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Journal of

HE LEPIDOPTERISTS' SOCIETY

Volume 53                                                                        2000                                                                     Number 4

Journal of the Lepidopterists' Society 53(4), 1999, 133-137

DISTRIBUTION AND HOSTPLANT RECORDS FOR EUPACKARDIA CALLETA FROM SOUTHEASTERN TEXAS WITH NOTES ON MANDIBULAR MORPHOLOGY OF

ATTACINI (SATURNIIDAE)

Valerie A. Passoa

10603 Brettridge Drive, Powell, Ohio 43065, USA AND

Steven Passoa1

USDA/APHIS/PPQ, The Ohio State University, Museum of Biological Diversity, 1315 Kinnear Road, Columbus, Ohio 43212, USA

ABSTRACT. Eupackardia calleta (Westwood) is recorded on privet (Ligustrum) from Kingwood, Texas. This new county record represents a northeastern range extension of 100 miles and confirms privet as a hostplant under natural conditions. The role of the mandible in digestion of the hostplant is discussed.

The last instar larval mandible of most Attacini either lacks teeth or has the cutting edge bluntly serrated with reduced teeth. In contrast, the distinctive mandible of E. calleta contains three large teeth and deep molar ridges, an autapomorphy for the genus. Well-developed mandibular teeth are present on the last instar of a few unrelated Saturniinae and Ceratocampinae; therefore this character is homoplastic in Saturniidae. A structurally complex mandible of the "sphingid-type" occurs in several saturniids such as Antheraea pernyi (Guer.- Men.) (Saturniidae). This mandible type is illustrated.

There are two ontogenetic patterns of mandibular development in Saturniidae. In one case, teeth are present in the first instar, then lost in later molts. The mandibular development of E. calleta represents an alternative scenario where teeth are present throughout the larval stage.

Additional key words: Ligustrum, ontogenetic development, Sphingidae, Notodontidae.

Eupackardia calleta (Westwood) is a member of the Attacini, usually considered the sister group to Roth-schildia (Ferguson 1972, Peigler 1989, Friedlander et al. 1998). This species is distributed from Central America (Honduras, Guatemala) north to Arizona and southern Texas (Victoria Co., Calhoun Co.) (Ferguson 1972, Wolfe 1995, Tuskes et al. 1996). The systematics and biology of E. calleta have been reviewed by several authors including Ferguson (1972), Weast (1989), Miller (1976), Lemaire (1978), and Tuskes et al. (1996).

Weast (1989) suggested that systematic studies of E. calleta are needed. Tuskes et al. (1996) illustrated three larval forms of the United States populations, but did not study their mandibular morphology. In this paper we present biological data on E. calleta from southeastern Texas, then compare the mandibular

1 Address correspondence to this author

morphology to other Attacini, with emphasis on related nearctic taxa. Ontogenetic and phylogenetic observations are also included.

Materials and Methods

In order to survey saturniid mandibles, preserved larval specimens or exuviae associated with cocoons and emerged adults were taken from the authors' collection and dissected. The mandible was either slide mounted in Euperal or preserved in alcohol. For analysis with a J.O.E.L. JSM 820 scanning electron microscope, each sample was attached to a stub with carbon paint and coated with a thin conductive layer of gold-palladium. Mandibular terminology is based on Godfrey (1972).

Material examined: Eupackardia calleta: TEXAS (various localities, ex ova from female moths in lab culture): 10 eggs, 10 first ins tars, 27 second to fourth in-

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Table 1. Mandibular morphology of selected late instar Attacini larvae occurring in the Western Hemisphere. Locality data designate source of the study specimens.

bluntly serrate

stars, 6 pupal cases (with larval exuviae), det. V. A. Pas-soa, mandible slides #581, 582 S. Passoa collection; Harris Co., Kingwood, XII-1995, on Ligustrum, V. A. Passoa, 6 mature larvae, det. V. A. and S. Passoa, mandible slide # 616 S. Passoa coll.

MEXICO: various localities, collection data unknown, 2 first instars, 18 second to fourth instars, 3 pupal cases (with larval exuviae), det. V. A. Passoa; Mich. [Michoacan], Urupan (sic) [Uruapan], 2-X-1941, coll. [D. M.] Delong, det. V. A. and S. Passoa (1 last instar larva with mandibles slide mounted (The Ohio State University collection).

One to ten mandibular pairs of each species (Table 1) were examined, depending on material available.

RESULTS AND DISCUSSION

During November 1995, the senior author collected seven third instar larvae of E. calleta on privet (Ligus-trum) from her backyard in Kingwood, Harris Co., Texas. This is a northeastern range extension of approximately 100 miles (161 km) and a new county record. It remains to be determined if E. calleta is now established in Harris County.

Tuskes et al (1996) considered Leucophyllum frutescens (ceniza, purple sage) to be the main host-plant for E. calleta in Texas. Privet is normally treated

as an artificial laboratory host (Ferguson 1972,Tuskes et al. 1996). Ours is the second published record for E. calleta eating ornamental privet under natural conditions, supporting the suggestion of Weast (1989) that privet is an important hostplant of this species near urban areas of Texas. In fact, E. calleta appears to be oligophagous on several genera of Oleaceae, including privet in Texas (present study) and Mexico (Peigler pers. comm.), Fraxinus greggii A. Gray in western Texas (Peigler pers. comm.), and Forestiera angustifo-lia Torrey (Stone 1991). A mature larva of E . calleta on privet from Kingwood, Texas, is illustrated in Fig. 1. At maturity, the larva lacks long and dark scoli which are characteristic of earlier instars (Fig. 2). In spite of the availability of ceniza nearby, E. calleta was found only on privet in the senior author s backyard.

Examination of E. calleta mandibles from Texas showed that these structures are atypical compared to other saturniids described in the literature. Bernays and Janzen (1988) characterized late instar saturniid mandibles as "short, with a broad base, and without obvious teeth". This definition does not fit E. calleta which has large teeth in both the early (Fig. 3) and last instars (Figs. 4, 5, and 6).

Except for E. calleta, members of the Attacini typically lack well-developed mandibular teeth in the last instar or have the cutting edge of the mandible serrated with blunt lobes (Table 1). Mandibular teeth are also absent in mature larvae of two Indo-Australian Attacini, Attacus atlas (L.) (Heppner et al. 1989) and Coscinocera hercules (Miskin) (specimens in Passoa collection).

Our data on saturniid mandibles agree with results of a survey of notodontid mandibles published by Godfrey et al. (1989) in several respects. Last instar mandibles of the Notodontidae usually lack teeth, except for a few apparently unrelated exceptions. This is also true in Saturniidae. Outside of the Attacini, mature larvae of Actias selene (Hbn.), A. luna (L.), Argema mittrei (Guer.- Men.) (Saturni-inae) and Citheronia re galls (F.) (Ceratocampinae) (specimens in Passoa collection) have well-developed mandibular teeth, so the presence of teeth on saturniid mandibles is homoplastic across several subfamilies.

Large teeth also occur in the Antheraea genus complex, for example, Antheraea pernyi (Guer.- Men.) and its purported synonym A. hartii (Moore), A. polyphenols (Cram.), and Opodiphthera eucalypti (Scott) (spms. in Passoa coll.). In addition, the mandible of A. pernyi is unusual because it matches the "sphingid-type" as defined by Bernays and Janzen (1988). Sphin-gid mandibles were characterized as being "ridged in a

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Figs. 1-3. Eupackardia calleta (Westwood) from Texas. 1, late instar larva on privet (lateral view). 2, mid-instar larva on privet (dorsal view). 3, early instar mandible, oral surface, ventral view, photographs under polarized light, lOOx.

Figs. 4-6. Mandible of last instar Eupackardia calleta (West-wood), scale line = .10 mm in all figures. 4, oral surface, ventral view, 70x. 5, teeth and deep molar ridges, ventral view, 150x. 6, teeth on cutting margin, dorsal view, 95x.

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FlGS. 7-9. Mandible of last instar Antheraea pernyi (Guer.-Men.). 7, complex pattern of teeth on dorsal and oral surfaces, ventral view, 27x, scale line = 1 mm. 8, overlapping teeth of dorsal surface, ventral view, 33x, scale line = 1 mm. 9, tooth of dorsal surface, ventral view, 70x, scale line = .1 mm.

Journal of the Lepidopterists' Society

variety of complex ways". The mandible of A. pernyi (Figs. 7, 8, and 9) has a series of complex ridges on the dorsal surface that appear to form overlapping teeth, in addition to several smaller toothlike projections on the oral surface. The mandibles of E. calleta and A. pernyi suggest it is wiser to characterize saturniid mouthparts with ecological or physiological criteria (cutting versus grinding), instead of using a phylogenetic approach at the family level as did Bernays and Janzen (1988) in their study of saturniid and sphingid mandibles.

There appear to be two ontogenetic patterns for saturniid mandibles. In one pattern, first instar larval mandibles have teeth; subsequently these teeth are lost in later molts. This pattern is typical for Costa Ri-can saturniid species in four subfamilies (Bernays & Janzen 1988). A second pattern is found in E. calleta where early instars have mandibular teeth (Fig. 3) that are retained throughout larval life (Figs. 4, 5, and 6). This dichotomy was also noted by Godfrey et al. (1989) in notodontid genera.

Godfrey et al. (1989) stated that characterization of certain taxa by mandibular morphology was "problematical" because in some species the mandibular margin was intermediate between toothed and smooth. Intermediate conditions are common with Saturniidae, as shown in Table 1 by the term "margin bluntly serrate". A bluntly serrated mandible has round conical projections that resemble small teeth, or an irregular mandibular margin with indentations. Callosamia is an example of the first condition where from 10-15 small teeth cover the cutting margin of the mandible.

Irregular mandibular margins are found in Hyalo-phora and Rothschildia where it is difficult to discern teeth, but the mandibular margin is not straight. Dock-ter (1993) warned that mandibular wear must be taken into account when describing mandibles. It is unclear whether bluntly serrated teeth in Saturniidae are a transition state between toothed and smooth mandibles, as noted by Godfrey et al. (1989) in notodontids, or instead represent worn mandibular teeth as described by Dockter (1993) in Heterocampa and Soura-kov (1996) in larvae of satyrid butterflies. Examination of unworn mandibles on freshly molted larvae are needed to resolve this question. Thus, it may be premature to characterize saturniid mandibles as usually toothless (Bernays & Janzen 1988) until more ontogenetic studies are published.

In summary, the mandibular shape of Macrolepi-doptera depends on several factors including head size and food toughness (Bernays 1986), food particle size and chemistry (Bernays & Janzen 1988), the need to pierce the chorion of the egg at eclosion, and a need to

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seal die oral cavity during ingestion (Godfrey et al. 1989). Unlike notodontids which use toothed mandibles to pierce the leaf epidermis (Dockter 1993), E. collet a does not skeletonize leaves during any ins tar (V. A. Passoa pers. obs.). Therefore, it seems likely that a toothed mandible is required for other reasons.

Bernays and Janzen (1988) noted that larvae which feed on toxic plants tend to be associated with mandibles that contain teeth. They (Bernays & Janzen 1988) suggested that complete mastication of the leaf tissue allows more complete digestion, a strategy not possible with hostplants containing tannins that inhibit digestive efficiency However, the digestive physiology of E. calleta may be more complicated than other Sat-urniidae. Caterpillars of E. calleta secrete a pungent liquid containing phenolic compounds and biogenic amines from their scoli when disturbed, but it is unknown if plant toxins are sequestered for this secretion (Demi & Dettner 1993). Until the metabolism and defensive chemistry of E. calleta are clarified, it may be premature to assume mandibular teeth are an aid to coping with plant toxins. Nevertheless, E. calleta larvae do utilize toxic plants (Weast 1989).

Besides the need to understand mandibular morphology in an ecological context, it should be noted that a survey of saturniid mandibles would aid identification of the immatures. Minet (1994:70) mentioned mandibular secondary setae as an apomorphy of the Lasiocampidae, although these setae are also independently evolved in other macrolepidopteran families. Mandibular secondary setae are present (Agapema) or absent (E. calleta) in Saturniidae, thus this character has potential for identification purposes. Mandibular teeth associated with the cast larval exuvium can be used to separate cocoons of E. calleta (teeth present) and Rothschildia (teeth absent). Both genera are easily confused due to their similar pupal morphology. A final example is A. luna and A. polyphemus. Although these genera are often confused as larvae (Ferguson 1972:207), their mandibles are completely different, being either simple and toothed (A. luna) or complex with ridges (A. polyphemus). More descriptive studies of saturniid mandibles will no doubt yield further examples.

Acknowledgments

Reviews by G. L. Godfrey (Haskell Indian Nations University, Lawrence, Kansas), R. S. Peigler (University of the Incarnate Word, San Antonio, Texas), J. P. Tuttle (Tucson, Arizona), and R. D. Weast (Johnston, Iowa) significantly improved the manuscript. W D. Ol-hausen (Jesse Jones Park and Nature Center, Humble, Texas) provided keen observations concerning E. calleta in Harris County,

Texas. We are grateful to K. S. Johnson (Ohio University, Athens, Ohio) for Callosamia larvae and pupae, K. L. Wolfe (Escondido, California) for a R. erycina larval exuvium, C. A. Conlan (San Diego, California) for E. calleta pupal cases, M. D. Schmidt (Springboro, Ohio) for a H. euryalus pupa, and R. S. Peigler for use of his Oleaceae hostplant records.

At the The Ohio State University (Columbus, Ohio), we thank J. C. Mitchell for the scanning electron microscope photographs, D.J. Horn and G. D. Keeney for greenhouse space used to grow host-plants, and N. F. Johnson for use of the insect collection.

Voucher specimens of E. calleta and its hostplant are deposited in The Ohio State University's Insect Collection and Herbarium.

Literature Cited

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Bernays, E. A. & D. H. Janzen. 1988. Saturniid and sphingid caterpillars: two ways to eat leaves. Ecology 69:1153-1160.

Deml, R. & K. Dettner. 1993. Biogenic amines and phenolics characterize the defensive secretion of saturniid caterpillars (Lepidoptera: Saturniidae): a comparative study. J. Comp. Phys. B 163:123-132.

Dockter, D. E. 1993. Developmental changes and wear of larval mandibles in Heterocampa guttivitta and H. subrotata (Notodontidae). J. Lep. Soc. 47:32-48.

Ferguson, D. C. 1972. In Dominick, R. B. et al. (eds.), The moths of America north of Mexico. Bombycoidea. Saturniidae. Fascicle 20.2. 275 pp., 22 colored pis.

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Godfrey, G. L., J. S. Miller & D. J. Carter. 1989. Two mouth-part modifications in larval Notodontidae (Lepidoptera): their taxonomic distributions and putative functions. J. New York En-tomol. Soc. 97:455-470.

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LeMaire, C. 1978. Les Attacidae Americains. 1. Attacinae. Neuilly-sur-Seine, France. Published by the author. 238 pp.

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Received for publication 11 May 1997; revised and accepted 10 December 1999.