The Biology of Creatonotos (Lepidoptera: Arctiidae)
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<oologtcal Journal ifthe Linnean SocieQ (1989), 96: 339-356. With 10 figures The biology of Creatonotos (Lepidoptera: Arctiidae) with special reference to the androconial system Downloaded from https://academic.oup.com/zoolinnean/article/96/4/339/2658339 by guest on 01 October 2021 MICHAEL BOPPRE Forstzoologisches Institut der Universitat Freiburg, Fohrenbuhl 27, 0-7801 Stegen- Wittental, Federal Republic of Germany AND DIETRICH SCHNEIDER Max-Planck-Institut fur Verhaltensphysiologie, 0-8131 Seewiesen, Federal Republic of Germany Received January 1987, revised and accepted for publication October 1988 The reproductive biology of the arctiid moths Creatonotos transiens and C. gangis exhibits a novel ontogenetic phenomenon, the morphogenesis of male coremata size being directly controlled by the quantity of hostplant-derived pyrrolizidine alkaloids ingested by the larvae. In addition, the same alkaloids directly control the quantity of male pheromones synthesized and available for deployment by these scent organs. Reproduction in these insects thus shows striking linkages between ecological, behavioural, chemical and morphological features. This paper presents an account of the general biology of the moths, and reviews the literature on Creatonotos as a basis for reports on experimental work. KEY WORDS:-Creatonotos gangis - Creatonotos transiens - Arctiidae ~ Lepidoptera - androconial organs ~ sexual behaviour - chemical communication - pyrrolizidine alkaloids - reproductive biology. CONTENTS Introduction ................... 340 Material and methods ..... ............ 340 Notes on the life history .... ............ 341 General notes on the biology ... ............ 342 Morphology ofcoremata .... ............ 342 Variability of corematal size ... ............ 345 Corematal secretion ..... ............ 347 Behavioural use of coremata ............... 347 Discussion .................... 350 Morphological and chemical aspects ............ 350 Functional aspects ................ 351 Ecological aspects. .... ............ 353 Concluding remarks ..... ............ 354 Acknowledgements ..... ............ 354 References ................... 355 Note added in proof ..... ............ 356 339 00244082/89/080339 + 18 $03.00/0 0 1989 The Linnean Society of London 340 M. BOPPRB AND D. SCHNEIDER INTRODUCTION The arctiid genus Creatonolos Hiibner exhibits striking phenomena relevant to chemical ecology, sociobiology and developmental biology. The males possess inflatable androconial organs which vary in size in relation to the amount of pyrrolizidine alkaloids (PAS)ingested by the larvae from their hostplants. These hair-bearing scent organs emit a pheromone which is synthesized from PAS. While in the Lepidoptera male scent organs are usually expanded briefly during a final phase of courtship behaviour, males of Creatonotos display their coremata for long periods with or without the presence of females. Downloaded from https://academic.oup.com/zoolinnean/article/96/4/339/2658339 by guest on 01 October 2021 Here we present an account of what is known about the biology of Creatonotos, describe the morphology of the androconial system in some detail, discuss the scant and scattered literature on this genus, and provide some general ecological and behavioural information in order to supply a basis for earlier reports on experimental studies (e.g. Boppri. & Schneider, 1985; Wunderer et al., 1986) and further work in preparation. MATERIAL AND METHODS The genus Creatonotos presently comprises 15 or so species from Asia, Australia, and Africa. Our studies concern Creatonotos gangis (L.) and C. transiens (Walker) (Fig. 1 ) from Indonesia, where both species occur sympatrically. Adult moths were collected at a light near Dolok Merangir, North Sumatra, and laboratory cultures were established from field-caught females shipped to Germany. We kept the larvae, in groups of 1&50, in clear plastic containers of various sizes (depending on the size of the caterpillers) and, after having tested a variety of European (substitute) foodplants, we raised them routinely on leaves of Taraxacum ojicinale Web. and/or on a semi-artificial diet (see below). For morphological and behavioural observations we also used moths from larvae Figure 1. Males and artificially inflated coremata of C. gangis (left) and C. trunsiens (right). Note the different shape of the coremata which is typical for the species. Natural size. BIOLOGY OF CREATONOTOS MOTHS 341 which had ingested different amounts of pyrrolizidine alkaloids (PAS),either by feeding on PA-containing plants (see below), purified PAS extracted from plants and dispensed on Taraxacum leaves, or such PAS mixed into the diet. Adults were kept in plastic containers (520 x 280 x 250 mm) for mating; for observations on their behaviour larger cages (usually 980 x 650 x 570 mm) and red dark-room lights were used. Morphological studies of the coremata were made by dissection and by artificial inflation of the organs. For the latter, we introduced a plastic tube (3 mm in diameter) into the severed abdomen of a freshly killed male and gently applied air pressure through the tube by means of a syringe. Using this method, Downloaded from https://academic.oup.com/zoolinnean/article/96/4/339/2658339 by guest on 01 October 2021 coremata can be gradually inflated and deflated. For scanning electron microscopy (SEM), air-dried coremata were glued on aluminium stubs, coated with gold and observed with a Zeiss Novascan 30, operated at 15 kV acceleration voltage. To assess the different sizes of coremata, the organs were photographed and/or cut off and weighed on a micro-balance (Mettler H20T). NOTES ON THE LIFE HISTORY The larvae of both species are brown and very hairy (for descriptions see, for example, Piepers & Snellen, 1905; Kalshoven, 1981 : 323). They look very similar and the only obvious difference between them is their coloration (black with white pattern in C. transiens, dark brown with yellowish pattern in C. gangis). Under our breeding conditions (temperature 20-25°C; light-dark cycle 12 : 12 h), the development from egg to imago took 3945 days (egg: 6-7 days; seven larval stages: 3-4 days each; prepupa: 2-3 days; pupa: 8-10 days, females 1 day less than males). The young larvae appear to be gregarious and assemble in groups, at least for moulting. Nevertheless, cannibalism occasionally occurred, particularly in the last instar. Before starting to feed (about 24 h) after a moult, they consume their old skin. For pupation they spin a light cocoon, which is very hygroscopic and contains larval hair. Adult moths emerge in the middle of the photophase. There are few reports on larval foodplants of Creatonotos in the literature. For C. gangis, Fletcher ( 19 14) names coffee, groundnut, lucerne, and other low growing plants; further records are Brassica sp. (Brassicaceae) and Ipomoea reptans Poir (Convolvulaceae) (Anonymous, 1965), Imperata Cylindrica (Poaceae) (Robinson in Varley, 1962), sugar cane (Saccharum oficinarum, Poaceae), “Gramineae (Poaceae) and other plants’’ (Kalshoven, 1981), and <ea mays L. (Poaceae; K. Kanaujia, personal communication). The records for C. transiens are: Achras (Sapotaceae), Mangifera (Anacardiaceae), Lantana (Verbenaceae), Vitis (Vitaceae), Dioscorea (Dioscoreaceae) (van Eecke, 1930), Musa sp. (Musaceae), Paspalum conjugatum Berg (Poaceae), Pithecellobium dulze Benth. (Fabaceae) and Zea mays L. (Poaceae) (Anonymous, 1965), and Eleusine (Poaceae), vanilla ( Vanilla planzfolia, Orchidaceae) and Arachis (Fabaceae) (Kalshoven, 1981). Occasionally, Creatonotos has been reported as a pest (but never as a serious one) on sugar cane, vanilla and maize (e.g. van Deventer, 1912). Our cultures were usually maintained on dandelion, Taraxacum oficinale Web. (Asteraceae), sometimes on wheat, Triticum aestiuum L. (Poaceae). Both plants were readily accepted by the larvae which developed properly and resulted in 342 M. BOPPRE AND D. SCHNEIDER fertile adults of normal size. We also successfully used a bean-based semi- artificial diet (Bergomaz & Boppri., 1986). The larvae also accepted a great variety of other (European) plants, for example garden beans (Phaseolus sp., Fabaceae), Plantago sp. (Plantaginaceae), Sonchus sp. (Asteraceae) , Stellaria media Cyrillo (Caryophyllaceae) , Brassica pecinensis (Brassicaceae), spinach (S’znacia oleraceae, Chenopodiaceae) and various grasses. However, not all plants accepted by the larvae seem to be adequate or sufficient for normal development, if fed exclusively. Plants containing pyrrolizidine alkaloids (PAS) (e.g. Senecio sp., Eupatorium sp., Asteraceae; Crotalaria sp., Fabaceae; Heliotropium sp., Boraginaceae) were also Downloaded from https://academic.oup.com/zoolinnean/article/96/4/339/2658339 by guest on 01 October 2021 readily accepted. However, if the caterpillars were given a choice between PA- lacking and PA-containing plants, both were eaten and no obvious preference was observed (cf. Discussion). GENERAL NOTES ON THE BIOLOGY In the laboratory, the moths sit motionless when there is light and become active at dusk. First, they fly about for a while and eventually settle. Males then display their coremata (see below), while a little later females start emitting pheromones; this can be recognized by rhythmic movements of the abdomen. Mating is readily achieved in confinement; it occurs during the first 3-4 h of the night and takes 3-6 h. In coitu, the female wings always rest on those of the male, and multiple matings are not uncommon in captivity. Females start laying