition-divide modernity-divide globalization-divide localization-divide universalism-divide particularism-divide cosmopolitanism-divide nationalism-divide patriotism-divide populism-divide elitism-divide democracy-divide authoritarianism-divide control-divide security-divide liberty-divide privacy-divide surveillance-divide transparency-divide accountability-divide responsibility-divide liability-divide guilt-divide blame-divide punishment-divide reward-divide incentive-divide motivation-divide intention-divide attention-divide perception-divide cognition-divide emotion-divide affect-divide attitude-divide preference-divide interest-divide need-divide want-divide desire-divide demand-divide supply-divide market-divide exchange-divide transaction-divide contract-divide agreement-divide cooperation-divide competition-divide conflict-divide coercion-divide force-divide violence-divide peace-divide harmony-divide coexistence-divide tolerance-divide acceptance-divide rejection-divide opposition-divide resistance-divide conformity-divide deviance-divide normality-divide abnormality-divide illness-divide disease-divide disorder-divide disability-divide impairment-divide handicap-divide capacity-divide potential-divide performance-divide achievement-divide attainment-divide accomplishment-divide success-divide failure-divide excellence-divide mediocrity-divide average-divide standard-divide benchmark-divide threshold-divide ceiling-divide floor-divide limit-divide boundary-divide border-divide frontier-divide horizon-divide perspective-divide viewpoint-divide standpoint-divide position-divide stance-divide approach-divide method-divide technique-divide tool-divide instrument-divide device-divide apparatus-divide equipment-divide machine-divide machinery-divide mechanism-divide system-divide structure-divide organization-divide institution-divide regime-divide order-divide arrangement-divide configuration-divide pattern-divide design-divide plan-divide scheme-divide program-divide project-divide initiative-divide intervention-divide action-divide activity-divide operation-divide process-divide procedure-divide protocol-divide guideline-divide recommendation-divide requirement-divide regulation-divide rule-divide law-divide policy-divide strategy-divide tactic-divide objective-divide goal-divide target-divide aim-divide purpose-divide mission-divide vision-divide principle-divide ethic-divide moral-divide criterion-divide indicator-divide measure-divide metric-divide index-divide scale-divide score-divide rating-divide ranking-divide grade-divide level-divide stage-divide phase-divide step-divide progression-divide sequence-divide series-divide succession-divide chain-divide cycle-divide loop-divide spiral-divide wave-divide pulse-divide rhythm-divide tempo-divide pace-divide speed-divide velocity-divide acceleration-divide deceleration-divide momentum-divide inertia-divide energy-divide work-divide effort-divide strain-divide stress-divide pressure-divide tension-divide compression-divide expansion-divide contraction-divide deformation-divide distortion-divide transformation-divide conversion-divide transduction-divide transmission-divide transfer-divide transport-divide movement-divide motion-divide flow-divide flux-divide current-divide stream-divide river-divide tide-divide wind-divide storm-divide weather-divide climate-divide season-divide year-divide decade-divide century-divide millennium-divide epoch-divide era-divide period-divide time-divide duration-divide interval-divide span-divide stretch-divide spell-divide bout-divide episode-divide event-divide occurrence-divide incident-divide accident-divide coincidence-divide chance-divide luck-divide fortune-divide destiny-divide fate-divide karma-divide dharma-divide tao-divide way-divide path-divide road-divide route-divide course-divide direction-divide orientation-divide alignment-divide positioning-divide placement-divide location-divide site-divide place-divide spot-divide point-divide situation-divide context-divide environment-divide setting-divide scene-divide platform-divide base-divide foundation-divide ground-divide soil-divide earth-divide land-divide terrain-divide territory-divide domain-divide realm-divide sphere-divide world-divide globe-divide planet-divide universe-divide cosmos-divide space-divide void-divide emptiness-divide fullness-divide plenum-divide vacuum-divide atmosphere-divide air-divide gas-divide vapor-divide mist-divide fog-divide cloud-divide rain-divide snow-divide ice-divide frost-divide dew-divide humidity-divide moisture-divide wetness-divide dryness-divide aridity-divide drought-divide flood-divide deluge-divide inundation-divide submersion-divide immersion-divide saturation-divide supersaturation-divide condensation-divide evaporation-divide transpiration-divide sublimation-divide deposition-divide precipitation-divide infiltration-divide percolation-divide seepage-divide leakage-divide discharge-divide runoff-divide erosion-divide sedimentation-divide accretion-divide aggregation-divide coagulation-divide flocculation-divide crystallization-divide solidification-divide liquefaction-divide vaporization-divide boiling-divide melting-divide freezing-divide thawing-divide cooling-divide heating-divide warming-divide thermal-divide temperature-divide heat-divide cold-divide cool-divide warm-divide hot-divide thermodynamic-divide enthalpy-divide entropy-divide free-energy-divide Gibbs-free-energy-divide Helmholtz-free-energy-divide chemical-potential-divide fugacity-divide partial-pressure-divide concentration-divide dilution-divide solution-divide mixture-divide compound-divide element-divide atom-divide molecule-divide ion-divide electron-divide proton-divide neutron-divide nucleus-divide particle-divide quark-divide lepton-divide boson-divide fermion-divide hadron-divide baryon-divide meson-divide photon-divide gluon-divide weak-boson-divide Higgs-boson-divide string-divide brane-divide dimension-divide space-time-divide continuum-divide discrete-divide quantum-divide classical-divide relativistic-divide Newtonian-divide Einsteinian-divide Planckian-divide cosmological-divide astronomical-divide microscopic-divide macroscopic-divide mesoscopic-divide nanoscopic-divide atomic-divide molecular-divide cellular-divide tissue-divide organ-divide organism-divide population-divide community-divide ecosystem-divide biome-divide biosphere-divide ecosphere-divide noosphere-divide technosphere-divide anthroposphere-divide sociosphere-divide politosphere-divide econosphere-divide culturosphere-divide religiosphere-divide ideosphere-divide memesphere-divide infosphere-divide cybersphere-divide digisphere-divide virtual-divide analog-divide real-divide actual-divide possible-divide impossible-divide necessary-divide contingent-divide probable-divide improbable-divide certain-divide uncertain-divide determinate-divide indeterminate-divide definite-divide indefinite-divide specific-divide general-divide particular-divide universal-divide singular-divide plural-divide individual-divide collective-divide social-divide cultural-divide historical-divide political-divide economic-divide religious-divide philosophical-divide scientific-divide technological-divide artistic-divide literary-divide musical-divide visual-divide performing-divide cinematic-divide photographic-divide architectural-divide fashion-divide culinary-divide gastronomic-divide olfactory-divide gustatory-divide tactile-divide kinesthetic-divide proprioceptive-divide vestibular-divide auditory-divide somatosensory-divide interoceptive-divide exteroceptive-divide multisensory-divide crossmodal-divide synesthetic-divide anesthetic-divide esthetic-divide aesthetic-divide poetic-divide rhetorical-divide logical-divide mathematical-divide statistical-divide computational-divide algorithmic-divide heuristic-divide systematic-divide methodical-divide empirical-divide theoretical-divide conceptual-divide abstract-divide concrete-divide practical-divide applied-divide pure-divide fundamental-divide basic-divide strategic-divide tactical-divide operational-divide administrative-divide managerial-divide executive-divide leadership-divide followership-divide membership-divide partnership-divide ownership-divide stewardship-divide guardianship-divide trusteeship-divide custodianship-divide wardship-divide tutelage-divide mentorship-divide sponsorship-divide championship-divide friendship-divide relationship-divide kinship-divide companionship-divide fellowship-divide scholarship-divide apprenticeship-divide internship-divide residency-divide assistantship-divide associateship-divide authorship-divide editorship-divide curatorship-divide directorship-divide governorship-divide presidency-divide chancellorship-divide deanship-divide headship-divide chairmanship-divide