The Little Known World of Flies - Biology Education

18I WONDER... MAGAZINE SUBHEAD

THE LITTLE-KNOWNWORLD OF FLIES!

Geetha Iyer

ToknowtheflyistoshareabitinthesublimityofKnowledge.-ProfVincentGDethier

Whatmakesfliesdifferentfromadragonflyorabutterfly?Howdothelovelyiridescentbluebottleandgreenbottleflieshelpsolvemurders?Whatdoinsectbites,gallsandchocolatehaveincommon?Doflieshavetaste-buds?Howdoweintroducefliesinscienceclassrooms?Thisarticleexploresthefascinatingworldoftrueflies,theirincrediblevariety,andthediversityofservicestheyprovideuswith,endingwithanactivitythatteacherscanusetounravelalittlethoughtofaspectofflylifetostudents.

Introduction

Fliesgenerallyconjureavisionofdirt,diseaseanddisgust.

Ourintroductiontothisimageoffliesisinschool.Astudentisintroducedtothehumblehouseflyinaconclusivemanner,leavingonewiththeimpressionthatallfliesarerepulsivecreatures.Limitedscientificinformationabouthousefliesisaccompaniedbyavividdescriptionofthemouthpartsbeingusedtodrinkfrommuck,therebyleavinganindelibleimageofaflyonlyasavermin.Astudents’nextencounterwiththeflyisduringalessononhealth,asthecarrierofdiseases,therebynailingthecoffinonthepossibilityoffliesbeinganythingbutloathsomecreatures.

Nodoubttherearemanyfliesthatbiteandspreaddisease.But,doallfliesdeservesuchanimage?It’stimesomeonespokeupforflies,whosecolour,varietyandeleganceshouldnotbejudgedonlybythehousefly,orthebehaviourrestrictedtoafrolicindecomposingheaps,althoughthisfrolicisnot

SECTION HEADER

Brown Muscid Fly

withoutbenefit,andIshallsoontellyouhowandwhy.

Althoughtherearemanyinterestingaspectsoffliesthatonecandwellon,inthisarticle.Iwillconfinemyselftointroducingyoutoasmallgrouponecanchanceupon,eveninurbanenvironments;andtothediversityandservicessomefliesinthisorderperform.Ishallconcludewithhowthemouthpartsofahouseflycanbeobservedinamannerthatismoreinterestingthanlookingataslide,withartificialcolours,underamicroscope.

Arefliesfilthy?

Fliesareamongthecleanestofinsects,andareveryparticularabouttheirownhygiene.Infact,humanscouldtakealessonortwoonpersonalhygienefromthem.Observeaflycloselynexttime,andyouwillnoticehowfrequentlyitcleansitself.

Ifaflydoesvisitdecomposingmaterialsforitsnutrientrequirements,itdoessotosatisfyitsnutritionalneeds.Afterall,wehumans,too,likefoodgrowingondecomposingmatter,don’twe?Ifyouweretotakeasurveyofyourdailyintakeoffood,you’dbesurprisedbyhowmanyofourfavouritefoodscomefromdecomposingmatter!Takemushrooms,forexample,thatgrowsoverywelloncowdung;orKombucha,ahealthdrink,madebyallowingcertainyeastandbacterialspecies(kombuchacultureappearinglikeaslimypancake)togrowinasugarysolutionofblackorgreentea!Whatavarietyoffermentingfooditemsweconsume!

Perhaps,someoftheblameforthediseasesthatfliestransmitliesinhumanstoo!Ifwegavemorethoughttoourhygieneandsanitation,flieswouldn’tfrequentourenvironmentsofreely,wouldthey?

Whatisafly?

InaworldpopulatedbytheButterfly,Dragonfly,Scorpionfly,Mayfly,Stonefly,Firefly,Owlfly,andsoon,whatisthisinsectthatissimplycalledafly?

Theinsectslistedabovearenotfliesfromanentomologists’pointofview.TruefliesareinsectsthatbelongtotheorderDiptera,anamethatdescribestheirdefiningfeature–theseflieshaveonlyonepairofwings(inLatin,di:meanstwo,andptera:meanswings).Incontrast,insectsbelongingtoallotherinsectordershavetwopairsofwings!Whatmakesthisevenmoreinteresting

Twowingsseemtohavemadethemnolessagilethanotherinsects,eminentlydeservingthename“fly”!Considerthesefacts,notlearntinaclassonflies.Fliesareincrediblynimbleinflight.Thebestaerialistsamonginsects,theycanhover,flybackwards,turninplaceandflyupsidedowntolandontheceiling!Theyhavesensors-speedindicators-locatedinapartoftheirantennacalledarista,togaugetheirflightspeed.Ahousefly’swingspeedisabout190beatsinasinglesecond!Thefastestmuscularcontractionahumanbeingcanmanageclocksattentimespersecond.Nomysterythen,whyitissodifficulttoswatafly!

Howmanyfliesarethereintheworld?

Nooneknowsanexactnumber.Asmentionedbefore,truefliesbelongtotheorderDiptera,whichisthethirdlargestgroupamonginsects.Mosquitoesbelongtothisordertoo!Morethan1,60,000speciesofflieshavealreadybeendescribedbyspecialists;withverymanymoreyettobeclassified,andseveralmoretobediscovered.Asyoucantell,thismeansaverylargenumber,indeed!

FlyServicesandDiversity

Everyfamilyofanimals(includinghumans)onthisplanet,havetheirshareofvillainsandheroes;and,flyfamiliesarenoexception!Therearemany

isthattrueflieshaveevolvedfromfour-wingedancestorsinthePermian250MYA(millionyearsago).Intheirmodern-daydescendants,however,thissecondpair-thehindwings-hasbecomereducedtoclub-shapedstructures,calledHalteres.Eachhalterecanbelikenedtoagyroscope;theyareessentialinmaintainingbalanceduringflight.

interestingthingsonecanlearnbyexploringtheworldofflies.Ishalldescribeahandfulofthesehere.

A.FliesasPollinators:Itisawell-establishedfactthatplantsandinsectshavemutuallyinfluencedtheevolutionoftheirdiversity.Fliesarebelievedtobeforemostamongstthepollinatorsofearlyfloweringplants;yettheirroleinsuchanimportantserviceremainsrelativelyunknown.Ofthe150dipteranfamilies,flyspeciesofnearly70families(Evenhuisetal.2008)areknowntovisitflowerstofeed.Ithasbeendocumentedthatfliesaretheprimarypollinatorsforseveralhundredsofwildorcultivatedplants(closeto550,accordingtoLarsenetal.2001).Pollinationbyfliesis,generally,referredtoasmyophily.

Whatmakesfliessuchgoodpollinators?Theyarenotonlyabundant,butarealsopresentinwidelydiversehabitats.Theyarethemostimportantpollinatorsinalpineorarcticregions,wherepollinationbybeesisreduced.Intheunder-storeyregionsofforests,fliesarebelievedtobeimportantinpollinatingawidevarietyofshrubswithsmall,inconspicuousordioeciousflowers.Theirabundantpresenceiscomplimentedbyanatomicalfeatures,suchasvariationsinmouthparts,tonguelength,sizeanddegreeofpilosity(hairiness);allofwhichcontributetomakingfliessomeofthemosteffectivepollinators,ever.Plantswouldprobablynodtheir(flower)headsinagreement!

Fliesvisitflowersfortheirownreasons:nectarandpollenaresourcesoffood.Theproteinsinpollenarenecessaryforsomefliestoreproduce.Somefliesvisitflowerstolaytheireggs,ensuringthattheirdevelopinglarvaehaveeasyaccesstofood–theflowerheads,seedsordevelopingfruits.And,so,forsomeflies,flowersaremating(dating?)sites.Howconvenient!

Myfavouriteamongthesepollinators,withoutdoubt,wouldbethebeautifulandcolourfulfliesoftheFamilySyrphidae,commonlycalledhoverfliesorflowerflies.Atfirstglance,ahoverflywouldhardlystrikeoneasafly,lookingmorelikeabee,thanafly.Eachofthem,however,hassuchalongproboscis,thatitcangointothedeepestofcorollastosipnectar.Thismakesthemexcellentpollinators,servingawiderangeofplants,andsecondonlytobeesinthisrole.Alargenumberoffoodsweconsumearepollinatedbyhoverflies.Lookforthesefliesamongsttheflowersofmango,apple,pear,cherry,andstrawberry;oramong

Chrysops sp. Biting fly.

coriander,onion,carrot,pepper,andcapsicum,tonameafew.

Thelifeofaninsectisfulloftricksandtreatsthatcontributetoitssurvival.Onesuchfeatureisthedifferingfoodsourceforlarvaeandadults.Adultinsectsdon’tcompetewiththeiryoungonesforfood.Thus,whiletheadulthoverflyisavegetarianhelpingwithpollination;it’slarvaeormaggotsareinsectivorous,feedingonawiderangeofprey-mostlyaphidsandothersapsuckinginsects,andtherebyactingaspestcontrolagents-anotherfactaboutfliesthatrarelyreceivesanyattention.Thus,syrphidfliesareimportantaspollinatorsandpestcontrollers.

Hover fly Mesembrius quadrivittatus.

Blow fly-Blue bottle fly, Calliphora sp.

Plantsputoutavarietyofodourstoattractinsects.Theputridsmellofdecayingfleshfromsomeflowersattractscarrionanddungflies,belongingtotheFamilyCalliphoridae.Theyvisittheseflowers,expectingtofinddecayingfleshand,pollinatethem,evenastheyleavedisappointed.Commonlycalledblowflies,thebluebottleandgreenbottlefliesarequitecolourfulandattractive.Interestingly,theyplayanimportantroleinforensics(seebelow).

withoutbenefit,andIshallsoontellyouhowandwhy.

Althoughtherearemanyinterestingaspectsoffliesthatonecandwellon,inthisarticle.Iwillconfinemyselftointroducingyoutoasmallgrouponecanchanceupon,eveninurbanenvironments;andtothediversityandservicessomefliesinthisorderperform.Ishallconcludewithhowthemouthpartsofahouseflycanbeobservedinamannerthatismoreinterestingthanlookingataslide,withartificialcolours,underamicroscope.

Arefliesfilthy?

Fliesareamongthecleanestofinsects,andareveryparticularabouttheirownhygiene.Infact,humanscouldtakealessonortwoonpersonalhygienefromthem.Observeaflycloselynexttime,andyouwillnoticehowfrequentlyitcleansitself.

Ifaflydoesvisitdecomposingmaterialsforitsnutrientrequirements,itdoessotosatisfyitsnutritionalneeds.Afterall,wehumans,too,likefoodgrowingondecomposingmatter,don’twe?Ifyouweretotakeasurveyofyourdailyintakeoffood,you’dbesurprisedbyhowmanyofourfavouritefoodscomefromdecomposingmatter!Takemushrooms,forexample,thatgrowsoverywelloncowdung;orKombucha,ahealthdrink,madebyallowingcertainyeastandbacterialspecies(kombuchacultureappearinglikeaslimypancake)togrowinasugarysolutionofblackorgreentea!Whatavarietyoffermentingfooditemsweconsume!

Perhaps,someoftheblameforthediseasesthatfliestransmitliesinhumanstoo!Ifwegavemorethoughttoourhygieneandsanitation,flieswouldn’tfrequentourenvironmentsofreely,wouldthey?

Whatisafly?

InaworldpopulatedbytheButterfly,Dragonfly,Scorpionfly,Mayfly,Stonefly,Firefly,Owlfly,andsoon,whatisthisinsectthatissimplycalledafly?

Theinsectslistedabovearenotfliesfromanentomologists’pointofview.TruefliesareinsectsthatbelongtotheorderDiptera,anamethatdescribestheirdefiningfeature–theseflieshaveonlyonepairofwings(inLatin,di:meanstwo,andptera:meanswings).Incontrast,insectsbelongingtoallotherinsectordershavetwopairsofwings!Whatmakesthisevenmoreinteresting

Twowingsseemtohavemadethemnolessagilethanotherinsects,eminentlydeservingthename“fly”!Considerthesefacts,notlearntinaclassonflies.Fliesareincrediblynimbleinflight.Thebestaerialistsamonginsects,theycanhover,flybackwards,turninplaceandflyupsidedowntolandontheceiling!Theyhavesensors-speedindicators-locatedinapartoftheirantennacalledarista,togaugetheirflightspeed.Ahousefly’swingspeedisabout190beatsinasinglesecond!Thefastestmuscularcontractionahumanbeingcanmanageclocksattentimespersecond.Nomysterythen,whyitissodifficulttoswatafly!

Howmanyfliesarethereintheworld?

Nooneknowsanexactnumber.Asmentionedbefore,truefliesbelongtotheorderDiptera,whichisthethirdlargestgroupamonginsects.Mosquitoesbelongtothisordertoo!Morethan1,60,000speciesofflieshavealreadybeendescribedbyspecialists;withverymanymoreyettobeclassified,andseveralmoretobediscovered.Asyoucantell,thismeansaverylargenumber,indeed!

FlyServicesandDiversity

Everyfamilyofanimals(includinghumans)onthisplanet,havetheirshareofvillainsandheroes;and,flyfamiliesarenoexception!Therearemany

isthattrueflieshaveevolvedfromfour-wingedancestorsinthePermian250MYA(millionyearsago).Intheirmodern-daydescendants,however,thissecondpair-thehindwings-hasbecomereducedtoclub-shapedstructures,calledHalteres.Eachhalterecanbelikenedtoagyroscope;theyareessentialinmaintainingbalanceduringflight.

interestingthingsonecanlearnbyexploringtheworldofflies.Ishalldescribeahandfulofthesehere.

A.FliesasPollinators:Itisawell-establishedfactthatplantsandinsectshavemutuallyinfluencedtheevolutionoftheirdiversity.Fliesarebelievedtobeforemostamongstthepollinatorsofearlyfloweringplants;yettheirroleinsuchanimportantserviceremainsrelativelyunknown.Ofthe150dipteranfamilies,flyspeciesofnearly70families(Evenhuisetal.2008)areknowntovisitflowerstofeed.Ithasbeendocumentedthatfliesaretheprimarypollinatorsforseveralhundredsofwildorcultivatedplants(closeto550,accordingtoLarsenetal.2001).Pollinationbyfliesis,generally,referredtoasmyophily.

Whatmakesfliessuchgoodpollinators?Theyarenotonlyabundant,butarealsopresentinwidelydiversehabitats.Theyarethemostimportantpollinatorsinalpineorarcticregions,wherepollinationbybeesisreduced.Intheunder-storeyregionsofforests,fliesarebelievedtobeimportantinpollinatingawidevarietyofshrubswithsmall,inconspicuousordioeciousflowers.Theirabundantpresenceiscomplimentedbyanatomicalfeatures,suchasvariationsinmouthparts,tonguelength,sizeanddegreeofpilosity(hairiness);allofwhichcontributetomakingfliessomeofthemosteffectivepollinators,ever.Plantswouldprobablynodtheir(flower)headsinagreement!

Fliesvisitflowersfortheirownreasons:nectarandpollenaresourcesoffood.Theproteinsinpollenarenecessaryforsomefliestoreproduce.Somefliesvisitflowerstolaytheireggs,ensuringthattheirdevelopinglarvaehaveeasyaccesstofood–theflowerheads,seedsordevelopingfruits.And,so,forsomeflies,flowersaremating(dating?)sites.Howconvenient!

Myfavouriteamongthesepollinators,withoutdoubt,wouldbethebeautifulandcolourfulfliesoftheFamilySyrphidae,commonlycalledhoverfliesorflowerflies.Atfirstglance,ahoverflywouldhardlystrikeoneasafly,lookingmorelikeabee,thanafly.Eachofthem,however,hassuchalongproboscis,thatitcangointothedeepestofcorollastosipnectar.Thismakesthemexcellentpollinators,servingawiderangeofplants,andsecondonlytobeesinthisrole.Alargenumberoffoodsweconsumearepollinatedbyhoverflies.Lookforthesefliesamongsttheflowersofmango,apple,pear,cherry,andstrawberry;oramong

Chrysops sp. Biting fly.

coriander,onion,carrot,pepper,andcapsicum,tonameafew.

Thelifeofaninsectisfulloftricksandtreatsthatcontributetoitssurvival.Onesuchfeatureisthedifferingfoodsourceforlarvaeandadults.Adultinsectsdon’tcompetewiththeiryoungonesforfood.Thus,whiletheadulthoverflyisavegetarianhelpingwithpollination;it’slarvaeormaggotsareinsectivorous,feedingonawiderangeofprey-mostlyaphidsandothersapsuckinginsects,andtherebyactingaspestcontrolagents-anotherfactaboutfliesthatrarelyreceivesanyattention.Thus,syrphidfliesareimportantaspollinatorsandpestcontrollers.

Hover fly Mesembrius quadrivittatus.

Plantsputoutavarietyofodourstoattractinsects.Theputridsmellofdecayingfleshfromsomeflowersattractscarrionanddungflies,belongingtotheFamilyCalliphoridae.Theyvisittheseflowers,expectingtofinddecayingfleshand,pollinatethem,evenastheyleavedisappointed.Commonlycalledblowflies,thebluebottleandgreenbottlefliesarequitecolourfulandattractive.Interestingly,theyplayanimportantroleinforensics(seebelow).

Robustly,builtfliesofthefamilyTabanidae,commonlycalledhorseflies,or,simply,tabanidflies,aremostlybloodthirstyflies;butsomeofthemarelesserfiends.Theyareconsideredpests,sincemanyspeciesbiteanimalsandhumans.But,some,withtheirspectacularlylongtonguespollinateflowersthathavelongtube-shapedcorollas(imageTabanidfly–Philolichesp.).InthefemalesofcertainPhilolichespecies,theverylongtongueisadaptedtoperformthedualfunctionsofbloodsuckingandnectarsipping!Rhino-myophilyisthetermthatdescribespollinationbylong-tonguedflies.

Thatuniversallylovedfood-chocolate,owesitsexistencetoflies!Midgesareflies.ThosebelongingtothefamiliesCeratopogonidaeandCecidomyiidae,areknownmorefortheirbitingandgall-forminghabitsthanforanythingapplaudable.But,notallofthemarebitersorgallers!Thecocoaplantreliesonsmallmidgespeciesofthesetwofamiliestopollinateitstinywhiteblossoms,producedonthelowerpartsofitsmaintrunk.Themushroomishodouroftheflowerattractsmidges,justaschocolatesattractus.Otherthanaparticularspeciesofhoverfliesinsomerestrictedregions,cocoaplantsneedmidgestoproducefruit.Nomidge,nococoa,nochocolates!DoIhearshoutsofthreecheersformidges?Doremembertothankflies,thenexttimeyoufeastonchocolatesorcocoa.

B.FliesinForensics:Fromthelivingtothedead,fromflowerstocorpses-asfliessearchfornutrition,theiractionsbestowindirectassistancetootherlivingorganisms.Flieshelphumansincriminalinvestigations,andareafavouritewithforensicentomologists.

Blowfliesarenotjustpollinators;theirlovefordecomposinganimalmatterdrawsthemtothedead.Infact,theyarethefirsttoarriveatadeath

Blowfly – Greenbottle, Lucilla sp.

Golden blowfly.

Tabanid fly - Philoliche spp. Photo by Sanjay Sondhi

A midge

Otherspeciesofflies,suchastheblacksoldierfly,thecoffinfly,theblackscavengerfly,membersofHydroteasp.ofFamilyMuscidae,andhumpbackedflies,areequallyusefulinprovidingimportantinformationduringautopsies.Theirservicesrangefromdeterminingwhetherthecorpsehasbeenmovedfromtheoriginalsceneofcrime,informationabouttoxicology,and,inmanycases,eveninfixingthetimeofdeath.

“TheWashingAwayofWrongs"writtenin1247ADbySungTz’u,acrimeinvestigatorinChina,isthefirstrecordoffliesincriminalinvestigation.Thisbookisthefirsttolaythefoundationsofforensicentomology.AmurderhappensinaChinesevillage,andthedeadman’sbodyisdiscovered,cutupbadly.Unabletomakeanyheadwaywithhisinvestigation,theinvestigatorasksallthevillagerstobringtheirsickles,andlayitonthegroundinfrontofhim.Soonfliesswarmtoonesickle.Theownerhadnotwashedhissicklewell,andtheflieswereattractedtothe

scene!Soacuteisitssenseofsmell,thatablowflycanapparentlysmelladeadbody16kmaway!Membersofthisfamilyareknownbyvariousnames–bluebottles,greenbottles.Theyareeasilyrecognised-lookinglikealargerversionofthecommonhousefly.Whyaretheydrawntodeadbodies,onemayask?Blowflieslookatdeadbodiesasafoodsourcefortheiryoungones.Theylaytheireggsintheorificesofcorpses,andmaggotshatchoutin24hours.Fleshflies,oftheFamilySarcophagidae,givebirthtoliveyoungonesonthefleshofthecorpses!Howdoesthisbehaviourhelpus?Thelifehistoryofablowflyiswell-documented,providingamineofinformationduringpost-mortemsofthecorpsesthatattractthem.

Flesh Fly

odourofblood.Theownerconfessestothecrime,and,so,begantheuseoffliestosolvecrimes.

IfyouareafanoftheTVserial“Bones”,then,surely,youmustalreadybeawareofthenuancesofforensicentomology,fromtheworkofthecharacterJackHodgins,aforensicentomologist-cum-botanist.

Therearemanyothersuchinterestinginstancesofcrimes,solvedwiththehelpofflies.

C.FliesasPestControlAgents:Agriculturalresearchersandpragmaticfarmerswillvouchfortheservicesprovidedbyfliesinkeepingacheckonphytophagousinsects.Therearemanyfliesthathelpintheseroles,butdescribedbelowareafewfavouritesofmine.

Icallthemjewelflies,andnotlong-leggedflies,astheyaremorecommonlycalled.Theirmorecommonnamepointstotheirlonglegs,astrikingfeatureofthefliesofthefamilyDolichopodidae.Jewelfliesareslenderanddaintylittleflies,sportingbeautifulcolours.Mostlyblue,green,andgoldwithametallicshine,thereareafewoftheseecologicallyimportantfliesthatsportadullgreycolourtoo.Lookingverymuchlikeaflyonstilts;youcannotmissthem.Theyhaveaslenderbody,prominenteyes,andtheirtrademarklonglegs.Malesshowofftheirlonglegstoattractfemales;quitetheoppositeofthehumanspeciesitwouldseem!Lavishmanoeuvresandsignalsmarkthecourtshipbehaviourofmales.Manyofthesefliesmateinflight,whichisanexhaustingpractice;so,sometimesmalescreateanillusionbysportingapatterntoconthefemalesintothinkingthattheyarematinginflight.

Foundinmosthabitats,Jewelfliesarepredatory,feedingonawidevarietyofinvertebrates-aphids,thrips,spidermites,andcollembolans.Infact,aparticularspeciesofDolichopuspreysonmosquitolarvae!Somespeciesarescavengerstoo.Thesefliesarefidgety;soonehastobereallystillandsilenttowatchthem.

Robustly,builtfliesofthefamilyTabanidae,commonlycalledhorseflies,or,simply,tabanidflies,aremostlybloodthirstyflies;butsomeofthemarelesserfiends.Theyareconsideredpests,sincemanyspeciesbiteanimalsandhumans.But,some,withtheirspectacularlylongtonguespollinateflowersthathavelongtube-shapedcorollas(imageTabanidfly–Philolichesp.).InthefemalesofcertainPhilolichespecies,theverylongtongueisadaptedtoperformthedualfunctionsofbloodsuckingandnectarsipping!Rhino-myophilyisthetermthatdescribespollinationbylong-tonguedflies.

Thatuniversallylovedfood-chocolate,owesitsexistencetoflies!Midgesareflies.ThosebelongingtothefamiliesCeratopogonidaeandCecidomyiidae,areknownmorefortheirbitingandgall-forminghabitsthanforanythingapplaudable.But,notallofthemarebitersorgallers!Thecocoaplantreliesonsmallmidgespeciesofthesetwofamiliestopollinateitstinywhiteblossoms,producedonthelowerpartsofitsmaintrunk.Themushroomishodouroftheflowerattractsmidges,justaschocolatesattractus.Otherthanaparticularspeciesofhoverfliesinsomerestrictedregions,cocoaplantsneedmidgestoproducefruit.Nomidge,nococoa,nochocolates!DoIhearshoutsofthreecheersformidges?Doremembertothankflies,thenexttimeyoufeastonchocolatesorcocoa.

B.FliesinForensics:Fromthelivingtothedead,fromflowerstocorpses-asfliessearchfornutrition,theiractionsbestowindirectassistancetootherlivingorganisms.Flieshelphumansincriminalinvestigations,andareafavouritewithforensicentomologists.

Blowfliesarenotjustpollinators;theirlovefordecomposinganimalmatterdrawsthemtothedead.Infact,theyarethefirsttoarriveatadeath

Blowfly – Greenbottle, Lucilla sp.

Golden blowfly.

Tabanid fly - Philoliche spp. Photo by Sanjay Sondhi

A midge

Otherspeciesofflies,suchastheblacksoldierfly,thecoffinfly,theblackscavengerfly,membersofHydroteasp.ofFamilyMuscidae,andhumpbackedflies,areequallyusefulinprovidingimportantinformationduringautopsies.Theirservicesrangefromdeterminingwhetherthecorpsehasbeenmovedfromtheoriginalsceneofcrime,informationabouttoxicology,and,inmanycases,eveninfixingthetimeofdeath.

“TheWashingAwayofWrongs"writtenin1247ADbySungTz’u,acrimeinvestigatorinChina,isthefirstrecordoffliesincriminalinvestigation.Thisbookisthefirsttolaythefoundationsofforensicentomology.AmurderhappensinaChinesevillage,andthedeadman’sbodyisdiscovered,cutupbadly.Unabletomakeanyheadwaywithhisinvestigation,theinvestigatorasksallthevillagerstobringtheirsickles,andlayitonthegroundinfrontofhim.Soonfliesswarmtoonesickle.Theownerhadnotwashedhissicklewell,andtheflieswereattractedtothe

scene!Soacuteisitssenseofsmell,thatablowflycanapparentlysmelladeadbody16kmaway!Membersofthisfamilyareknownbyvariousnames–bluebottles,greenbottles.Theyareeasilyrecognised-lookinglikealargerversionofthecommonhousefly.Whyaretheydrawntodeadbodies,onemayask?Blowflieslookatdeadbodiesasafoodsourcefortheiryoungones.Theylaytheireggsintheorificesofcorpses,andmaggotshatchoutin24hours.Fleshflies,oftheFamilySarcophagidae,givebirthtoliveyoungonesonthefleshofthecorpses!Howdoesthisbehaviourhelpus?Thelifehistoryofablowflyiswell-documented,providingamineofinformationduringpost-mortemsofthecorpsesthatattractthem.

Flesh Fly

odourofblood.Theownerconfessestothecrime,and,so,begantheuseoffliestosolvecrimes.

IfyouareafanoftheTVserial“Bones”,then,surely,youmustalreadybeawareofthenuancesofforensicentomology,fromtheworkofthecharacterJackHodgins,aforensicentomologist-cum-botanist.

Therearemanyothersuchinterestinginstancesofcrimes,solvedwiththehelpofflies.

C.FliesasPestControlAgents:Agriculturalresearchersandpragmaticfarmerswillvouchfortheservicesprovidedbyfliesinkeepingacheckonphytophagousinsects.Therearemanyfliesthathelpintheseroles,butdescribedbelowareafewfavouritesofmine.

Icallthemjewelflies,andnotlong-leggedflies,astheyaremorecommonlycalled.Theirmorecommonnamepointstotheirlonglegs,astrikingfeatureofthefliesofthefamilyDolichopodidae.Jewelfliesareslenderanddaintylittleflies,sportingbeautifulcolours.Mostlyblue,green,andgoldwithametallicshine,thereareafewoftheseecologicallyimportantfliesthatsportadullgreycolourtoo.Lookingverymuchlikeaflyonstilts;youcannotmissthem.Theyhaveaslenderbody,prominenteyes,andtheirtrademarklonglegs.Malesshowofftheirlonglegstoattractfemales;quitetheoppositeofthehumanspeciesitwouldseem!Lavishmanoeuvresandsignalsmarkthecourtshipbehaviourofmales.Manyofthesefliesmateinflight,whichisanexhaustingpractice;so,sometimesmalescreateanillusionbysportingapatterntoconthefemalesintothinkingthattheyarematinginflight.

Foundinmosthabitats,Jewelfliesarepredatory,feedingonawidevarietyofinvertebrates-aphids,thrips,spidermites,andcollembolans.Infact,aparticularspeciesofDolichopuspreysonmosquitolarvae!Somespeciesarescavengerstoo.Thesefliesarefidgety;soonehastobereallystillandsilenttowatchthem.

SoldiersandRobbersperformingsimilarfunctionscouldhappenonlyintheworldofinsects!SoldierfliesbelongtothefamilyStratiomyidaewhereastherobberflies,toFamilyAsilidae.Intheworldofflies,therobbersattackandcatchpestsmoreoftenthanthesoldiers;thelatter’sservicesarevariedandincludesomepredation.

Robberfliesarethemostpredatorygroupintheworldofflies,andfeedexclusivelyoninsects.Theirnameistrulyrepresentativeoftheirbehaviour.Theyareaggressivehunters,ambushtheirprey,andarestronglybuiltwithpowerfulmusclesthathelpthemcaptureinsectsinflight!Theyarerobbersinappearancetoo,sportingatuftofstiffbristles-likeamoustache-betweentheireyes,thataremountedprominentlyontheirhead.Infact,theterm‘mystax’usedtodescribethesebristlesisderivedfromtheGreekwordmeaning‘moustache’or‘upperlip’.Thesecosmopolitanfliesenjoyaworldwidedistribution,butarecommonintropicalandsubtropicalareas,andabundantindryandsunnyaridorsemi-aridzones.

Robberfliescanveryeasilybeidentifiedbytheirlongslenderbodies,withthetipsoftheirabdomensvisiblebeyondthefoldedwings.Themystaxisunmistakable,andtheheadandthoraxishairy.Becauseoftheirlongtaperingabdomen,combinedwithbrightlycoloured–black,grey,redoryellow-patterns,theyareoftenmistakenforwasps.Someofthemwithstout,hairybodies,mimicbees;whileotherswithslender,lithebodies,imitatedamselflies.Asyoucansee,theserobbershavemasteredtheartofdisguisetoo!Theirperchisanotherwayofidentifyingthesefliesinahabitat.Robbersliketoperchonthetopmostendofaplantwaitingtoseizeprey.

Robbersinjectcapturedpreywithsalivacontainingneurotoxicandproteolyticenzymes,killingthem.Bothadultandjuvenilerobberfliespreyonawidevarietyofinsects,thusservingtheimportantecologicalfunctionofkeepingacheckontheinsectfaunainanyarea.

Soldierfliesarediverseintheirhabitsandfoodpreferences,butaremainlyrecognisedbytheiruniquewingvenation.Somesoldiersarepollinators;someassistwithforensics;othersarehelpfulincompostingwaste;whileafewofthemarepredatory.Thebrightlycolouredonesresemblewaspsandbees.Soldiersmaybesaprophagus,myophagousorpredatory;andaregenerallyfoundclosetoaquatichabitatsinwhichtheirlarvaedevelop.Thesefliesarenotawidelyresearchedgroup,exceptHermetiaillucens,whichiscommonlycalledtheblacksoldierfly.Weshalllookatthisflyagain,inthenextsection.

D.FliesinComposting:Theblacksoldierfly,Hermetiaillucens,isnowbeingextensivelyusedtocompostwastes.However,thisprocessisyettofindwiderapplicationinIndia,andiscurrentlybeingpractisedonlybyafewresearchersinPune.

Long-legged flies

Green Soldier Fly

Small Soldier Fly

Black Soldier Fly

Soldier Fly Crane Fly

Mating Robber Flies

Thecompostpitinmybackyardhasblacksoldierflies.Thephotogivenhereisofoneofthemhelpingdecomposewaste,alongwithotherorganisms.

E.FliesinScientificResearch:Fruitflieshavebeeninourlaboratoriesfordecadesnow,andcontinuetoplayawell-knownandextensivelydocumentedroleinoureffortstounderstandgeneactionandinheritancemechanisms.

Whatislesswell-knownistheroleoffliesinsomeotherkindsofexperiments.In2007,forexample,someresearchersatHarvardUniversitybuiltaroboticfly.Weighing60mg,andwithawingspanof3cm,thislife-likeflywasmodelledtoimitatethemovementsofarealfly.Madeofultra-thincarbonfibre,theroboticflyhasawingbeatof110beats/second.Thiseffortisthefirststepto

SoldiersandRobbersperformingsimilarfunctionscouldhappenonlyintheworldofinsects!SoldierfliesbelongtothefamilyStratiomyidaewhereastherobberflies,toFamilyAsilidae.Intheworldofflies,therobbersattackandcatchpestsmoreoftenthanthesoldiers;thelatter’sservicesarevariedandincludesomepredation.

Robberfliesarethemostpredatorygroupintheworldofflies,andfeedexclusivelyoninsects.Theirnameistrulyrepresentativeoftheirbehaviour.Theyareaggressivehunters,ambushtheirprey,andarestronglybuiltwithpowerfulmusclesthathelpthemcaptureinsectsinflight!Theyarerobbersinappearancetoo,sportingatuftofstiffbristles-likeamoustache-betweentheireyes,thataremountedprominentlyontheirhead.Infact,theterm‘mystax’usedtodescribethesebristlesisderivedfromtheGreekwordmeaning‘moustache’or‘upperlip’.Thesecosmopolitanfliesenjoyaworldwidedistribution,butarecommonintropicalandsubtropicalareas,andabundantindryandsunnyaridorsemi-aridzones.

Robberfliescanveryeasilybeidentifiedbytheirlongslenderbodies,withthetipsoftheirabdomensvisiblebeyondthefoldedwings.Themystaxisunmistakable,andtheheadandthoraxishairy.Becauseoftheirlongtaperingabdomen,combinedwithbrightlycoloured–black,grey,redoryellow-patterns,theyareoftenmistakenforwasps.Someofthemwithstout,hairybodies,mimicbees;whileotherswithslender,lithebodies,imitatedamselflies.Asyoucansee,theserobbershavemasteredtheartofdisguisetoo!Theirperchisanotherwayofidentifyingthesefliesinahabitat.Robbersliketoperchonthetopmostendofaplantwaitingtoseizeprey.

Robbersinjectcapturedpreywithsalivacontainingneurotoxicandproteolyticenzymes,killingthem.Bothadultandjuvenilerobberfliespreyonawidevarietyofinsects,thusservingtheimportantecologicalfunctionofkeepingacheckontheinsectfaunainanyarea.

Soldierfliesarediverseintheirhabitsandfoodpreferences,butaremainlyrecognisedbytheiruniquewingvenation.Somesoldiersarepollinators;someassistwithforensics;othersarehelpfulincompostingwaste;whileafewofthemarepredatory.Thebrightlycolouredonesresemblewaspsandbees.Soldiersmaybesaprophagus,myophagousorpredatory;andaregenerallyfoundclosetoaquatichabitatsinwhichtheirlarvaedevelop.Thesefliesarenotawidelyresearchedgroup,exceptHermetiaillucens,whichiscommonlycalledtheblacksoldierfly.Weshalllookatthisflyagain,inthenextsection.

D.FliesinComposting:Theblacksoldierfly,Hermetiaillucens,isnowbeingextensivelyusedtocompostwastes.However,thisprocessisyettofindwiderapplicationinIndia,andiscurrentlybeingpractisedonlybyafewresearchersinPune.

Long-legged flies

Green Soldier Fly

Small Soldier Fly

Black Soldier Fly

Soldier Fly Crane Fly

Mating Robber Flies

Thecompostpitinmybackyardhasblacksoldierflies.Thephotogivenhereisofoneofthemhelpingdecomposewaste,alongwithotherorganisms.

E.FliesinScientificResearch:Fruitflieshavebeeninourlaboratoriesfordecadesnow,andcontinuetoplayawell-knownandextensivelydocumentedroleinoureffortstounderstandgeneactionandinheritancemechanisms.

Whatislesswell-knownistheroleoffliesinsomeotherkindsofexperiments.In2007,forexample,someresearchersatHarvardUniversitybuiltaroboticfly.Weighing60mg,andwithawingspanof3cm,thislife-likeflywasmodelledtoimitatethemovementsofarealfly.Madeofultra-thincarbonfibre,theroboticflyhasawingbeatof110beats/second.Thiseffortisthefirststepto

GeethaIyerisanAuthorandIndependentconsultantworkinginthetwinfieldsofEducationandEnvironment.Shehaswrittenextensivelyontopicsineducation,environmentandNaturalHistory.DrIyercanbereachedatbrownfishowl@yahoo.co.uk

buildingflyinginsectsthatcanbemountedwithsensors,tofunctionasspies.‘Flyonthewall’willsoonbecomeareality,andnotjustbeafancyidiom,orsoitseems.Armylaboratorieshavedefinitelyshownagreatinterestintheseflyspies.

F.FliesandSoilFertility:Imagineanoversizedmosquito-thatiswhatacraneflyortipulidfly,belongingtothefamilyTipulidae,lookslike.But,thesimilarityendswiththeirappearance.Thesegentlefliesnotonlydonotbite;adultsdonotfeedatall!Adultfliesliveforabout10to15days.Femalesemergefromtheirpupawithmatureova.Theyseekoutmates,andsoonafter,laytheireggsonmoistsoil,orsometimes,onthesurfaceofwater.Astheyfeed,theirlarvaehelpdecomposeorganicmatter,andincreasemicrobialactivityinthesoil.Theyare,therefore,veryusefulinasoilecosystem,keepingthesoilfertilethroughtheiractivities.

Theyareveryeasilyrecognizedbytheirslenderelongatedbodiesandlegs.Theirlegs,especially,arequitelong.Althoughtheyarefoundworldwide,theirdiversityisgreatestinthetropics.Easilyattractedtolight,youcanseethemclingingtothewallswiththeirlonglegsspreadout.Orifyouareoutforawalkinthemorning,theycanbeseenrestingonleaves.Interestingly,cranefliescanoftenbeseenwalkingaseasilyasflying!

FliesinScienceClassrooms

Thehousefly,nodoubt,willcontinuetobetheonethatstudentswillencountermostoftenintheirlessons.Whynotmakeitinterestingtoteachalessononthemouthpartsofaflyinadifferentway?Mouthpartsareforfeeding,andwhatbetterwaytolearnaboutthemthantoactuallyseeaflyfeeding.

Howdoesonedothis?Tobeginwith,onewould,ofcourse,needalivefly.And,manipulatingasmallflycanbeatrickyaffair!Butwithalittlebitofpractice,youshouldbefine!It’sonlyfairtomentionthatthisinvestigationcallsforalotofpatienceandtime,butiswellworththetimespentindoingit,forIassureyouthatalotmorethanhowaflydetectsorfeedsislearntthroughsuchactivities.Forexample,thisinvestigationwillshowthatfliestastewiththeirfeet!

Leavesomeoverripebananaoramangoaround,andverysoonyouwillseemanyhousefliespayingthemavisit.Useasmallteastraineroramoistclothtotrapafewoftheseflies,andstore

theminsideadrytransparentjar.Donotkeeptoomanyoftheminsideonejar.

Thenextfewstepsarethetrickyones.Takethreeglassslides,andnumberthem1,2and3.Putafewdropsofwateron1and,2,andsugarsolutionon3.

Thestepfollowingthishastobedoneveryquickly.SmearsomeFevicol(notFeviquick,pleasenote)onyourforefinger,openthejarwiththetrappedflies,andtouchthethoraxofthenearestflywithyourforefinger.Theflywillgetstucktoyourfinger.Holditgentlywithyourfingersinsuchawaythatbothitswingsremainfoldedonitsback.Don’tworry-attheendofthisexperiment,youcanreleasetheflybywashingyourforefingerinwater.Theflywillbewetforsometime(youcangentlydabitdrywithacloth),butwillsoondryitselfout,andfly.

Theflywillbestressedbecauseofitscaptivity.Whenyougentlyloweritclosetothewater-droponslide1,youcanactuallyseeitsproboscispopoutofitsheadtodrinkwater.Whenithasfinisheddrinkingwater,takeitofffromslideone,andnowloweritontothewaterdropinslidetwoinsuchawaythatitsfeettouchthewater.Doyouseetheprobosciscomingdown?

Now,repeatthesamewithslidethree,andyouwillseethatassoonasitslegstouchthesugarsolution,outpopsthefly’sproboscistofeedonthesugarsolution.Youmaynowtrydifferentkindsoffood,andinvestigatethefly’sfeedingpreferencesorhowmuchitneedstofeedon,etc.Seeinganinsectfeedcreatesanactivelearningatmosphereintheclassroom,whichcanthenbefollowedupwithanatomicaldetailsunderthemicroscope.

Conclusion

Thisisbutasmallintroductiontoafewfamiliesoffliesthatmaybefoundmorecommonlyinourhumanenvironments,andarebigenoughtoberecognised.Morethan1,60,000speciesofflies,andstillcounting-makesmeagreewithNash,whenhesays:

GodinhiswisdomMadetheflyAndthenforgotTotelluswhy

–OgdenNash

References

1.Oneproboscis,twotasks:Adaptationstoblood-feedingandnectar-extractinginlong-proboscidhorseflies(Tabanidae,Philoliche).KarolyiaFlorianetal.ArthropodStructure&Development,Vol.43:Issue5,Sept2014:403-413.

2.Theuseofinsectsinforensicinvestigations:Anoverviewonthescopeofforensicentomology.Josephetal.JournalofForensicDentalSciences,Vol.3(2);Jul-Dec2011:89-91.URL:www.ncbi.nlm.nih.gov/pmc/articles/PMC3296382/

3.Lordsoftheflies:theinsectdetectives.JonHenley.TheGuardian:ForensicScience.Sep23,2010.URL:http://www.theguardian.com/science/2010/sep/23/flies-murder-natural-history-museum.

4.Courtshipinlong-leggedflies(Diptera:Dolichopodidae):functionandevolutionofsignals.MartinZimmer,OlafDiestelhorst,andKlausLunau.BehavioralEcology,Vol.14,No.4:526–530.URL:http://beheco.oxfordjournals.org/content/14/4/526.full.pdf

5.RobberFlies(Asilidae).FritzGeller-Grimm,TorstenDikow&RobertJ.Lavigne.URL:http://www.geller-grimm.de/asilidae.htm.

6.OccurrenceofBlackSoldierFlyHermetiaillucens(Diptera:Stratiomyidae)inBiocompost.GujarathiGayatriR.andPejaverMadhuriK.ResearchJournalofRecentSciences,Vol.2(4),April(2013):65-66.URL:http://www.isca.in/rjrs/archive/v2/i4/9.ISCA-RJRS-2012-469.pdf.

7.Blacksoldierflyfarming.URL:http://www.blacksoldierflyfarming.com/.