How does the "non-warning" plain-colored Euploea Sylvester larva (Nymphalidae, Danainae) defend itself?

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TThhee LLeepipdiopdteorpoltoegircaollSoocgieitycal Society ooff JJaapapnan
uttma Trans.Iqpid.Soc.Jtrpan 59 (2):103-106,March 2008

How does the "non-warning" plain-colore dEuploea sylvest learr'va
(NymphalidDaanea,inae)defenditself?

Haruo FuKuDA

Meiwa 4-5-32,Kagoshima, 890-O024japan

Abstract Although most larvae of danaine rnilkweed butterfii edsefend themselves by their warn-
ing coloration, the defenc estrategy of plain-colo rleadrva e(e .g. Euploea sylvester) has not been
noted. This paper describes some observations obtained in Taiwan on this topic, and discuss ehsow
the Euptoea sylvester larva defends itsel wfith its simple coloration.
Key words Danaine larva ,Euploea s),lvester, defenc esLrategy, inimicry, fallin gbehevior, warning
coLoration.
Introduction
Milkweed butterf llyarva e(Nymphlid Daaen,ainae) defend themselves by their warning col-
oration (aposemat iisn mas)sociation with storage ofpoisonous compounds from their food-
plant s(chemic daelfence) .Brower et al. (1992 )list sfive basic pigment coloration patterns
for the fift (hlas itn)sta lrarva eof Danainae :(1 )transvers estripes with or without spQts, (2)
only spotted, (3 )uniformly pale, (4 )longitudina lsltryiped, and (5 )transversel ystriped to-
gethe rwith a single ventral longitudin astlripe, appending the las tto the fbur pattern rsecog-
nized by Kitching (1985 )D.isregarding phylQgeny ,however, these may be regrouped into
four types: (1 )spotted type (e ,g. Ilarantic asita), (2 )striped type (e .g. 7)irumala limniace),
(3 )mixed type (e ,g. Danaus chr.x,sippus), and (4 )simple coloration (unifor mplalye )type
(i e.. Eupioea sylvester, E. midamus, and E. batesii) .The last type of larvae c,omprising
only three known species, are uniformly colored without warning speckles, Given this h,ow
do they defend themselves? This paper discusse tsheir defence strategy mainly based on
E. larvaeinTbiwan,
my observations made on sylvester
Defenee strategy of TWo-brand Crow Euploea sylvester larvae
On 24th April 2006, together with Mr Lee, I visited a habita tof E. syZveste rC,hunan
Seasid eForest Park, in Miaoli Prefecture ,northwestern [rhiwan .As this was in the prime
oviposition season for overwintered females, we found many eggs and young larvae on the
foodplan tG,ymnema sytvestre (Asclepiada cAelateh)ou.gh middle or las tinsta lrarva ewere
scarce, I fortunate lspyotted a fift ihnsta rlarva .No sooner had I stepped up to it to take a
photo ,than the larv aviolently shook it sbody and filaments and fe1 1into the bush under-
neath, I managed to take only a single photo of the larv abefOre it fe11 CFig 1.),
I had never seen such a hostil reeaction from a danaine larv ain response to what amounted
to on]y the slight sign of my approach. By contrast, taking photos of an ordinary danaine
larv ais usually easy eyen when it is alarmed. After this observatiQn in the wild, l repeated-
ly observed the same behavio rin captivity (Fi g2.). I have cencluded that thi sis protective
behavio rpeculiar to "non-warning" plain-color eddanaine larvae.
The defenc beehavio srequence of E. sylvester larva eis :(1 )hidin g when at rest, the 1arva
usually lie sin a hook-lik eposture c,oncealing it shead beneath the thorax; (2 )warning-
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104 Haruo FuKuDA

2.

Fig. 1. The las tjnsta rlarv aof E. s.}/lveste}' sitting on a dead vine of
the foodplan jtus btefor efall .After taking thi sphuto, it im-
mfedtiaptemlyt tfzi OfNell ,it lj C-C ue,IE t6 tc 'v a-t -iri O'i JlV ]J v N 7 ptwt
imM .t O !I LS m.'a re ftt <" l･ t:z ut L k.
Fig .2. A middle insta lrarv afalle nin a breeding case, violently shak-
ifnig ai tjt saE) n-t-c r-ior Vg p-a(i rtr zofB f Li] ･a,:m gen) wtst .WJ gl ,tt At crD 1ure digl ･LX <
etvllv(v6.

when frightene dt,he larv aviolently trembles itsbody and filarnen ftosr short period of
time; and (3 )falling-aft etrhe warning action, retaining the hook-likepaosture ,the ]arva
turns over on it sback and fa11s,
There has been no descripti oofn this peculiar defenc ebehavior, although 1arya eof the same
species (thou gmohst]y ditferi nign subspecies) have been recorded in [faiwan (Uchida,
19g8, 1991), India (Davids oetn at., 1869), Papua Ncw Guinea (Parso n1s9,99) ,and
Australja (Braby 2,000). As Ackery & Vane-Wright (1984 )reviewed and I also have often
observed, some danain elarva ecurl up and fal 1to the ground as a result of mild tactile stim-
ulation. However, I have never seen such violent fa11in bgehavio raccompanied with warn-
ing action as shown by E. sylvester, It is unique in two aspects: (1 )the larv ahas unusual
sensitivity to any slight stimulus, and (2 )after the violent waming action, it immediately
falls,
Discussion
The habi tof fa11i nags a defence strategy is common in many insect isncluding butterfi y1ar-
vae. For instanc ein butterfii gersa,ss feedin gcaterpillars ofArgyninae and Satyrinae easily
fal loff their fbodplant asnd often freez ewith their body curled up,
Falling behavior for defence is also seen for warning colored and shelter-making larvae.
The shelter-making larva of Lqptalin aunicolor (Hesperiid aweho)s,e coloration is probably
aposematic, actively tumbles out of it scylindrical cell of gras sleaf .In addition to these
gras sfeedin glarvae I, observed a similar behavior patter nshown by larva eof Badamia ex-
clamationis (Hesperii dreastein)g, in shelters madc of ]eave son a tal ltree, 7irrminati acat-
appa (Combretace iane G)u,am (th Meariana lsles) .When I cut a twig with some larval
shelters, the warning colored larva etumbled out of their shelters (Fukud a& Nicho, 2001).
The fallin gbehavior performed by the "non-warning;' plain-colore dlarv aof E, sylvester is
noteworthy, Most danain elarvae h,avin gaposematic coloratien, by contrast, do not easily
fa11 ,In addition to the non-aposematic body coloration, the E. sytvester 1arva embodies
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How does the "non-warning" plain-color Eeudptoea sylvester larv adefend itsel f? 105
such feature sas a slender cylindrical body shape and long rod-like tubercles (filaments),
Tubercle sof danaine larva eare assumed to be used for deterrin pgarasit e(sComstoc k&
Comstock, 1917, quoted in Ackery & Vtme-Wright ,1984) and for regulating bedy tempera-
ture (Bascomb eet al., 1999), though no experiment has been done to test these assump-
tiens ,In addition, the long slender body shape and long tubercles are probabl yusefu1 for
defendingthe 1arva.

Three importan tquestion sremain to be solved in the futur e(:1 )Defence behavio ris un-
known in any other congeneric species with larva ewith similarly simple coloration, i ,e, E.
midam"s in Hong Kong (Bascomb eet al., 1999) and PalavL,a nIsland (lgara s&h iFukuda,
2000) ,and E. batesi iin Papua New Guinea (Parson 1s9,99) .Do they have similar fa11ing
behavior ?(2 )Does the benefi tto the 1arv agained by fa11i ncgompensate fbr the risk of fail-
ing to retum to the foodplan tafter fa]ling ?(3 )Is the simple coloration of the 1arva usefu] as
waming?
Acknowledgments
The author wishes to thank Mr Hsin-Te Lee (Departm e&nt Graduate Institu toef
Entomology,NationalTletiwaUnniversityf)brhishelpinfieldworkinIbjwan,Dr Chien-

Chih Chen ([[ai pMueniicipal University of Education )and Dr YU-Feng Hsu (National
r[biwan Normal Universit yf)br their helpful adyice, Mr Kazuhiko Morishit a(Zushi-c fiotry)
his suggestions on danaine butterfli eansd, Dr Hiroyuki [Ibkasak i(Okayam aUniversit oyf
Science )for helpfu 1suggestions and critical reading of the manuscript.
References
Aekery,P.R.& R.I.Vane-Wright1.984.MilkweedButtenjlieBsri.tishMuseum (Naturhailstory).

Bascombe, M. J.,Johston,G. & F. S.Bascombe, 1999. T7ieButreiflieosfHong Kbng, Academic Press,

London.

Brower, L, P., Ivie ,M. A,, Fink, L. S., Watts, J, R &. R. A. Moranz, 1992, Life history ofAnetia briare aand
it sbearin gon the evolutionary re]ationships of the Danaina e(Lepidopt eNrymap;halidae) .Trop. Lepid.
3 (2) 6:4-73,
Braby, M. F., 2000 .Butteilfi ioesfAustralia- Jtdheenti(rficat iBioonl,ogy ,and Distributio n2. vii, 4S9-976
pp. CSIRO Publishing ,Collingwood VIC.
Davidson ,J .& E. H. Aitken, 1890, Notes on the larvae and pupae of some butterfii eosf the Bombay
Presidency. J. Bombay nat. Hist. Soc. 5: 260-278 ,349-375 ,6 pls ,(quot eidn Ackery & Vane-Wright,
1984),
Fukuda, H. & K. Nicho ,2001. Butterfi ireecsorded in 2000 and the succession of butterf flayuna in Guarn Is,,
the Mariana Isles .Butteig7i e(s30) 2:5-35 (i nJapanese).
IgarashiS,,& H.Fukuda,2000, T7ieL(feHistorieosfAsianButteij7iesV.ol.2. Tokai UniversityPress,

Tokyo.
Kitching, I .J. ,1985. Early stages and the classification of the milkweed butterfi i(eLscpidopt eDranaa:inae).
Zbol. J. Linn. Soc. 85: 1-97.
Parsons,M., 1999. IVieButteijTieosfPqpuaIVewGuinea. Academic Press,London.

Uchida ,H., 1988 .Amicts t'hte Lantanaflowers: B"tteifli eosfTZiiwan-NL{ tanudr eMan, 183 pp. Published
by the author, Japan. (I nJapanese).
, 1991 ,Charms ofFonnos aL,sland qfeverlastin gSummer: B"ttenj7i eosf7biwan-Nat aundr eMan.
216 pp. Puslished by the author, Japan ,(I nJapanese).
re g
v y7f g vxoff..utngkt uts kt"os s }c L(e&? ze t hli (w tva Heft)
-? yvf N v ,diil･os lg)l erkgk Lvli meau:s i os･ it ti:k a t abtk 6" it ,ue,ei, f.t&ececg eoEa
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lo6 Haruo FUKUDA

型に大別されるが，ル リマ ダラ属には 3例 〔ル リマ ダラ，ミダム スル リマ ダラ，バ テシ イル リマ ダラ）な
がら無紋で警告斑紋を持たない 幼虫がい る，で は彼らはいかに して身を守るのか．本報では台湾産ル リ
マ ダラの観察例を主に して この問題 を論ずる．
台湾の苗栗県竹南濱海森林公園における 2006年4月の 野外観察，およびその後の飼育時の観察に よ
る と，幼虫 （とくに中一終齢）の防衛行動は次の ようなもの である．（1）隠ぺ い 的行動 休息時，頭胸部を
釣針型に丸め，突起を倒 して静止 してい る．（2）威嚇的行動 もの に驚くと，体 と突起を激 しく震わせ
て威嚇する．（3）転落行動：威嚇の後，身体前半を内側に曲げたまま仰向けに反 り返るようにして して落
下する．
これらは多くのマ ダラチ ョ ウ類にも見られる もので はあるが，それ らの転落は強い接触刺激を受けた
時であり，幼虫のこれほ ど激しい威嚇行動はない ．しかるに，本種は人が撮影に近づい ただけで何ら
かの刺激を感知し，激 しく威嚇した後すぐに転落した点が特徴的である，これには単色で細長い体形と
長い 突起とい う形態的特徴と深く関わっ てい る可能性が高い ，もちろん，単なる転落行動なら草食性幼
虫の ほか造巣性幼虫で もみ られ，警告色斑紋の幼虫にもみ られるもの であるが，ル リマ ダラ属の中で少
数種の みが，なぜ この ような戦術をとるの か興味深く，本格的な調査が期待される．
（Accepted　October　22，2007）
Publishe　dby　the　Lepidopterolog］iScoaCiety　of　Japan，
5−20，Motoyokoyama2，Hachioj，Tokyo，192−0063 Japall

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