Body weight as related to wing measure in hawkmoths (Sphingidae)

2 Pages·1997·0.94 MB·English

by  William F Miller

GENERAL NOTES
JournaloftheLepidopterists'Society
51(1), 1997,91-92
BODYWEIGHTAS RELATEDTOWING MEASURE IN
HAWKMOTHS (SPHINGIDAE)
Forewingorhindwinglength(L)andforewingspan(S)areoftenusedasspeciesbody-
sizeindicesin Lepidoptera,butthebodyweights (W) actuallyrepresentedarenotusually
known. Establishing mathematical relations between totalbodyweight or mass andwing
measure among species ofataxon not onlyvalidates the use ofwing measure as abody
size surrogate (Miller 1996), but also enables estimation ofbodyweight from wing mea-
sureforphysiologicalandecologicalpurposes. Indetail, suchrelationsWarespecificfordif-
ferentgroups; in form, theyare usuallyallometricpowerfunctions of = a (Lbor Sb) or
the logarithmic equivalent (Miller 1977). Winglength is defined here as the distance be-
tween the wing base (excluding tegula) and the farthest extending wing tip (including
fringe);wingspanis definedas the farthestdistancebetweenthewingtips on specimens
spreadinthe usual manner.
IntheirstudiesoffliWghtmechanics, BartholomewandCasey(1978) andCasey(1976) as-
sembledandtabulated and Lvalues for 15 and38ideWntifiedhawkmoth species, respec-
tively. Although theydid not derive relations between and L in the foregWoingpapers,
Casey (1989) presented such a relationlater. This relation had L ratherthan as thede-
pendentvariable,wasbasedononlythesmalleroftheabovedatasets,andwasdisplayedon
Live body wt.
(W)
(g)
W 206
6.0 = 0.000548 (L )
Raw r 2 = 0.90
° Macroglossinae
• Sphinginae
4.0
2.0 "
^P*"
0.0
20 40 60 80 100
Forewing length (mm) (L)
FlG. 1. Livebodyweightas relatedto forewinglengthinhawkmoths. Eachpointrep-
resents from one to several individuals ofeither or both sexes ofa species. Data from
BartholomewandCasey(1978) andCasey(1976).
—
92 Journal of the Lepidopterists' Society
W
adouble-logarithmicscale. HereIrecharacterizetherelationwith asthedependentvari-
ableusingbothoftheabovedatasetsanddisplayingresultsonanarithmeticscale.
Study data here are 70 observations on live weight (W), forewing length (L), and
forewing span (S) offield-caught individuals of48 identified species (Bartholomew &
Casey 1978, Casey 1976). These species include 33 Macroglossinae and 15 Sp—hinginae
the sole subfamilies recognized in Sphingidae (Hodges 1971, Pittaway 1993) andthere
are29 NewWorldand 19OldWorldspecies.Thesexesarepooledbecausemanyindivid-
uals originallywere not sexed. Species liveweights range from 0.18 to 6.25 g, essentially
the full range forthe family. Fordisplay, two or more observations forthe same species
were averaged. In analysis, species meanswereweightedbythe numberofobservations.
Where only S was originallygiven fora species, as in the data set ofCasey (1976), I de-
rived Laftermeasuring L and S on D'AbreWra's (1986) life-size illustrations such that L =
S(LD-Abrera/SD-Abrera). Tosolvethe equation = a (Lb), I usedthe quasi-Newtonloss func-
tionforordinaryleast-squaresnonlinearregression (SYSTAT 1992). Iderivedproportion-
alityfunctions forinterconverting Land S bysimpleordinaryleast-squares regression.
The recharWacterized family-level relation between live bodyweight (W) and forewing
length (L) is = 0.000548 (L206) (Fig. 1). Itis evidentfrom Fig. 1 thatsample speciesof
SphinginaearelargerinmeansizethanthoseofMacroglossinae, anoutcomethatmayrWe-
flect areal condition amonghawkmoths. The subfamilies do not seem to differin the
versus L relation, however. Theproportionalityfunctionswhich servetoestimate Lfrom
Sandviceversawhenoneortheothermeasurementisavailablebuttheotherdesiredare
L = -1.09 + 0.467 S, and S = 4.46 + 2.094 L (r2= 0.98).
Thisstudyreconfirmsthathawkmothbodyweightisindexedbywingmeasure. Livebody
weightincreasesasthesquareofforewinglengthin Sphingidae,whereasitincreasesasthe
cubeinTortricidae (Miller 1977). The differenceis fundamental, andreflects theempirical
natureofsuch relations andtheirdependenceon morphometries andphysiology
Liveweights estimated from the nonlinearequationwith forewinglength (Fig. 1) are
not intended for rigorous use. Rigorous usewould require not onlyconfidence intervals
forthe equation, but also body-weight controls in the original sources for sex, eggload,
andcropcontent.
I thank L. S. Fink, T. M. Caseyand an anonymous readerforuseful reviewcomments
onthe manuscript.
Literature Cited
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William E. Miller, Entomology Department, University ofMinnesota, Saint Paul,
Minnesota 55108, USA.
Receivedforpublication 10May 1995; revisedandaccepted6January 1996.