darwin and modern science-第89节

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collection；　and　cannot　therefore　be　precisely　identified；　he　wrote：　　〃Cimex。。。Nature　seems　to　have　intended　it　to　imitate　a　Sphex；　both　in　colour　and　the　rapid　palpitating　and　movement　of　the　antennae〃　（November　15；　1826）。　　At　the　same　time　it　is　impossible　not　to　feel　the　conviction　that　Burchell　felt　the　advantage　of　a　likeness　to　stinging　insects　and　to　aggressive　ants；　just　as　he　recognised　the　benefits　conferred　on　desert　plants　by　spines　and　by　concealment。　　Such　an　interpretation　of　mimicry　was　perfectly　consistent　with　the　theological　doctrines　of　his　day。　　（See　Kirby　and　Spence；　〃An　Introduction　to　Entomology〃　（1st　edition）；　London；　Vol。　II。　1817；　page　223。）

The　last　note　I　have　selected　from　Burchell's　manuscript　refers　to　one　of　the　chief　mimics　of　the　highly　protected　Lycid　beetles。　　The　whole　assemblage　of　African　insects　with　a　Lycoid　colouring　forms　a　most　important　combination　and　one　which　has　an　interesting　bearing　upon　the　theories　of　Bates　and　Fritz　Muller。　　This　most　wonderful　set　of　mimetic　forms；　described　in　1902　by　Guy　A。K。　Marshall；　is　composed　of　flower…　haunting　beetles　belonging　to　the　family　Lycidae；　and　the　heterogeneous　group　of　varied　insects　which　mimic　their　conspicuous　and　simple　scheme　of　colouring。　　The　Lycid　beetles；　forming　the　centre　or　〃models〃　of　the　whole　company；　are　orange…brown　in　front　for　about　two…thirds　of　the　exposed　surface；　black　behind　for　the　remaining　third。　　They　are　undoubtedly　protected　by　qualities　which　make　them　excessively　unpalatable　to　the　bulk　of　insect…eating　animals。　　Some　experimental　proof　of　this　has　been　obtained　by　Mr　Guy　Marshall。　　What　are　the　forms　which　surround　them？　　According　to　the　hypothesis　of　Bates　they　would　be；　at　any　rate　mainly；　palatable　hard…pressed　insects　which　only　hold　their　own　in　the　struggle　for　life　by　a　fraudulent　imitation　of　the　trade…mark　of　the　successful　and　powerful　Lycidae。　　According　to　Fritz　Muller's　hypothesis　we　should　expect　that　the　mimickers　would　be　highly　protected；　successful　and　abundant　species；　which　（metaphorically　speaking）　have　found　it　to　their　advantage　to　possess　an　advertisement；　a　danger…signal；　in　common　with　each　other；　and　in　common　with　the　beetles　in　the　centre　of　the　group。

How　far　does　the　constitution　of　this　wonderful　combinationthe　largest　and　most　complicated　as　yet　known　in　all　the　worldconvey　to　us　the　idea　of　mimicry　working　along　the　lines　supposed　by　Bates　or　those　suggested　by　Muller？　　Figures　1　to　52　of　Mr　Marshall's　coloured　plate　（〃Trans。　Ent。　Soc。　Lond。〃　1902；　plate　XVIII。　　See　also　page　517；　where　the　group　is　analysed。）　represent　a　set　of　forty…two　or　forty…three　species　or　forms　of　insects　captured　in　Mashonaland；　and　all　except　two　in　the　neighbourhood　of　Salisbury。　　The　combination　includes　six　species　of　Lycidae；　nine　beetles　of　five　groups　all　specially　protected　by　nauseous　qualities；　Telephoridae；　Melyridae；　Phytophaga；　Lagriidae；　Cantharidae；　six　Longicorn　beetles；　one　Coprid　beetle；　eight　stinging　Hymenoptera；　three　or　four　parasitic　Hymenoptera　（Braconidae；　a　group　much　mimicked　and　shown　by　some　experiments　to　be　distasteful）；　five　bugs　（Hemiptera；　a　largely　unpalatable　group）；　three　moths　（Arctiidae　and　Zygaenidae；　distasteful　families）；　one　fly。　　In　fact　the　whole　combination；　except　perhaps　one　Phytophagous；　one　Coprid　and　the　Longicorn　beetles；　and　the　fly；　fall　under　the　hypothesis　of　Muller　and　not　under　that　of　Bates。　　And　it　is　very　doubtful　whether　these　exceptions　will　be　sustained：　　indeed　the　suspicion　of　unpalatability　already　besets　the　Longicorns　and　is　always　on　the　heels；I　should　say　the　hind　tarsiof　a　Phytophagous　beetle。

This　most　remarkable　group　which　illustrates　so　well　the　problem　of　mimicry　and　the　alternative　hypotheses　proposed　for　its　solution；　was；　as　I　have　said；　first　described　in　1902。　　Among　the　most　perfect　of　the　mimetic　resemblances　in　it　is　that　between　the　Longicorn　beetle；　Amphidesmus　analis；　and　the　Lycidae。　　It　was　with　the　utmost　astonishment　and　pleasure　that　I　found　this　very　resemblance　had　almost　certainly　been　observed　by　Burchell。　　A　specimen　of　the　Amphidesmus　exists　in　his　collection　and　it　bears　〃651。〃　　Turning　to　the　same　number　in　the　African　Catalogue　we　find　that　the　beetle　is　correctly　placed　among　the　Longicorns；　that　it　was　captured　at　Uitenhage　on　Nov。　18；　1813；　and　that　it　was　found　associated　with　Lycid　beetles　in　flowers　（〃consocians　cum　Lycis　78…87　in　floribus〃）。　　Looking　up　Nos。　78…87　in　the　collection　and　catalogue；　three　species　of　Lycidae　are　found；　all　captured　on　Nov。　18；　1813；　at　Uitenhage。　　Burchell　recognised　the　wide　difference　in　affinity；　shown　by　the　distance　between　the　respective　numbers；　for　his　catalogue　is　arranged　to　represent　relationships。　　He　observed；　what　students　of　mimicry　are　only　just　beginning　to　note　and　record；　the　coincidence　between　model　and　mimic　in　time　and　space　and　in　habits。　　We　are　justified　in　concluding　that　he　observed　the　close　superficial　likeness　although　he　does　not　in　this　case　expressly　allude　to　it。

One　of　the　most　interesting　among　the　early　observations　of　superficial　resemblance　between　forms　remote　in　the　scale　of　classification　was　made　by　Darwin　himself；　as　described　in　the　following　passage　from　his　letter　to　Henslow；　written　from　Monte　Video；　Aug。　15；　1832：　　〃Amongst　the　lower　animals　nothing　has　so　much　interested　me　as　finding　two　species　of　elegantly　coloured　true　Planaria　inhabiting　the　dewy　forest！　　The　false　relation　they　bear　to　snails　is　the　most　extraordinary　thing　of　the　kind　I　have　ever　seen。〃　　（〃More　Letters〃；　I。　page　9。）

Many　years　later；　in　1867；　he　wrote　to　Fritz　Muller　suggesting　that　the　resemblance　of　a　soberly　coloured　British　Planarian　to　a　slug　might　be　due　to　mimicry。　　（〃Life　and　Letters〃；　III。　page　71。）

The　most　interesting　copy　of　Bates's　classical　memoir　on　Mimicry　（〃Contributions　to　an　Insect　Fauna　of　the　Amazon　Valley〃。　　〃Trans。　Linn。　Soc。〃　　Vol。　XXIII。　1862；　page　495。）；　read　before　the　Linnean　Society　in　1861；　is　that　given　by　him　to　the　man　who　has　done　most　to　support　and　extend　the　theory。　　My　kind　friend　has　given　that　copy　to　me；　it　bears　the　inscription：

〃Mr　A。R。　Wallace　from　his　old　travelling　companion　the　Author。〃

Only　a　year　and　a　half　after　the　publication　of　the　〃Origin〃；　we　find　that　Darwin　wrote　to　Bates　on　the　subject　which　was　to　provide　such　striking　evidence　of　the　truth　of　Natural　Selection：　　〃I　am　glad　to　hear　that　you　have　specially　attended　to　'mimetic'　analogiesa　most　curious　subject；　I　hope　you　publish　on　it。　　I　have　for　a　long　time　wished　to　know　whether　what　Dr　Collingwood　asserts　is　truethat　the　most　striking　cases　generally　occur　between　insects　inhabiting　the　same　country。〃　　（The　letter　is　dated　April　4；　1861。　　〃More　Letters〃；　I。　page　183。）

The　next　letter；　written　about　six　months　later；　reveals　the　remarkable　fact　that　the　illustrious　naturalist　who　had　anticipated　Edward　Forbes　in　the　explanation　of　arctic　forms　on　alpine　heights　（〃I　was　forestalled　in　only　one　important　point；　which　my　vanity　has　always　made　me　regret；　namely；　the　explanation　by　means　of　the　Glacial　period　of　the　presence　of　the　same　species　of　plants　and　of　some　few　animals　on　distant　mountain　summits　and　in　the　arctic　regions。　　This　view　pleased　me　so　much　that　I　wrote　it　out　in　extenso；　and　I　believe　that　it　was　read　by　Hooker　some　years　before　E。　Forbes　published　his　celebrated　memoir　on　the　subject。　　In　the　very　few　points　in　which　we　differed；　I　still　think　that　I　was　in　the　right。　　I　have　never；　of　course；　alluded　in　print　to　my　having　independently　worked　out　this　view。〃　　〃Autobiography；　Life　and　Letters〃；　I。　page　88。）；　had　also　anticipated　H。W。　Bates　in　the　theory　of　Mimicry：　　〃What　a　capital　paper　yours　will　be　on　mimetic　resemblances！　　You　will　make　quite　a　new　subject　of　it。　　I　had　thought　of　such　cases　as　a　difficulty；　and　once；　when　corresponding　with　Dr　Collingwood；　I　thought　of　your　explanation；　but　I　drove　it　from　my　mind；　for　I　felt　that　I　had　not　knowledge　to　judge　one　way　or　the　other。〃　　（The　letter　is　dated　Sept。　25；　1861：　　〃More　Letters〃；　I。　page　197。）

Bates　read　his　paper　before　the　Linnean　Society；　Nov。　21；　1861；　and　Darwin's　impressions　on　hearing　it　were　conveyed　in　a　letter　to　the　author　dated　Dec。　3：　　〃Under　a　general　point　of　view；　I　am　quite　convinced　（Hooker　and　Huxley　took　the　same　view　some　months　ago）　that　a　philosophic　view　of　nature　can　solely　be　driven　into　naturalists　by　treating　special　subjects　as　you　have　done。　　Under　a　special　point　of　view；　I　think　you　have　solved　one　of　the　most　perplexing　problems　which　could　be　given　to　solve。〃　　（〃Life　and　Letters〃；　II。　page　378。）　　The　memoir　appeared　in　the　following　year；　and　after　reading　it　Darwin　wrote　as　follows；　Nov。　20；　1862：　　〃。。。In　my　opinion　it　is　one　of　the　most　remarkable　and　admirable　papers　I　ever　read　in　my　life。。。I　am　rejoiced　that　I　passed　over　the　whole　subject　in　the　〃Origin〃；　for　I　should　have　made　a　precious　mess　of　it。　　You　have　most　clearly　stated　and　solved　a　wonderful　problem。。。Your　paper　is　too　good　to　be　largely　appreciated　by　the　mob　of　naturalists　without　souls；　but；　rely　on　it；　that　it　will　have　LASTING　value；　and　I　cordially　congratulate　you　on　your　first　great　work。　　You　will　find；　I　should　thin