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Lepidoptera chromosome numbers range from n = 7 to n = 220; however, n = 29–31 is most common. There are far more species with <29 chromosomes than there are with >31, suggesting that chromosomal fusions have been more frequent and evolutionarily successful than fissions through time (WHITE 1973). However, even within Heliconius there is variation in chromosome number; for example, H. sapho has a large number of small chromosomes (n = 56–57; BROWN et al. 1992). Thus, the anchor loci identified here would likely be of limited use in identifying conserved chromosomal linkage groups in H. sapho, and it remains an open question as to why certain species have undergone very rapid chromosomal evolution against a background of considerable stability.