Entomology 3rd edition - C.Gillott - Chapter 24 docx

24 In s ect s an d Human s 1 . Intr oduc t ion T his final chapter will focus on those insects that humans describe, in their economicall y minded wa y , as beneficial or harmful, thou g h it should be appreciated from the outset that t hese constitute onl y aver y small fraction of the total number of species. It must als o b e rea li ze d t h at t h e eco l og i ca l pr i nc i p l es govern i ng t h e i nteract i ons b etween i nsects an d h umans are no diff erent f rom t h ose b etween i nsects an d any ot h er li v i ng spec i es, eve n th ou gh h umans w i t h t h e i rmo d ern tec h no l o gy can mo dify cons id era bly t h e nature o f t h es e interactions . Of an estimated 5–10 million species of insects, probabl y not more than a fraction o f 1% i nteract, di rect l yor i n di rect l y, w i t hh umans. Per h aps some 10,000 const i tute pests t h at , e i t h er a l one or i n con j unct i on w i t h m i croorgan i sms, cause s i gn ifi cant d amage or d eat h t o h umans, a g r i cu l tura l or f orest pro d ucts, an d manu f acture dg oo d s. Wor ld w id e f oo d an dfib er losses caused b y pests (principall y insects, plant patho g ens, weeds, and birds) are g enerall y estimated at about 40%, of which 12% are attributable to insects and mites. These fi g ures do not i nc l u d e p ost h arvest l osses, est i mate d to b ea b out 20%, an d occur d es pi te t h ea ppli cat i on of about 3 million tonnes of pesticide (worth more than US$31 billion, including abou t US$9 billion of insecticide) (Pimentel, 2002). In the United States alone, crop losses relate d t o insect dama g e rose from 7% to 13% in the period 1945–1989, despite a tenfold increase in the amount of insecticide used ( > 120,000 tonnes each y ear) (Pimente l et al. , 1992) . On t h eot h er h an d ,t h eva l ue o fb ene fi ts d er i ve df rom i nsects i s severa lf o ld t h at o fl osses as a resu l to f t h e i rpo lli nat i ng act i v i ty, t h e i rro l e i n bi o l og i ca l contro l ,an d t h e i r i mportance a s h one y ,s ilk ,an d wax pro d ucers. T h at i nsects d o more g oo d t h an h arm pro b a bly wou ld com e as a surprise to la y persons whose familiarit y with insects is normall y limited to mosquitoes, h ouseflies, cockroaches, various g arden pests, etc., and to farmers who must protect thei r livestock and crops against a variety of pests. If asked to prepare a list of useful insects, man y peop l e most lik e l ywou ld not get f urt h er t h an t h e h oney b ee an d , per h aps, t h es ilk mot h ,an d w ou ld ent i re l y over l oo k t h e enormous num b er o f spec i es t h at act as po lli nat i ng agents or pre y on harmful insects that mi g ht otherwise reach pest proportions. H umans have lon g reco g nized the importance of insects in their well-bein g . Insects and/or their products have been eaten by humans for thousands of years. Production of sil k from silkmoth pupae has been carried out for almost 5 000 years. Locust swarms, which 7 2 5 72 6 CHAPTER 24 o ri g inall y ma y have beenan important seasonal food for humans, took on new si g nificance as humans turned to a farmin g rather than a huntin g existence. However, with rare exceptions, f or example, the hone y bee and silkmoth whose mana g ement is relativel y simple and labor - i ntens i ve, unt il recent l y h umans ne i t h er d es i re d nor were a bl e, b ecause o f a l ac k o fb as i c k now l e d ge as we ll as tec h no l ogy, to attempt l arge-sca l emo difi cat i on o f t h eenv i ronmen t o f insects , either to increase the number of beneficial insects or to decrease the number of those desi g nated as pests . Several features of recent human evolution have made such attem p ts im p erative. These i nc l u d e a mass i ve i ncrease i n popu l at i on, a tren d towar d ur b an i zat i on, i ncrease d geograp hic m ovement o f peop l ean d agr i cu l tura l pro d ucts, an d , assoc i ate d w i t h t h e nee d to f ee d more peop l e, a tren d towar d monocu l ture as an a g r i cu l tura l pract i ce. T he relativel y crowded conditions of urban areas enable insects parasitic on humans both to locate a host (frequentl y a prerequisite to reproduction) and to transfer between hos t i n di v id ua l s. T h us, ur b an i zat i on f ac ili tates t h es p rea d o fi nsect- b orne h uman di seases suc h as typ h us, p l ague, an d ma l ar i aw h ose spectacu l ar e ff ects on h uman popu l at i on are we ll d ocumente d . For examp l e, i nt h es i xt h centur y A.D. p l a g ue was respons ibl e f or t h e d eat h o f about 50% of the p o p ulation in the Roman Em p ire, and “Black Death” killed a similar proportion of En g land’s population in the mid-1300s (Southwood, 1977). An i ncreas i ng nee d to pro d uce more an d c h eaper f oo dl e d ,t h roug h agr i cu l tura l mec h - an i zat i on, to t h e pract i ce o f monocu l ture, t h e grow i ng o f a crop over t h e same l arge area o f l an df or man yy ears consecut i ve ly . However, two f au l ts o f monocu l ture are (1) t h e ecos y s - tem is simplified and (2) as the crop plant is frequentl yg raminaceous (a member of the g ras s f amil y , includin g wheat, barle y , oats, rice, and corn), the ecos y stem is artificiall y maintained at an ear l y stage o f eco l og i ca l success i on. By s i mp lif y i ng t h e ecosystem, h umans encourage t h e b u ild up o f popu l at i ons o f t h e i nsects t h at compete w i t h t h em f or t h e f oo db e i ng grown. Furt h er,ast h e compet i ng i nsects are pr i mary consumers, t h at i s, near t h e start o f t h e f oo d c hain, the y t y picall y haveahi g h reproductive rate and short g eneration time. In other words , p o p ulations of such s p ecies have the p otential to increase at a ra p id rate . A massive increase in human geographic movements and a concomitant increase i n tra d e l e d to t h e transp l antat i on o f a num b er o f spec i es, b ot h p l ant an d an i ma l , i nto area s prev i ous l y unoccup i e db yt h em. Some o f t h ese were a bl e to esta bli s h t h emse l ves an d, i n the absence of normal re g ulators of population (especiall y predators and parasitoids) , i ncreased rapidl y in number and became important pests. Sometimes, as humans colonized n ew areas, some of the cultivated p lants that were introduced p roved to be an excellent food f or s p ec i es o fi nsects en d em i ctot h ese areas. For exam pl e, t h eCo l ora d o b eet l e, L ept i notarsa d ecem l ineata , w a sor i g i na ll y restr i cte d to t h e sout h ern Roc k y Mounta i ns an df e d on w ild S o l anaceae. W i t h t h e i ntro d uct i on o f t h e potato by sett l ers, t h e b eet l e h a d an a l ternate, mor e e asil y accessible source of food, as a result of which both the abundance and distribution of the beetle increased and the species became an important pest. Likewise, the apple ma gg ot, Rh a g o l etis pomone lla , apparent l y f e d on h awt h orn unt il app l es were i ntro d uce di nto t h e e astern United States (Horn, 197 6 ) . 2 . Beneficial Insect s Insects may b ene fi t h umans i nvar i ous ways, b ot hdi rect l yan di n di rect l y. T h e most ob v i ous o f t h e b ene fi c i a l spec i es are t h ose w h ose pro d ucts are commerc i a lly va l ua bl e. Considerabl y more important, however, are the insects that pollinate crop plants. Othe r 7 27 I N S E C T SA ND HUM A NS b eneficial insects are those that are used as food, for biolo g ical control of pest insects and plants, in medicine and in research. For some of these useful species, humans modif y their environment so as to increase their distribution and abundance in order to g ain the benefits . 2 .1. Insects Whose Products Are C ommerc i ally Valuabl e The best-known insects in this category are the honey bee ( Apis mellifera ( ( ) , silkworm ( B ombyx mor i ), lac insect ( L acci f er lacc a ) , and p ela wax scale ( Ericerus pel a ). T h e h oney b ee or i g i na ll y occup i e d t h eA f r i can cont i nent, most o f Europe (except t h e nort h ern part), an d western As i a, an d w i t hi nt hi s area t h e use f u l ness o fi ts pro d ucts, h oney an db eeswax, h as b een k nown f or man y t h ousan d so fy ears. T h ou gh t h e di scover y o f su g a r in cane (in India, about 500 B.C.) and in beet (in Europe, about 1800 A.D.) (Southwood, 1977) led to a decline in the importance of hone y , it is nevertheless still a ver y valuable p roduct . Bee management was pro b a bl y fi rst carr i e d out b yt h e anc i ent Egypt i ans. Honey b ees w ere brought to North America by colonists in the early l 6 00s, and today honey an d b eeswax production is a billion dollar industr y . In 2001 world hone y production was esti- mated at about 1.25 million tonnes and a value of about US $ 4 billion. China is the world’ s largest honey producer, accounting for almost 20% of the total; the United States lies i n thi r d p l ace ( b e hi n d t h e f ormer USSR), pro d uc i ng a b out 100,000 tonnes (w i t h ava l ue o f about US$330 million )( www. b ee k eepin g .com/ d ata b ases/ h one y -mar k et/wor ld h one y . h tm ) . B eeswax is produced at the rate of about 1 k g for ever y 50–100 k g of hone y ; its value per k ilo g ram varies between one and three times that of hone y . There is a si g nificant worl d trade, perhaps worth about US $ 10 million annually, in pollen which is used not only b y b ee k eepers to supp l ement t h e reserves i nt h e hi ve b ut a l so i nt h e h ea l t h - f oo di n d ustry . O ther products that are collected include propolis (bee g lue), venom (used to desensitiz e patients with severe aller g ies to bee stin g s), and ro y al j ell y which is added to certain foo d su pp lements (Gochnauer, in Pimentel, 1991, Vol. 2). Goo db ee management a i ms to ma i nta i na h oney b ee co l ony un d er opt i mum con di t i on s f or max i mum pro d uct i on. Mana g ement d eta il svar y accor di n g to t h ec li mate an d custom s o f different g eo g raphical areas but ma y include (1) movin g hives to locations where nectar - producin g plants are plentiful, (2) artificial feedin g of newl y established, sprin g colonie s wi t h sugar syrup i nor d er to b u ild up co l ony s i ze i nt i me f or t h e summer nectar fl ow , ( 3) c h ec ki ng t h at t h e queen i s l ay i ng we ll an d , if not, rep l ac i ng h er, (4) c h ec ki ng an d treatin g colonies for diseases such as foulbrood and nosema, and ( 5 ) increasin g the size o f ah iv eas the colon y develops, in order to prevent swarmin g. Silk production has been commercially important for about 4700 years. The industr y o r i g i nate di n East As i aan d sprea di nto Europe (France, Ita l y, an d Spa i n) a f ter eggs wer e smugg l e df rom C hi na to Ita l y i nt h es i xt h century A.D. T h e pro d uct i on o f s ilk rema i n s a labor-intensive industr y , makin g production costs hi g h. In 1988 world silk productio n totaled about 67,000 tonnes, with raw silk fetchin g about US $ 50 per kilo g ram. B y the en d of 1998, pro d uct i on h a di ncrease d s li g h t l y, to 72,000 tonnes, t h oug h t h epr i ce o f raw s ilk h a d f allen to about US$26 per kilogram due to competition from cheaper synthetic fibers. Chin a i st h e l ea di n g pro d ucer, w i t h a b out 70% o f t h ewor ld tota l ,an d In di a h as passe d Japan a s the world’s second lar g est producer (Feltwell, 1990 ; www.tradeforum.org/news/fullstor y ) . T he lac insect is a scale insect endemic to India and S outheast Asia that secretes abou t i tse lf a coat i ng o fl ac, w hi c h may b e more t h an1cmt hi c k .T h etw i gs on w hi c h t h e i nsect s rest are co ll ecte d an d e i t h er use d to sprea d t h e i nsects to new areas or groun d up an dh eate d 7 28 CHAPTER 24 i n order to separate the lac. The lac is a component of shellac, thou g h its importance ha s declined considerabl y with the development of s y nthetic materials . T he p ela wax scale has been used in China for commercial p roduction of “China wax, ” pr i nc i pa ll y i nS i c h uan prov i nce, f or more t h an 1000 years. It i st h e secon d - i nstar ma l es t h at pro d uce econom i ca ll yva l ua bl e wax. T h ese are care f u ll y manage di n l arge aggregat i on s ( 200 per c m 2 , and extendin g a distance of 1.0–1. 5 m alon g a branch) that produce a coatin g o f wax some 5–10 mm thick. Wax production peaked in the earl y 1900s and in a g oo d y ear was more than 6000 tonnes. Most of this wax was used in the manufacture of candles . S tart i ng i nt h e 1940s, w i t h t h e com i ng o f e l ectr i c i ty an ddi scovery o f ot h er waxes (nota bl y paraffin wax), interest in China wax production declined, and currently about 5 00 tonne s i s h arveste dy ear ly .It i s use df or a var i et y o fi n d ustr i a l ,p h armaceut i ca l ,an dh ort i cu l tura l p ur p oses, for exam p le, the manufacture of molds for p recision instruments, insulation o f e lectrical cables and equipment, production of hi g h- g loss, tracin g , and wax paper, as a n i ngre di ent o ff urn i ture an d automo bil epo li s h es, coat i ng can di es an d p ill s, an d as a gra f t i ng agent f or f ru i t trees (Q i n, i n Ben-Dov an d Ho d gson, 1994) . 2.2. In sec t sas P o ll i n a t o r s As was noted in Cha p ter 23, Section 3.2, an intimate, mutualistic relationshi p ha s ev o l ve db etween many spec i es o fi nsects an d p l ants, i nw hi c h p l ants pro d uce nectar an d po ll en f or use b y i nsects, w hil et h e l atter prov id e a transport system to ensure e ff ect i ve cross- pollination. Thou g h some crop plants are wind-pollinated, for example, cereals, a lar ge n umber, includin g fruits, ve g etables, and field crops such as clovers, rape, and sunflower, re q uire the service of insects. In addition, ornamental flowers are almost all insect- p ollinated . Th e b est k nown, t h oug hb y no means t h eon l y, i mportant i nsect po lli nator i st h e h oney b ee, an di t i s stan d ar d pract i ce i n many parts o f t h ewor ld f or f ru i t, see d ,an d vegeta bl e pro d ucers e i t h er to set up t h e i rown b ee hi ves i nt h e i r orc h ar d san dfi e ld s or to contract t his j ob out to beekeepers. For example, in California about 1.4 million hives are rented annuall y to au g ment natural pollination of almonds (about 50% of the hives), alfalfa, melons, an d o t h er f ru i ts an d vegeta bl es (P i mente l e ta l. , 1992). Un d er suc h con di t i ons, t h eva l ue o fb ees as po lli nators may b eupto140t i mes t h e i rva l ue as h oney pro d ucers. Us i ng t hi s f actor, it i s est i mate d t h at t h e i ncrea s e d v a l ue o f crops attr ib uta bl eto h one yb ee po lli nat i on i nt h e United States is about US $ 15 billion each y ear [see Robinson et al. ( 1989 ) for a detaile d anal y sis]. This estimate does not take into account the value of other, natural pollinators o f crops, nor obviously has a value been placed on the importance o f a l l p ollinators o f n on-crop p l ants, w hi c h are v i ta l to spec i es di vers i ty an d as f oo df or w ildlif e. 2.3. Insects as A g ents o f B i olo gi cal C ontrol It is only relatively recently that humans have gained an appreciation of the importanc e of i nsects i nt h eregu l at i on o f popu l at i ons o f potent i a ll y h arm f u l spec i es o fi nsects an d p l ants. In many i nstances, t hi s apprec i at i on was ga i ne d on l yw h en, as a resu l to fh uman act i v i t y ,t h e natura l re g u l ators were a b sent, a s i tuat i on t h at was rap idly exp l o i te dby t h ese species whose status was soon elevated to that of pest. In the first three examples g ive n below (taken from DeBach and Rosen, 1991), none of the or g anisms is a pest in its countr y of or i g i n b ecause o f t h e occurrence t h ere o f var i ous i nsect regu l ators. T h e di scovery o f t h ese regu l ators, f o ll owe db yt h e i r success f u l cu l ture an d re l ease i nt h e area w h ere t h e pest o ccurs, const i tutes bi o l o gi ca l contro l (Sect i on 4.3). 7 29 I N S E C T SA ND HUM A NS Amon g the best-known examples of an introduced plant pest are the prickl y pear cacti ( Op untia s pp.) taken into Australia as ornamental plants b y earl y settlers. Once established , t he plants spread rapidl y so that b y 1925 some 60 million acres of land were infested, most l y i n Queens l an d an d New Sout h Wa l es. Surveys i n b ot h Nort h an d Sout h Amer i ca, wh er e Op untia s pp. are endemic, revealed about 1 5 0 species of cactus-eating insects, of w hich about 5 0 were j ud g ed to have biolo g ical control potential and were subsequentl y sent to Australia for culture and trials. Larvae of one s p ecies, C actoblastis cactoru m ,a moth, brou g ht from Ar g entina in Januar y , 1925, proved to have the required qualities and wi t hi n 10 years h a d v i rtua ll y d estroye d t h e cact i (F i gure 24.1). Per h aps t h e most remar k a ble feature of this success story is that only 27 5 0 C acto bl astis l arvae were b roug h t to Austra li a , o f w hi c h on l y 1070 b ecame a d u l ts. From t h ese, h owever, more t h an 100,000 eggs were produced, and in Februar y –March of 192 6 more than 2.2 million e gg s were released in t he field! Additional releases, and redistribution of almost 400 million field-produced e gg s u ntil the end of 1929, ensured the project’s success . T h ec l ass i ca l examp l eo f an i nsect pest b roug h tun d er bi o l og i ca l contro li st h e cottony- cus hi on sca l e , I cer y a purc h as i , w hi c h was i ntro d uce di nto Ca lif orn i a, pro b a bl y f rom Australia, in the l8 6 0s. Within 20 y ears, the scale had virtuall y destro y ed the recentl y established, citrus-fruit industr y in southern California. As a result of correspondence be - t ween American and Australian entomologists and of a visit to Australia by an America n entomo l og i st, A lb ert Koe b e l e, two i nsect spec i es were i ntro d uce di nto t h eUn i te d State s as bi o l og i ca l contro l agents f or t h e sca l e. T h e fi rst, i n 1887, was Cr y ptoc h aetum icer y a e , a parasitic fl y , about which little is heard, thou g h DeBach and Rosen (1991) consider tha t it had excellent p otential for control of the scale had it alone been im p orted. However, th e abilities of this species appear to have been lar g el y i g nored with the discover y b y Koebele o f th eve d a li a b eet l e , Ro d o l ia car d ina l i s , feeding on the scale. In total, only 514 vedalia were b roug h t i nto t h eUn i te d States, b etween Novem b er 1888 an d Marc h 1889, to b ecu l ture d on ca g e d trees i n f este d w i t h sca l e. B y t h een d o f Ju ly 1889, t h eve d a li a h a d repro d uce d to suc h an extent that one orchardist, on whose trees about 150 of the im p orted beetles had been placed for culture, reported havin g distributed 63,000 of their descendants since June 1! B y 1890, t h e sca l e was v i rtua ll yw i pe d out. S i m il ar successes i n contro lli ng sca l e b y means o f v e d a li ao r C r y ptoc h aetu m have been reported from more than 60 countries (Hokkanen, in P i mente l , 1991, Vo l .2 ) . A third example of an introduced pest bein g brou g ht under control b y biolo g ical a g ents is the winter moth, Operophtera brumata, which, thou g h endemic to Europe and parts of Asia, was accidentally introduced into Nova Scotia in the 1930s. Its initial colonization wa s slow, and it did not reach economically significant proportions until the early 19 5 0s, and b y 19 6 2 it had spread to Prince Edward Island and New Brunswick. The larvae of the winter moth feed on the folia g e of hardwoods such as oak and apple. Thou g h more than 6 0 para- sites of the winter moth are known in western Europe, onl y 6 of these were considered to be potential control agents and introduced into eastern Canada between 1955 and 1960. Two o f t h ese, C y zenis a lb icans , a tac hi n id ,an d Ag r y pon flaveo l atu m ,an i c h neumon id , b ecame established, but between them they brought the moth under control by 19 6 3. Embree (i n Hu ff a k er, 1971) note d t h at t h e two paras i tes are b ot h compat ibl ean d supp l ementar y t o each other. When the densit y of moth larvae is hi g h, C . a lbicans, which is attracted to , and la y s its e gg s near, feedin g dama g e caused b y the larvae, is a more efficient parasite tha n A . flaveo l atum . H owever, once i nt h ev i c i n i ty o fd amage, i t d oes not spec ifi ca ll y see k out w i nter mot hl arvae. T h us, at l ower d ens i ty, i t wastes eggs on non-suscept ibl e d e f o li a- t ors suc h as caterp ill ars o f t h e f a ll can k erworm , Al so ph i l a p ometaria. Hence , at l ow h ost 7 30 CHAPTER 24 F I GU RE 24.1. ( A ) C actoblastis cactorum caterpillars feeding on cactus pad; and cactus-infested pasture before (B) an d a f ter (C) re l ease o f C acto bl asti s . [ From D. F. Water h ouse, 1991, Insects an dh umans i n Austra li a, i n: T h e I nsects o f Austra l i a , 2n d e d ., Vo l . 1 (CSIRO, e d .), Me lb ourne Un i vers i t y Press. B y perm i ss i on o f t h eD i v i s i on o f Entomology, CSIRO. ] 7 31 I N S E C T SA ND HUM A NS d ensities , A. fl aveolatu m is more effective because it oviposits specificall y on winter moth larvae. The three examples described above indicate one method whereb y the importance o f bi o l og i ca l contro l can b e d emonstrate d , name l y, b y i ntro d uct i on o f potent i a l pests i nto areas wh ere natura l regu l ators are a b sent. Anot h er way o fd emonstrat i ng t h e same p h enomenon i sto d estro y t h e natura l re g u l ators i nt h eor igi na lh a bi tat, w hi c h ena bl es potent i a l pest s t o under g o a population explosion. This has been achieved frequentl y throu g h the use of non-selective insecticides. For example, the use of DDT a g ainst the codlin g moth , Cydi a p omone ll a, i n th ewa l nut orc h ar d so f Ca lif orn i a, l e d to out b rea k so f nat i ve f roste d sca l e, Lecanium pruinosum , w hi c h was una ff ecte db y DDT, w h ereas i ts ma i n pre d ator, an en- cyrt id , M etap h ycus ca l ifornicus , su ff ere dhi g h morta li ty (Hage n et a l. ,in Hu ff a k er, 1971 ) . Another Leca n iu m s cale , L . coryli , introduced from Europe in the 1 6 00s, is a potentiall y serious pest of apple orchards in Nova Scotia but is normall y re g ulated b y various natural parasitoids (especially the chalcidoid s B lastothrix serice a a n d Coccophagu s s p .) and p reda- t ors (especially mirid bugs). Experimentally it was clearly demonstrated in the 1960s that app li cat i on o f DDT d estroye d a l arge proport i on o f t h e B l a s tot h ri x an d m i r id popu l at i on, and this was followed in the next two y ears b y medium to heav y scale infestations. Recover y of the parasite and predators was rapid, however, and b y the third y ear after spra y in g the scale population density had been reduced to its original value (MacPhee and MacLellan , i nHu ff a k er, 1971). 2 . 4 .In sec t sas H u m a nF ood As noted in the previous chapter, insects pla y ake y role in ener gy flow throu g h the ecosystem, pr i nc i pa ll yas h er bi vores b ut a l so as pre d ators or paras i tes, w hi c h may t h em- se l ves b e consume db y hi g h er- l eve li nsect i vorous verte b rates. In turn, some o f t h ese ver- t e b rates, nota bly f res h water fi s h an dg ame bi r d s, are eaten by h umans. Moreover, i n man y parts of the world, insects (includin gg rasshoppers and locusts, beetle larvae, caterpillars, b rood of ants, wasps and bees, termites, cicadas, and various aquatic species) historicall y played, and continue to have, an important part as a normal component of the human diet (DeFo li art, 1992, 1999). A b or i g i na l peop l eo f t h e Great Bas i nreg i on i nt h e sout h western Un i te d States tra - d itionall y spent much time and effort harvestin g a variet y of insects, principall y crickets, g rasshoppers, shore flies (Eph y dridae) (especiall y the pupae), caterpillars, and ants (adult s and pupae) though bees, wasps, stoneflies, aphids, lice, and beetles were also consumed on an opportun i st i c b as i s. Some o f t h e i nsects were eaten raw t h oug h most were b a k e d or roaste d pr i or to b e i ng consume d ; f urt h er, l arge quant i t i es, espec i a ll yo f grass h oppers an d cr i c k ets, w ere dried and g round to produce a flour that was stored for winter use (Sutton, 1988). I n parts of southeastern Australia the abori g inals would seasonall yg or g e themselves on bogong moths ( A grotis in f us a ( ( ) which estivate from December throu g h Februar y in vas t num b ers i n hi g h -a l t i tu d e caves an d roc k y outcrops i nt h e Sout h ern Ta bl e l an d s(F i gure 24.2). Some tr ib es wou ld ma k e an annua l tre k over a cons id era bl e di stance (up to 200 k m) to ta k e a d vanta g eo f t hi s seasona lf oo d source, return i n g eac hy ear to t h e same area (F l oo d , 1980). I n some African countries (includin g Botswana, South Africa, Zaire, and Zimbabwe ) t here is a thrivin g trade in mopanie caterpillars ( G onimbrasia belina), and when these ar e i n season, b ee f sa l es may s h owas i gn ifi cant d ec li ne.As i m il ar pre f erence f or i nsects over meat i ss h own b yt h eYup k a peop l eo f Co l om bi aan d Venezue l a (Ru ddl e, 1973). Insect s are a l so eaten i n man y As i an countr i es; i n d ee d , gi ant water b u g s(Let h oceru s in d icu s ) an d 7 32 CHAPTER 24 B FIGURE 24.2 . ( A) T h e b ogong mot h, Agrotis in f usa;an d (B) est i vat i ng b ogong mot h s f orm i ng a sca l e like p attern on a cave wa ll .A b or igi na l s h arveste d t h e mot h s i n vast num b ers by di s l o dgi n g t h em w i t h st i c k san d collecting them in nets or bark dishes held beneath. [A, photograph by J. Green. B, from D. F. Waterhouse, 1991, Insects an dh umans i n Austra li a, i n: Th e Insects of Austra l i a , 2n d e d ., Vo l . 1 (CSIRO, e d .), Me lb ourne Un i vers i ty Press. B y perm i ss i on o f t h eD i v i s i on o f Entomo l o gy , CSIRO.] 7 33 I N S E C T SA ND HUM A NS pupae of the silkmoth ( B ombyx mori) are exported to Asian communit y food stores i n t he United States from Thailand and South Korea, respectivel y . Mexico also used to shi p food insects to the United States, namel y ahuahutle (Mexican caviar—the e gg s of various aquat i c Hem i ptera) an d maguey worms (caterp ill ars o f Ae g ia l e h esperiari s , f oun d on agave) . S hi pment o f a h ua h ut l e to Nort h Amer i ca no l onger occurs b ecause o fl a k epo ll ut i on, t h oug h i t can st ill b e f oun di n man y mar k ets an d restaurants i nMex i co an di s exporte d to Europe as bird and fish food. Ma g ue y worms are commonl y eaten in Mexico and are exported as g ourmet food to North America, France and Japan (DeFoliart, 1992, 1999). However, t our i sts w h ov i s i tMex i co are pro b a bl y more f am ili ar w i t h anot h er caterp ill ar, t h ere d agav e w orm ( C oma d ia re d ten b ac hi ) , seen i n b ott l es o f mezca l ! T h ere h as b een some i ncrease i n i nterest i nt h e potent i a l o fi nsects as f oo d , i nc l u di n g d iscussion of the sub j ect at international conferences. However, most North Americans and Europeans have not y et been educated to the deli g hts of insects, despite the efforts of authors such as Taylor and Carter (1976), DeFoliart (1992, 1999), and Berenbaum (1995) to i ncrease t h e popu l ar i ty o fi nsects as f oo d .T h e western wor ld ’s bi as aga i nst eat i ng i nsects h a s t wo negat i ve i mpacts. F i rst, i t may b e seen as a m i sse d opportun i ty. Compare d to li vestoc k , insects are much more efficient at convertin g plant material into animal material with hi gh nutritional value. With relativel y little research, industrial-scale mass production of foo d insects should be possible. Second, as less-developed areas of the world become increasingly w estern i ze d ,t h e i r popu l at i ons may b e expecte d to eat f ewer i nsects. T hi s cou ld l ea d t o nutr i t i ona l pro bl ems i n areas w h ere t h e economy i sa l rea d y marg i na l (DeFo li art, 1999) . 2 .5. S oil-Dwellin g and S caven g in g Insect s By t h e i r very h a bi tt h ema j or i ty o f so il - d we lli ng i nsects are i gnore db y h umans. On l y th ose t h at a d verse l ya ff ect our we ll - b e i ng, f or examp l e, term i tes, w i reworms, an d cutworms, norma lly “mer i t” our attent i on. W h en p l ace di n perspect i ve, h owever, i t seems pro b a bl et h at t he dama g e done b y such pests is g reatl y outwei g hed b y the benefits that soil-dwellin g insect s as a g roup confer. The benefits include aeration, draina g e, and turnover of soil as a result of b urrow i ng act i v i ty. Many spec i es carry an i ma l an d p l ant mater i a l un d ergroun df or nest i ng , f ee di ng, an d /or repro d uct i on, w hi c hh as b een compare d to p l oug hi ng i n a cover crop . Many i nsects, i nc l u di ng a l arge num b er o f so il - d we lli ng spec i es, are scavengers; t h at is, the y feed on deca y in g animal or plant tissues, includin g dun g , and thus accelerate the return of elements to food chains. In addition, throu g h their activit y the y ma y prevent use of t he decaying material by other, pest insects, for example, flies. Perhaps of special interes t are t h e d ung b eet l es (Scara b ae id ae), most spec i es o f w hi c hb ury p i eces o ff res hd ung f or u se as egg- l ay i ng s i tes (F i gure 24.3). Genera ll y, t h e b eet l es are su ffi c i ent l ya b un d ant t h at a pat of fresh dun g ma y completel y disappear within a few hours, thus reducin g the numbe r of dun g -breedin g flies that can locate it. Furthermore, the chances of fl y e gg s or larvae survivin g within the dun g are ver y low because the dun g is g round into a fine paste as th e b eet l es or t h e i r l arvae f ee d .L ik ew i se, t h e surv i va l o f t h e eggs o f tapeworms, roun d worms, etc., present i nt h e d ung pro d ucer, i s severe l yre d uce db yt hi s act i v i ty . I n Australia there are an estimated 22 million cattle and 1 6 2 million sheep that collec- t ivel y produce 54 million tonnes of dun g (measured as dr y wei g ht) each y ear! The cattl e d un g especiall y provides food and shelter for man y insects, includin g the larvae of two fl y pests, t h e i ntro d uce db u ff a l o fl y ( Haemato b ia irritans exi g ua) i n no r the rn A ust r alia an d t h e nat i ve b us hfl y( M usca v etustissima) i n s out h eastern an d sout hw estern areas o f t he countr y . Furt h er, b ecause o f t h e g enera lly d r y c li mate, t h e d un g soon d r i es an d ma y rema in 7 34 CHAPTER 24 F I GU RE 24.3. (A) A dung beetle, S is y phus rubrus , with its ball of dung which is rolled away from the dung pa d an d t h en b ur i e d .T hi s sout h ern A f r i can spec i es was i ntro d uce di nto Austra li a i n 1973; an d (B) di agrammat i c sect i on t h rou gh nest o f t h e Austra li an nat i ve d un gb eet le Ont h op h agus compositus , w hi c h co l on i zes t h e d un g o f kangaroos, wallabies, and wombats. [A, photograph by J. Green. By permission of the Division of Entomology , C SIRO. B, f rom G. F. Bornem i ssza, 1971, A new var i ant o f t h e paracopr i c nest i ng type i nt h e Austra li an d ung b eet l e , Ont h op h agus compositu s , P e d o b io l ogi a 11 :1–10. B y perm i ss i on o f Gustav F i sc h er Ver l a g . ] [...]... (Tables 24. 4 and 24. 5) (See Chapter 16, Section 5.5 for a discussion TABLE 24. 4 Number of Species of Insects and Mites in Which Resistance to One or More Chemicals Has Been Documenteda Year 1908 1928 1938 1948 1954 1957 1960 1963 1965 1967 1975 1980 1984 1989 2003 a Species 1 5 7 14 25 76 137 157 185 224 364 428 447 504 536 Data from Georghiou and Taylor (1977), Metcalf (1989), Georghiou and Lagunes-Tejeda... thus relatively shortlived outside the host, are relatively slow-acting, have poor powers of dispersal, and are 757 INSECTS AND HUMANS 758 TABLE 24. 6 Examples of Successful Biological Control Projects Using Insects as Control Agentsa CHAPTER 24 Pest Primary control agentb and source Location and date of project Icerya purchasi (cottony-cushion scale) Rodolia cardinalis (vedalia beetle) (Australia)... the dissemination of insect parasites on humans and the diseases they carry Large-scale and long-term cultivation of the same crop over an area facilitated rapid population increases in certain plant-feeding species and the spread of plant diseases Modern transportation, too, encourages the spread of pest insects and insect-borne diseases Further, as described in Section 2.3, some of the attempts at pest... Lagunes-Tejeda (1991), and Resistant Arthropod Database (2004) 749 INSECTS AND HUMANS TABLE 24. 5 Number of Species of Arthropods with Reported Cases of Resistance Through 2003a 750 CHAPTER 24 Pesticide Groupb Importancec DDT Cyclod OCL OP Carb Pyr Fum Other Med./Vet Agr Benef Other Total Acari 14 Araneae Coleoptera 24 Copepoda Dermaptera 1 Dictyoptera 2 Diptera 129 Ephemeroptera 2 Hemiptera 7 Homopterans... chance of success The tactics are wide-ranging and include methods that affect the control agent either directly (e.g., providing it with alternate food sources and nest sites) or indirectly (e.g., adjusting 753 INSECTS AND HUMANS 754 CHAPTER 24 cultivation practices to improve the microclimate, increasing ecosystem diversity, and using insecticides that are non-persistent or benign to the control agent)... broad host-specificity 755 INSECTS AND HUMANS 756 CHAPTER 24 studies (Louda et al., 2003; Sheppard et al., 2003) For example, Cactoblastic cactorum, introduced so successfully into Australia for control of exotic Opuntia species (Section 2.3), was released on the Caribbean island of Nevis in 1957 as a control agent for native weedy Opuntia However, it was soon found on some of the rarer (non-weedy) Opuntia... 740 CHAPTER 24 T Transmission of human disease-causing microorganisms is not, however, entirely the domain of parasitic insects Many insects, especially flies, may act as mechanical vectors, contaminating human food as they rest or defecate on it, with pathogens picked up during contact with feces or other organic waste Examples of such insects and the diseases transmitted by them are listed in Table 24. 1... established, but assist in control of the pest to only a minor degree 759 INSECTS AND HUMANS 760 CHAPTER 24 active only in certain environmental conditions Added to these problems were technical difficulties that hampered research in this area, especially the inability to mass-produce microorganisms on a year-round basis for laboratory study as well as field trials This has been mainly overcome through... method of control is based on their position in the spectrum (Table 24. 3) At either end of the spectrum are the so-called “r pests” and “K pests,” with the “intermediate pests” in between The r pests are characterized by their potentially high rates of population increase (resulting from the high fecundity and short generation time), well-developed powers of dispersal (migration) and ability to locate... biological control, which is a relatively slow but long-term method, is of little use against r pests For such pests specific insecticides, which can be stored for application at short notice, continue to be the most important tool in their control Included in the r -pest group are the “classic” pests: locusts, aphids, mosquitoes, and house flies (Table 24. 3) K pests, on the other hand, have lower fecundity . Hence , at l ow h ost 7 30 CHAPTER 24 F I GU RE 24. 1. ( A ) C actoblastis cactorum caterpillars feeding on cactus pad; and cactus-infested pasture before (B) an d a f ter (C) re l ease o f C acto bl asti s . [ From. and C entra l A m e r ica B acter i a Stewart’ s b acterial w il t C or n C orn fl ea b eet le ( C haetocneme p ulicara ) ; toothed flea beetle ( C . d enticu l at a ) U SA C ucur bi tw il t Cucum b er , mus k me l on. Insects Whose Products Are C ommerc i ally Valuabl e The best-known insects in this category are the honey bee ( Apis mellifera ( ( ) , silkworm ( B ombyx mor i ), lac insect ( L acci f er lacc a ) ,