Chromosome numbers are given for 1011 populations of 242 species, representing the full range of taxa (49 of the about 52 presently recognized genera) in the Neotropical Nymphalid butterfly subfamily Ithomiinae (prime movers for mimicry rings), including many additional geographical subspecies from 47 regions from México and the Caribbean islands throughout all tropical South American countries to southern Brazil. Twelve Neotropical Danainae (in 3 genera), all but one with n 0/29 Á/31, and the Australian Tellervo (n 0/32) served as sister groups for comparison. The numbers range nearcontinuously from n0/5 to n0/120 with modal values (33 Á/84 counts) at n0/12 Á/18, and only 16 and 26 counts at the usual modal number of all butterfly groups, n 0/30 Á/31. Superimposition of these changes in karyotype on a cladistic phylogeny of the subfamily indicates possible early halving of the complement to n about 14 Á/15, followed by much variation in each genus and tribe. While at least 17 species in 15 genera show stable karyotypes over much of the Neotropics, at least 40 species show large geographical variation in number of chromosomes, rarely accompanied by any evidence for reduction in fertility or incipient speciation. The evolutionary opportunism of the members of this subfamily probably accompanies their known population biology and community ecology: they are common, shade-loving, highly gregarious (occurring in small multispecies ''pockets'' in deep forest) and often migratory as a community when the environment becomes unfavorable (too hot or dry).

We describe the chromosome numbers of a monophyletic group of Satyroid subfamilies of primary fruit-attracted butterflies from South America: Charaxinae, Morphinae (including Brassolini) and Satyrinae. The charaxines do not have a distinct modal number. Their chromosome numbers are in the range n = 6-50, with n = 7-9, n = 12, n = 16, n = 19-21, n = 26, and n = 28-31 being the most common numbers. Within the Morphinae, the Morphini have a modal n = 28 and the Brassolini a modal n = 29, with few exceptions. The Neotropical satyrines, in particular the basal species, have a weak modal n = 29, which is a strong modal number in Palearctic satyrines. The African satyrines have an equally strong modal n = 28. Most Neotropical satyrines have, like charaxines, chromosome numbers lower than the weak modal n = 29, and often half this modal, but there are genera with stable numbers among the satyrines and charaxines. Evidently, the Neotropical satyroids descend from basal Nymphalidae with the typical lepidopteran modal number of n = 31, which have also given rise to the Heliconiini with modal n = 31 and 21 and Ithomiinae with modal numbers of n = 14-15.

We list the chromosome numbers for 65 species of Neotropical Hesperiidae and 104 species or subspecies of Pieridae. In Hesperiidae the tribe Pyrrhopygini have a modal n = 28, Eudaminae and Pyrgini a modal n = 31, while Hesperiinae have n = around 29. Among Pieridae, Coliadinae have a strong modal n = 31 and among Pierinae Anthocharidini are almost fixed for n = 15 while Pierini vary with n = 26 as the most common chromosome number. Dismorphiinae show wide variation. We discuss these results in the context of chromosome numbers of over 1400 Neotropical butterfly species and subspecies derived from about 3000 populations published here and in earlier papers of a series. The overall results show that many Neotropical groups are characterized by karyotype instability with several derived modal numbers or none at all, while almost all taxa of Lepidoptera studied from the other parts of the world have one of n = 29-31 as modal numbers. Possibly chromosome number changes become fixed in the course of speciation driven by biotic interactions. Population subdivision and structuring facilitate karyotype change. Factors that stabilize chromosome numbers include hybridization among species sharing the same number, migration, sexual selection and possibly the distribution of chromosomes within the nucleus.

We give the haploid chromosome numbers of 173 species or subspecies of Riodinidae as well as of 17 species or subspecies of neotropical Lycaenidae for comparison. The chromosome numbers of riodinids have thus far been very poorly known. We find that their range of variation extends from n = 9 to n = 110 but numbers above n = 31 are rare. While lepidopterans in general have stable chromosome numbers, or variation is limited at most a subfamily or genus, the entire family Riodinidae shows variation within genera, tribes and subfamilies with no single modal number. In particular, a stepwise pattern with chromosome numbers that are about even multiples is seen in several unrelated genera. We propose that this variation is attributable to the small population sizes, fragmented populations with little migration, and the behavior of these butterflies. Small and isolated riodinid populations would allow for inbreeding to take place. Newly arisen chromosomal variants could become fixed and contribute to reproductive isolation and speciation. In contrast to the riodinids, the neotropical Lycaenidae (Theclinae and Polyommatinae) conform to the modal n = 24 that characterizes the family.

We give the chromosome numbers of about 80 species or subspecies of Biblidinae as well as of numbers of neotropical Libytheinae (one species), Cyrestinae (4) Apaturinae (7), Nymphalinae (about 40), Limenitidinae (16) and Heliconiinae (11). Libytheana has about n032, the Biblidinae, Apaturinae and Nymphalinae have in general n 031, the Limenitidinae have n030, the few Argynnini n031 and the few species of Acraeni studied have also mostly n 031. The results agree with earlier data from the Afrotropical species of these taxa. We supplement these data with our earlier observations on Heliconiini, Danainae and the Neotropical Satyroid taxa. The lepidopteran modal n029 Á31 represents clearly the ancestral condition among the Nymphalidae, from which taxa with various chromosome numbers have differentiated. The overall results show that Neotropical taxa have a tendency to evolve karyotype instability, which is in stark contrast to the otherwise stable chromosome numbers that characterize both Lepidoptera and Trichoptera.