Some Observations of a Saunders Case Moth 'Metura elongatus' Larva

2011·0.74 MB·English

by  Virgil Hubregtse

NaturalistNote
Some observations ofa
Saunders Case Moth Metura elongatus larva
Introduction
Saunders Case Moth Metura elongatus is a pillar was protruding from the other end (Fig.
memberofthefamilyPsychidae,ofwhichthere 1). Thecreaturewas motionlessand apparently
are about 350 species in Australia (Zborowski had drowned. 1 put the case with its unfortu-
and Storey 2003). In the caterpillar stage, this nate occupant on asheetofcardboard thatwas
insect usescaterpillarsilktoconstructanelon- lying on the table, and emptied the bucket to
gate, spindle-shaped case, to which it attaches preventanyfurthermishap.At5.00pmthecase
short lengths ofslender twigs at widely spaced was still on the table, but the caterpillar’s rear
intervals. The front part of the caterpillar is end was nolongervisible.
orangeand black, while the rearpart iscream- Subsequentmovements
coloured. Before pupation, the caterpillar at- Thefollowingmorningat8.00amthecase,now
taches its case to a secure support by a tough dry, had moved and was firmly attached to the
band ofsilk, then turns around inside the case edgeofthetablewithcaterpillarsilk(Fig.2). By
andpupatesheaddownwards.Ifitisamale,the 1.00 pm the case had moved again. The orange
moth emerges the following spring; if female, andblackheadendofthecaterpillarwasvisible
the insect is a wingless, grub-like creature that as the creature moved slowly along the edge
atrmhenaemdkaemiwanlhtsehei,isnnwphttoihhsecseihcblalhaserae.,vsaEweaghngehsraexteatcrehesnhsleitalhiieedsyafiebnurdtstieohlmiesseeicndlaksbeteyno, polalftaetcrheesdatiwatbiultencdl(eiFrimgb.tihn3e)g.BuaApnfktoesnrieapohsfpoittnhoueglrborsaaap,nhciwhnheges.rite, I1
threadstolowerthemselvesontofoliagebefore
constructingconical silkencapsforprotection.
(Common 1990; McKeown 1944; Zborowski
and Storey2003). Fig. 1. Wet case
Under normal circumstances, the rear end with rear end of
caterpillar protrud-
ofthelarva is not seenbecauseit is kept inside ing.
the case at all times (Coffs Harbour Butterfly
House web site). This note gives an account of
acircumstance inwhich the rearend ofa larva
protruded from its case, and of subsequent
events.
Apparentdrowning
At 10.45 am on 21 March 2010, I saw a Saun-
dersCaseMothcaselyingontheconcretenear
a dwarf Banksia spinulosa at the back of our
house. I picked upthecaseand put itonanold
tableoutsidethebackdoor, intendingtoexam-
ineitlater.Thecasefeltverylight.Theheadend
was wide open, and I expected the case to be
empty.
At about 3.00 pm I found the case in a buck-
et of‘grey’ water that was under the table: no
doubt thecasehadbeen carriedtherebyagust
ofwind. I don’t know how long it had been in
thewater, butthecasewasverywetand mostly Pi
submerged. The previouslyopen head end was
closed, and the pale rear section of the cater-
TheVictorianNaturalist
90
NaturalistNote
On 28 March I discovered that the caterpil- by no means certain because these caterpillars
larhadclimbed apole ofthepatio close to the are frequently parasitised by flies and wasps
Banksia. I watched it proceed up to the laserl- (Brewsteretal. 1920).Acasecontainingalarva
iteroof, whereitlostitsgrip andfell off. Again that diedbefore completingpupation is shown
theheadendofthecasewasopen, andthecat- in the lower figure on the back cover. In this
erpillar was not visible, so I suppose this was instancethecauseofdeathisnotknown.
a repeat of what had happened before I first The only other Saunders Case Moth larva I
found it. On 29 March the caterpillar, possibly haveseen in ourgardenwashereinJune 1992,
exhaustedfromits ordeal, nextoptedto secure alsonearourdwarfBanksiaspinulosa.
itselfin a position about halfway up the pole.
References
It remained there for eight months, emerg- BrewsterMN,BrewsterAAandCrouchN(1920)Lifestories
ing as an adult male moth on the night of30 ofAustralianinsects.(DymocksBookArcade:Sydney)
November. CofFs Harbour Butterfly House web site http://Iepidoptera.
butterflyhouse.com.au/psyc/elong.html
Discussion Common, IFB (1990) MothsofAustralia. (MelbourneUni-
versityPress:Melbourne)
Thecaseinwater McKeown KC (1944) Australian insects: an introductory
I wondered how the caterpillar had managed handbook. (RoyalZoologicalSocietyofNewSouthWales:
Sydney)
to survive in the water. Ian Endersby (pers. QueenslandMuseum factsheets web sitewww.qm.qld.gov.
cspoimramc.le)s.suIgdgoens’ttedknthoawthitowwoullodnghaavneicnlseocstedcaitns ZbAaouurs/otirwnasqlkiuiai.rPy2/nafdnadcetdSsnth.oere(etRyse/eRcda(Ns2ee0_0wm3o)HtohAlsl_fa2ine0dl0d:8g0Su7yi0dd9n.eepytd)ofinsectsin
dothisbeforeithastobreathe. Perhapsthecat-
erpillar used its rear end to block the opening
inthecaseandpreventwaterfromentering? VirgilHubregtse
6SanikyStreet
Sizeofthecase NottingHill,Victoria3168
CasesoffemaleSaunders CaseMothsare 12 to
15 cm long (Queensland Museum fact sheets
web site), and are larger than those of males.
This case was 9.5 cm long, not counting the
length ofthe sticks. A part ofthe abandoned
case is shown in the upper figure on the back
cover. This creature was fortunate; success is
Fig.2.Caseattachedtotablewithcaterpillarsilk. Fig.3.Larvamovingalongedgeoftable.
Voll28 (2) 2011 91
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