Journal of The Lepidopterists Society
The Lepidopterists' Society
About: Journal of The Lepidopterists Society is an academic journal. The journal publishes majorly in the area(s): Nymphalidae & Lycaenidae. Over the lifetime, 1082 publications have been published receiving 6554 citations.
Papers published on a yearly basis
TL;DR: The present paper reconstructs the history of understanding the migration of the monarch butterfly in North America and reflects the spirit in which Charles Remington, then a graduate student at Harvard, and his friend and colleague Harry Clench founded The Lepidopterists' Society are reflected.
Abstract: Since 1857, amateurs and professionals have woven a rich tapestry of biological information about the monarch butterfly's migration in North America. Huge fall migrations were first noted in the midwestern states, and then eastward to the Atlantic coast. Plowing of the prairies together with clearing of the eastern forests promoted the growth of the milkweed, Asclepias syriaca, and probably extended the center of breeding from the prairie states into the Great Lakes region. Discovery of overwintering sites along the California coast in 1881 and the failure to find consistent overwintering areas in the east confused everyone for nearly a century. Where did the millions of monarchs migrating southward east of the Rocky Mountains spend the winter before their spring remigration back in to the eastern United States and southern Canada? Through most of the 20th century, the Gulf coast was assumed to be the wintering area, but recent studies rule this out because adults lack sufficient freezing resistance to survive the recurrent severe frosts. Seizing the initiative after C. B. Williams' (1930) review of monarch migration, Fred and Norah Urquhart developed a program that gained the interest of legions of naturalists who tagged and released thousands of monarchs to trace their migration. Just as doubts in the early 1970s over whether there really were overwintering aggregations of the eastern population, on 2 January 1975 two Urquhart collaborators, Kenneth and Cathy Brugger, discovered millions of monarchs overwintering high in the volcanic mountains of central Mexico. This allowed a synthesis of the biology of this remarkable insect, including its migration and overwintering behaviors, its spread across the Pacific Ocean to Australia, its coevolution with milkweeds, and its elaborate milkweed-derived chemical defense which probably makes possible the dense aggregations during the fall migration and at the overwintering sites. Many important questions remain. Can monarchs migrate across the Gulf of Mexico? Can they migrate at night? Do they exploit strong tailwinds? Do they migrate to Central America? Do they overwinter elsewhere in Mexico or Central America? How much interchange is there between the eastern and western North American populations? How important is the fall migration along the Atlantic coast compared to the migration west of the Appalachian Mountains? What causes annual fluctuations in the size of the fall migrations? Beautiful and mysterious, the monarch's overwintering colonies in Mexico rank as one of the great biological wonders of the world. Unfortunately, these colonies are the monarch's Achilles' heel because of human population growth and deforestation in the tiny Oyamel fir forest enclaves. Additional risks arise from the increasing use of herbicides across North America which kill both larval and adult food resources. As a result, the migratory and overwintering biology of the eastern population of the monarch butterfly has become an endangered biological phenomenon. Without immediate implementation of effective conservation measures in Mexico, the eastern migration phenomenon may soon become biological history. In writing this paper for Charles Remington's honorarial issue of the Journal of the Lepidopterists' Society, fond memories flood forth of my days as his graduate student at Yale University from 1953 to 1957. My very first seminar lecture was on the migration of the monarch butterfly, Danaus plexippus (L.), and this set the stage for what will soon be 40 years of studying diverse aspects of the biology of this VOLUME 49, NUMBER 4 305 fascinating creature (reviews in Brower 1977a, 1984, 1985a, 1985b, 1986, 1987b, 1988, 1992). The present paper reconstructs the history of understanding the migration of the monarch butterfly in North America. To my knowledge, a detailed analysis of the ideas and the people who developed them has never been attempted. The story, a result of the combined observations of professional and amateur lepidopterists over more than a century, reflects the spirit in which Charles Remington, then a graduate student at Harvard, and his friend and colleague Harry Clench founded The Lepidopterists' Society in 1947 (Clench 1977). My purpose is to weave together the strands, to follow some of the red herrings, and to discuss several aspects of the migration biology that are still incompletely understood. Timely resolution of these questions should enhance efforts to preserve the monarch's mass migratory and overwintering behaviors which, regrettably, have become an endangered biological phenomenon (Brower & Pyle 1980, Brower & Malcolm 1989, 1991). The first great student of the monarch butterfly was Charles Valentine Riley, who emigrated from England and rose to lead midwestern, and then national entomology in the USA (Packard 1896, Essig 1931). In addition to being a first rate scientist, Riley was a talented artist who beautifully illustrated his descriptions of insect natural histories, and he fostered the English tradition of collating and publishing letters from a diversity of field observers, including many on the migration of the monarch. Anecdotal science on the monarch predominated well into the 20th century. In 1930, C. B. Williams of Edinburgh University reviewed monarch migration in his book, The Migration of Butterflies, which he periodically updated (Williams 1938, 1958, Williams et al. 1942). Shortly after the founding of The Lepidopterists' Society, Williams (1949:18) called for information from members and defined questions for much of the migration research that would follow: \"What happens to the butterflies that fly through Texas in the fall? Do they go on to Mexico? If so, do they hibernate there, or remain active, or breed?\" University of Toronto entomologist Fred A. Urquhart and his wife Norah took up the Williams challenge in 1940 and began tracing the fall migration of the monarch via a long-term tagging program, which would come to involve more than 3,000 research associates (Urquhart 1941,1952,1960,1978,1979,1987, Anon. 1955). The Urquharts communicated with their collaborators through an annual newsletter, published numerous papers on monarch biology, and carried on the tradition of incorporating amateurs' notes in their writings. According to Urquhart and Urquhart (1994), the final newsletter to their Insect Migration Association was issued as Volume 33 in 1994. Speculations about the destination of the eastern monarch migration 306 JOURNAL OF THE LEPIDOPTERISTS' SOCIETY became increasingly confused throughout the first three quarters of the 20th century because of the mysterious disappearance of what had to be vast numbers of butterflies that annually bred over an area of at least three million square kilometers. Many tortuous hypotheses were devised until resolution came in Urquhart's August 1976 National Geographic article announcing the discovery of the phenomenal overwintering aggregations in Mexico. This culmination of the Urquharts' lifetime efforts was one of the great events in the history of lepidopterology. FIRST OBSERVATIONS OF THE FALL MIGRATION: REPORTS FROM KANSAS TO CONNECTICUT Aside from a possible sighting of monarchs migrating in eastern Mexico during one of Christopher Columbus's expeditions (Doubleday & Westwood 1846-1852:91), D'Urban (1857) was apparently the first to report a migration of monarch butterflies. He described the butterflies appearing in the Mississippi Valley in \"such vast numbers as to darken the air by the clouds of them\" (p. 349). During September 1867 in southwestern Iowa, Allen (in Scudder & Allen 1869) described monarchs gathered in several groves of trees bordering the prairie \"in such vast numbers, on the lee sides of trees, and particularly on the lower branches, as almost to hide the foliage, and give to the trees their own peculiar color\" (p. 331). Although this clustering behavior was initially interpreted as a means of avoiding strong prairie winds, it soon became evident that it was associated with large southward movements of monarchs in the fall. The first collated evidence of massive fall migrations was published in 1868 by two American entomologists, Benjamin Dann Walsh and Charles Valentine Riley, who had independently emigrated from England to Illinois and were both keen to establish entomology as a science useful to farmers. Additionally, as evidenced in Darwin's correspondence (in F. Darwin and Seward 1903a:248-251, 1903b:385-386), Walsh and Riley were both influenced by The Origin of Species (Darwin 1859). Walsh, born in 1808, developed his interest in insects when he was nearly 50 years old, and launched his career in 1865 as associate editor of the Practical Entomologist in which he wrote, reprinted and edited numerous articles and letters, and answered letters from curious people and farmers besieged by insect pests. Within a decade he became the first Illinois State Entomologist (Riley 1870, Darwin and Seward 1903a). In contrast, Riley, born in 1843, had left his family home in England at the age of 17. By the time he was 20, he had begun publishing entomological notes in the Chicago-based Prairie Farmer (Ashmead 1895) and shortly thereafter became the journal's prolific entomological editor. In September 1868 the two men founded The American Entomologist, which Riley continued after Walsh died prematurely in VOLUME 49, NUMBER 4 307 1869 (Riley 1870). In 1868 Riley was appointed State Entomologist of Missouri, in 1876 he moved to Washington, D.C. to become Chief of the newly founded U.S. Entomological Commission, and shortly thereafter he founded the Smithsonian Institution's insect collections. Beginning in 1864, Riley used the Prairie Farmer to establish a correspondence network with midwestern farmers who were plagued by the migratory Rocky Mountain Locust. Combining his observations and high quality drawings with the information in hundreds of letters from farmers and lay
TL;DR: This paper summarizes the life histories of the known predatory and parasitic lepidopteran taxa, focusing in detail on current research in the butterfly family Lycaenidae, a group disproportionately rich in aphytophagous feeders and myrmecophilous habits.
Abstract: Moths and butterflies whose larvae do not feed on plants represent a decided minority slice of lepidopteran diversity, yet offer insights into the ecology and evolution of feeding habits. This paper summarizes the life histories of the known predatory and parasitic lepidopteran taxa, focusing in detail on current research in the butterfly family Lycaenidae, a group disproportionately rich in aphytophagous feeders and myrmecophilous habits. More than 99 percent of the 160,000 species of Lepidoptera eat plants (Strong et al. 1984, Common 1990). Plant feeding is generally associated with high rates of evolutionary diversification-while only 9 of the 30 extant orders of insects (Kristensen 1991) feed on plants, these orders contain more than half of the total number of insect species (Ehrlich & Raven 1964, Southwood 1973, Mitter et al. 1988, cf. Labandiera & Sepkoski 1993). Phytophagous species are characterized by specialized diets, with fewer than 10 percent having host ranges of more than three plant families (Bernays 1988, 1989), and butterflies being particularly host plant-specific (e.g., Remington & Pease 1955, Remington 1963, Ehrlich & Raven 1964). This kind of life history specialization and its effects on population structure may have contributed to the diversification of phytophages by promoting population subdivision and isolation (Futuyma & Moreno 1988, Thompson 1994). Many studies have identified selective forces giving rise to differences in niche breadth (Berenbaum 1981, Scriber 1983, Rausher 1983, Denno & McClure 1983, Strong et al. 1984, Futuyma & Moreno 1988, Thompson 1994). In particular, research on the Lepidoptera has emphasized how host choice may be governed on the one hand by the distribution of toxic secondary compounds and/or \"enemy free space,\" and on the other by the need to acquire adequate nutrients (e.g., Lawton & McNeill 1979, Atsatt 1981a, Strong et al. 1984, Bernays & Graham 1988, Stamp & Casey 1993). Since most species of moths and butterflies consume plants, comparatively little research has focused on the ecology and evolution of predatory taxa. Cottrell (1984) conducted a comprehensive analysis of aphytophagy in butterflies, but did not include moths. Reviews and experimental treatments of cannibalism in the Lepidoptera and other insects (e.g., Fox 1975, Polis 1981, Schweitzer 1979a, 1979b, Elgar & Crespi 1992) contain useful discussions of the biology of carnivorous species. However, it has been more than fifty years since a full survey VOLUME 49, NUMBER 4 413 of the life histories of predatory Lepidoptera has been published (Balduf 1931, 1938, 1939, Brues 1936, Clausen 1940). The great emphasis on phytophagous species overlooks the considerable dietary diversity exhibited by Lepidoptera as a whole, and yet a consideration of both the scope of this diversity and its limitations can provide valuable insight into the ecology and evolution of the group. The rarity of carnivorous Lepidoptera is particularly striking considering the enormous dietary range exhibited by other holometabolous orders containing phytophages, such as Coleoptera, Hymenoptera and Diptera. Only about 200 species representing eight superfamilies are known to be obligate predators or parasites. Moreover, as predators, lepidopterans are remarkably unadventuresome, feeding mostly on slow, soft-bodied scale insects, eggs of other insects or ant brood. The few parasitic species are primarily parasites of other insects. In this review, I summarize what is currently known about the life histories of moths and butterflies with carnivorous larvae, and discuss outstanding features of their ecology and evolution. The review begins with a description of traits that appear to be associated with obligately carnivorous life styles, and then focuses on recent research into predatory species in the butterfly family Lycaenidae. It concludes with discussion intended to stimulate further inquiry into the evolution of carnivory in the group. Balduf (1938) recognized four main types of entomophagous caterpillars: (1) cannibals, which largely represent diversions from otherwise phytophagous lifestyles; (2) occasional predators, which include species that sometimes attack non-conspecific caterpillars and scavengers that sometimes take prey living in the same habitat; (3) habitual predators, such as species that regularly feed on homopterans or insects such as ants; and (4) parasites/parasitoids, including the few species that undergo either part of, or their entire development feeding on a single host. This review primarily concerns species in categories 3 and 4, which together comprise the group of obligate carnivores, while the members of 1 and 2 are facultatively entomophagous. As a rule of thumb, I consider parasites/parasitoids to be those that consume their hosts in units of less than one, whereas true predators kill and consume more than one prey. I have not distinguished here between parasites and parasitoids (that ultimately kill their hosts), in part because relatively little is known about whether or not parasitic Lepidoptera eventually do kill their hosts. The term parasite is used hereafter in this collective sense. The life histories of entomophagous Lepidoptera are summarized in three tables. Table 1 covers the life histories of carnivorous moths. Table 2 summarizes carnivorous groups within the butterfly family Lycaen414 JOURNAL OF THE LEPIDOPTERISTS' SOCIETY idae other than Miletinae . Table 3 focuses on feeding specializations within the wholly carnivorous lycaenid subfamily Miletinae. I have attempted to include every record of obligate predatory or parasitic behavior I could find. Because of the lack of complete life history information for many groups, this summary is inevitably tentative, and will evolve as new information becomes available. I have not attempted to summarize the numerous records of scavenging, lichen feeding or cannibalism in the group, although I discuss their possible significance. Because a caterpillar is usually observed consuming only one prey item at the time of collection, inference and/or interpretation is sometimes necessary in designating species as predators or parasites. I have indicated in the Tables those instances where parasitism or predation have been strongly inferred for a particular species or group, rather than confirmed by direct observation. The arrangement of taxa within the Tables follows the classification for the Lepidoptera put forward by Nielsen & Common (1991) and ScobIe (1992). The broad outlines of this classification were provided by Kristensen & Nielsen (1983), Kristensen (1984a, 1984b), and Nielsen (1989), and more detailed information on the Australian taxa have been supplied by Common (1992). I refer here to \"Homoptera\" for clarity with respect to older literature, although \"Hemiptera\" is the appropriate designation for this group (their arrangement in Table 1 follows Carver et al. 1991). In the case of the Lycaenidae, controversy remains concerning the relationships among the main lineages, as well as relationships within each of the groups. I follow the classification proposed by Eliot (1973), which was modified by Fiedler (1991), and which Eliot revised in 1992 (Eliot in Corbet et al. 1992), as well as Eliot's revision of the Miletini (1988). In his 1992 revision, Eliot included the riodinines as a subfamily of the Lycaenidae (Ehrlich 1958, Kristensen 1976, d. Harvey 1987, Robbins 1988, Scott & Wright 1990), and I will refer to them here as a subfamily, recognizing that their appropriate taxonomic rank remains uncertain. I. OVERVIEW OF PREDATORY LEPIDOPTERA Convergently derived origins. Fossil remains suggest that the larvae of the earliest Lepidoptera fed on mosses, while the adults possessed mandibulate mouthparts and fed on pollen (Kukalova-Peck 1991). The most \"primitive\" extant Lepidoptera are in the suborder Zeugloptera, containing the homoneurous family, the Micropterigidae, which are considered to be the sister group to all other Lepidoptera (Common 1990, Nielsen & Common 1991). Zeuglopteran larvae have been described (Kristenson 1991:140) as '''soil animals' occurring in moist situations (bryophyte growths, etc.) which would seem to be only a small VOLUME 49, NUMBER 4 415 step away from genuine aquatic habitats\" which characterize the larval habitats of their close relatives, the Trichoptera (see also Powell 1980, Tuskes & Smith 1984). In New Zealand, members of the genus Sabatinca feed on liverworts. In Australia, larvae have been collected from rotten logs in Queensland. Other species are known to feed on herbaceous plants, including grasses (Nielsen & Common 1991). From these accounts, we can conclude that the Micropterigidae are primarily plant or detritus feeders. Carnivory is therefore likely to represent a derived condition in the Lepidoptera, although without appropriate phylogenies in each case, the polarity of shifts in feeding specialization must remain speculative. Nevertheless, the occurrence of predatory habits in eight separate lepidopteran superfamilies (Table 1) suggests that the trait has arisen convergently several times. A closer examination of the phylogenetic distribution of carnivory reveals further evidence of convergent origins. Within the butterflies, the family Lycaenidae (sensu Ehrlich 1958, Eliot in Corbet et al. 1992) contains about 5,455 described species, or close to 32% of all butterflies (Shields 1989). At least 80 species are known to be carnivorous or to feed on substances other than plants (Tables 2 & 3), and an additional circa 70 species are suspected to be aphytophagous. Cottrell (1984) argued that aphytophagy evolved independently at least eight times in the Lycaenidae (not including the riodinines), and DeVries et al. (1992) have recently added two instances of aphytophagy in the Riodininae that may well represent an independent origin. Phylogenetic distribution of predatory and parasitic species. Obli
TL;DR: It is shown, by scrutinizing sequence length and composition, that DNA barcodes separate the species after all, and the various degrees to which larval diets, although specialized, are unreliable for species discrimination.
Abstract: Unlike most species of Lepidoptera whose DNA barcodes have been examined, closely related taxa in each of three pairs of hesperiids (Polyctor cleta and P. polyctor, Cobalus virbius and C. fidicula, Neoxeniades luda and N. pluviasilva Burns, new species) seem indistinguishable by their barcodes; but that is when some of the cytochrome c oxidase I (COI) sequences are short and sample sizes are small. These skipper butterflies are unquestionably distinct species, as evidenced by genitalic and facies differences and by ecologic segregation, i.e., one species of each pair in dry forest, the other in adjacent rain forest in Area de Conservación Guanacaste in northwestern Costa Rica. This national park is the source of the specimens used in this study, all of which were reared. Larval foodplants are of no or problematic value in distinguishing these species. Large samples of individuals whose barcodes are acceptably long reveal slight interspecific differentiation (involving just one to three nucleotides) in all three pairs of skippers. Clearly, the chronic practice of various taxonomists of setting arbitrary levels of differentiation for delimiting species is unrealistic. Additional key words: Area de Conservación Guanacaste, Costa Rica, dry forest, rain forest, foodplants, genitalia, Neoxeniades pluviasilva Burns, n. sp. A DNA barcode is the base pair (bp) sequence of a short (~650 bp), standard segment of the genome (Hebert et al. 2003). In animals, this is part of the mitochondrial gene cytochrome c oxidase I (COI). Because the COI gene generally mutates at evolutionarily rapid rates, comparison of barcodes in a sample of individuals best reveals differentiation at low taxonomic levels. Hence barcodes can be extremely useful in distinguishing and identifying species. Coupling this concept with the idea of always comparing the same short length of COI across a wide diversity of taxonomic groups—and doing so with demonstrable success—is what led to the catchy name “DNA barcodes” (Hebert et al. 2003). Even though COI had been used effectively in various evolutionary and taxonomic studies at and around the species level well before this epithet appeared, in the few years since its introduction, barcodes have been used for their specific purpose with notable results and with rapidly increasing frequency. The rearing of myriad wild-caught caterpillars in Area de Conservación Guanacaste (ACG) in northwestern Costa Rica is now approaching its thirtieth year (for information about both site and rearing process, see Miller et al. 2006, Janzen & Hallwachs 2006, Burns & Janzen 2001). DNA barcodes (of a total of 4,260 reared adults) have been able to distinguish among almost 98% of 521 previously known species of the lepidopteran families Hesperiidae (skipper butterflies), Sphingidae (sphinx moths), and Saturniidae (wild silk moths) VOLUME 61, NUMBER 3 139 (Hajibabaei et al. 2006, Janzen et al. 2005). Rare cases where barcodes failed, which always involved closely related congeners, are worth examining in more detail. In this paper we treat three such pairs of congeneric skipper species (noted in Hajibabaei et al. 2006:table 1). We map the ecologic separation of the species in each pair in and very near ACG. We document the species status of each member of a pair (and describe one as new) on morphologic grounds. We discuss the various degrees to which larval diets, although specialized, are unreliable for species discrimination. And we show, by scrutinizing sequence length and composition, that DNA barcodes separate the species after all. Despite the immense value of DNA barcodes and the fact that they have often indicated overlooked species, it is important to consider characters besides the barcodes themselves—a point made repeatedly in the revelation of 10 cryptic species hiding under the one name Astraptes fulgerator (Walch) in ACG (Hebert et al. 2004). THE SPECIES PAIRS IN QUESTION Ecologic separation (Figs. 1-3). Each pair comprises a dry-forest species and a rainforest species. Parapatry of this kind is a recurrent distribution pattern among closely related lepidopteran species in ACG. In each pair of the following list, the dry-forest species comes first: Polyctor cleta Evans and P. polyctor (Prittwitz), Cobalus virbius (Cramer) and C. fidicula (Hewitson), Neoxeniades luda (Hewitson) and N. pluviasilva Burns (a new species described below). Polyctor is a pyrgine genus, and Cobalus and Neoxeniades are hesperiine genera. From our distribution data, parapatry in both pairs of hesperiine species appears to be complete (Figs. 2, 3) whereas that in the pyrgine pair does not (Fig. 1). Out of 211 reared individuals (wild-caught as caterpillars) of the rainforest species P. polyctor, four came from dry forest. The genitalia of these apparent strays have been KOH-dissected and thoroughly studied to be sure of FIG. 1. Spatial distribution of Polyctor cleta and P. polyctor in and near ACG. 140140 JOURNAL OF THE LEPIDOPTERISTS’ SOCIETY their specific determination. Because both species of this essentially parapatric pair of Polyctor eat the same three species of foodplants (Table 3), and because one of these plants occurs in both rain and dry forest, a female wandering from rain forest can find an attractive foodplant in dry forest and oviposit on it. The flight of these skippers is far stronger than necessary to travel the distance involved. Of the four P. polyctor caterpillars found in dry forest, three were eating the species of foodplant most often eaten by this skipper in rain forest (and because two of those were found on the very same plant, they are probably offspring of a single female); the fourth caterpillar was eating an exceedingly common, but strictly dry-forest, species that is by far the preferred foodplant of P. cleta. A small number of P. cleta caterpillars found in disturbed ecotone between dry and rain forest, and less than 2 km from the latter, were eating the main foodplant of P. polyctor. KOH-dissection and examination of the genitalia of the four adults reared from this group gave no hint of hybridization. Morphologic differences (Figs. 4-41; Tables 1, 2). In all three pairs, the brown ground color of the adult averages paler in the dry-forest species than it does in its rainforest counterpart (Figs. 4–27). This is especially evident when comparing long series of more or less recently reared (therefore unfaded) specimens. In both sexes of Polyctor, a spot spanning the distal end of the forewing cell is hyaline in P. cleta but opaque in P. polyctor. A male secondary sex character in these species of Polyctor comprises a tuft of long hairlike scales arising near the base of the dorsal hindwing costa, as well as an elongate patch of pale specialized scales embraced by the swollen beginning of vein 7 and a similarly swollen, closely adjacent length of vein 6; in both veins, swelling extends out to the end of the cell; and the hairlike scales are long enough to overlie the special patch. These presumably pheromone-disseminating hairs are mostly to entirely dark in P. cleta but pale (often orangish) in P. polyctor (cf. Figs. 4 and 6). FIG. 2. Spatial distribution of Cobalus virbius and C. fidicula in and near ACG. VOLUME 61, NUMBER 3 141 Though clearly variations on a theme, the male genitalia of these two Polyctor species differ in striking ways. Despite substantial individual variation, almost every genitalic part differs interspecifically to at least some extent; but it is the highly asymmetric valvae that differ most (see Table 1 and cf. Figs. 28–33). Even the less elaborate female genitalia are notably distinct in the two species (Table 2). Both species of Cobalus, which are predominantly brown, have a conspicuous white patch both dorsally and ventrally on a distal area of the hindwing. In ACG specimens, this patch is restricted to males of C. fidicula but expressed by both sexes of C. virbius (Figs. 8–11, 20–23), except for two females in which it is barely perceptible. Both species express it more fully ventrally than dorsally. In C. fidicula the patch stops before the outer margin so as to leave a narrow strip of dark brown ground color, ventrally the patch extends from mid space 1c to vein 6, and the white of the patch looks creamy on the ventral surface. In C. virbius the patch reaches the outer margin, ventrally extends from the tornus to vein 6, and looks pure white on both wing surfaces. Lateral orange scaling—broad on the outer side of the palpus and narrow behind the eye—is bright in C. fidicula but just dully suggested, and only on the palpus, in C. virbius. Cobalus fidicula is a little larger than C. virbius, and its forewing hyaline spots are likewise larger. The male genitalia (which are symmetric) differ in two obvious respects. The ventral distal division of the valva is longer and dorsally dentate in C. fidicula (cf. Figs. 35 and 37). The very broad uncus in dorsal view shows a pair of prominent lateral swellings in C. virbius (cf. Figs. 34 and 36). Neoxeniades pluviasilva Burns, new species (Figs. 3, 14, 15, 26, 27, 40, 41, 45, 46; Table 3) Etymology. The species name, a noun in apposition, comes from the Latin pluvia for rain and silva for forest. Diagnosis. This is a rainforest species whereas FIG. 3. Spatial distribution of Neoxeniades luda and N. pluviasilva in and near ACG. 142142 JOURNAL OF THE LEPIDOPTERISTS’ SOCIETY N. luda is a species of the dry forest (Fig. 3). At a glance, N. pluviasilva is darker than N. luda and does not express a large, pale, outer marginal area on the ventral side of the hindwing nearly as well (cf. Figs. 26, 27 with 24, 25). In females of N. pluviasilva, the double hyaline cell spot of the forewing extensively overlaps the spot in space 2 whereas in N. luda females, this forewing cell spot overlaps the spot in space 2 little or not at all (cf. Figs. 15, 27 with 13, 25). Description. Member, with N. luda, of mainly South American N. scipio species complex—t
TL;DR: For example, Calvert et al. as mentioned in this paper studied the migration behavior of monarch butterflies in the Transvolcanic Belt of central Mexico and found that during November and December the numerous small groups consolidate into a few large compact aggregations and move downward into more protected positions closer to water.
Abstract: Each year monarch butterflies migrate from breeding grounds in the United States and Canada to the Transvolcanic Belt of central Mexico. Here, within the montane fir forests, they initially aggregate in small groups of loose clusters scattered along high ridge crests. During November and December the numerous small groups consolidate into a few large compact aggregations and move downward into more protected positions closer to water. Butterfly activity increases in the last half of February due to seasonal warming. The consolidation and compaction processes that marked the beginning of the season reverse, and the colonies spread out and often split into two or more parts. After mid-March, colony size decreases as the butterflies begin to remigrate northward. Several characteristics of the climate and physiography of the Transvolcanic Belt, including moisture, altitude, and slope exposure and inclination, are important to the overwintering biology of the monarch butterfly. The forests of the zone playa major role in satisfying the overwintering monarchs' microclimatic requirements by moderating temperature extremes and conserving moisture. By colonizing this high altitude area in the tropics, the butterflies appear to satisfy microclimatic requirements that include temperatures low enough to keep activity, metabolism, and lipid expenditure to a minimum, but not so cold as to cause freezing; sufficient solar input to allow thermoregulatory basking and consequent flight; and sources of moisture and nectar. Each autumn, millions of monarch butterflies (Danaus plexippus L.) migrate southwest or south (Urquhart & Urquhart 1978, Schmidt-Koenig 1979) from breeding grounds in eastern and central United States and southern Canada to overwintering sites in Mexico. Funneling through Texas, they cross into Mexico and encounter the southern extension of the Rocky Mountains, the Sierra Madre Oriental. Here they change their southwesterly course and follow the ranges to the southeast, eventually cross them, and continue to the Transvolcanic Belt, the volcanic mountains that extend across the southern end of Mexico's Central Plateau (Altiplanicie Mexicana) between 19° and 200N latitude. At a few isolated places within the high altitude coniferous forests, which are scattered through this belt of mountains (Fig. 1), monarchs spend the winter in aggregations estimated to be in the tens of millions (Brower et al. 1977, Calvert, in prep.). Monarchs migrate south in the fall to avoid winter cold and survive in cool, moist places where they can conserve fuel reserves in a state of reproductive inactivity until making the return trip north in the spring. Yet weather in the overwintering areas does not ideally meet monarch requirements. Not only do temperatures occasionally fall into the lethal range (Calvert et al. 1983), but also intense insolation on VOLUME 40, NUMBER 3 165 clear and partly cloudy days stimulates butterfly activity to an extent that appears to contradict their need to conserve fuel. In an attempt to resolve these apparent contradictions, and to understand better why the monarchs choose these particular areas in Mexico, we here describe characteristics of the annual overwintering cycle and ecological features of several overwintering areas that we studied for nine seasons (December 1976 through spring 1985). PHYSIOGRAPHIC FEATURES, CLIMATE AND VEGETATION Volcanic cones and ranges dominate the terrain of the Transvolcanic Belt, which has an area of 60,000 km2, and measures approximately 640 km across by 95 km wide (Moore 1945). To the north it is bounded by the high Mexican plateau, and on the south by the large Balsas River drainage (Rzedowski 1978). Its eastern portion averages 2200 m elevation with numerous peaks rising above 3600 m, including the highest mountains in North America south of Alaska (Goldman 1951). The western portion contains fewer high peaks, and declines in elevation towards the Pacific. The central area where the monarch colonies are located (Fig. 1) is drained to the north and east by the Rio Lerma and to the south and west by the Balsas-Mezcala river system (Arbingast et al. 1975). Classic wet-dry season weather patterns prevail through most of the Transvolcanic Belt. Precipitation and heavy clouding is frequent from May until October, especially in the mountains, but winters are dry, and arid conditions prevail on the interior plains (Goldman & Moore 1945). However, winter and early spring storms occasionally occur in the area, and the higher elevations are subjected to high winds, heavy rains, snow, and ice storms (Mosina-Aleman & Garcia 1974). While potentially lethal to the overwintering butterflies (Calvert et al. 1983), these storms are also beneficial because they reduce the severity of the winter drought in the high-elevation overwintering areas. Because of the wide range of altitudes and climatic conditions, vegetation within the Transvolcanic biotic province is extremely varied. High interior plains and valleys consist largely of grasslands intermixed with patches of small trees, shrubs, yuccas, agaves and cacti. On mountainous slopes, forests dominated by oaks and pines give way to firs at about 2750 m (Goldman 1951), but in more humid areas, the firs commence as low as 2400 m (Rzedowski 1978). On the highest peaks, firs give way to alders and other species of pine and eventually to grassland and tundra (Goldman 1951, Goldman & Moore 1945). As is true of the lower limits, vegetational transitions depend on moisture and exposure, and the altitudinal limits of the fir zone may be influ-