Introduction

A curious relationship exists between a group of plants, the pyrrolizidine alkaloids they contain, and tiger moths of the family Arctiidae. Tiger moths possess an impressive array of chemicals, either produced de novo or sequestered from plants, that protect them to a greater or lesser degree from predators and parasites. These chemicals include cyossin (Teas et al., 1966), biogenic amines (Bisset et al., 1959, 1960; Rothschild and Aplin, 1971), pyrazines (Rothschild et al., 1984), polyphenolics (Hesbacher et al., 1995), iridoid glycosides (Bowers and Stamp, 1997), and cardenolides (Rothschild et al., 1970, 1973; Wink and von Nickisch-Rosenegk, 1997); however, no group of compounds, it seems, has influenced the natural history and behavior of tiger moths as the pyrrolizidine alkaloids (PAs) have done (Weller et al., 2000a). Several excellent reviews have been written about these compounds from the perspective of their chemistry, the plants that produce them (Bull et al.; 1968; Mattocks, 1986; Hartmann and Witte, 1995), and the insects that utilize them (Schneider, 1986; Boppré, 1990; Hartmann and Ober, 2000), but none has focussed exclusively, on their intimate relationships with tiger moths.

The members of the family Arctiidae, which numbers over 11 000 species, are often brilliantly colored (Watson and Goodger, 1986; Holloway, 1988; Weller et al., 2000a). In addition to standard aposematic red, yellow, or black patterns, adults and larvae may have iridescent blue and green, or even pearly white, coloration. White can be considered aposematic when individuals rest conspicuously on green vegetation.