[Butterfly Header - North American Butterfly Association]

Top: Chlosyne ehrenbergi is a Mexican endemic, found only in west-central Mexico, Mar. 21, 1993, San Jose Vista Hermosa, Oaxaca

Middle: Meton Hairstreak is a widespread tropical species. Males, because of their unique pale violet iridescence above, may be the only hairstreaks identifiable from a fast-moving car! Jan. 19, 1997, Catemaco, Veracruz

Below: Greta morgane is one of the many clearwings that fly in the shade of Mexican forests, Jan. 4, 1992. Above Atoyac, Guerrero

Mexican Butterfly Diversity

by Manuel A. Balcázar-Lara

For centuries, Mexico has attracted the attention of naturalists and zoologists from all over the world. As a child, I soon discovered two of the main reasons for this interest: a very high number of species present in our country, and the presence of endemics, species and subspecies found only within Mexico, many of which exhibit "primitive" characters. I dreamed of searching for butterflies in the forests of Chiapas (the southernmost Mexican state) when I learned that there were as many types of butterflies found there as in the entire United States and Canada. On the other hand, I recall identifying my first Baronia Swallowtail (Baronia brevicornis), found only in Mexico, and reading that this was a "paleoendemic" butterfly (What an impressive adjective!) exhibiting some of the most primitive features of any living butterfly. Later, I learned that, among other reasons, Mexico's high biodiversity (approximately 10% of the world's terrestrial fauna) was the result of its geographic position (located between the New World temperate and tropical regions), and its great diversity of climate, topography, and ecological systems. All of this made a deep impression that led me to the professional study of butterflies.

   I have always been attracted to "insect numbers." Recently, the number of species of insects of the world has been the focus of a vigorous debate. Several figures have been given, from the traditional number of less than a million to the 30 million proposed by Terry Erwin in 1982. A more conservative estimate of the number of insects is that of Stork, who calculated a number between three and four million. Using Stork's number, our estimate of the number of insect species present in Mexico is between 300,000 and 400,000 (or between three and four million if we use Erwin's number).

   Heppner estimated the total number of Lepidoptera worldwide to be 250,000. If the estimate that 10% of the world's fauna is found in Mexico holds for Lepidoptera, this would indicate that around 25,000 species of Lepidoptera will be found in Mexico. The worldwide number of butterflies (not including the skippers) described is about 20,000, and in Mexico, 1200 have been found to date. Thus Mexico's butterfly fauna represents about 7% of the total known for the world. It comes as no surprise then that Mexico has been treated as a "megadiversity" country, with some authors ranking Mexico as the third most diverse country in the world.

A spot-celled Sister is just one of the many sisters found throughout Mexico, Feb. 13, 1995, Mismaloya, Jalisco

   The interest in, and study of, Mexican butterflies predates the arrival of the first Europeans. Although most of the knowledge that prehispanic cultures had about butterflies has been lost, we can still appreciate the importance that butterflies had for these cultures by viewing their fresco paintings and pottery. Perhaps some of the outstanding and best known examples are the representations of the goddess "Xochiquetzal" in the form of a Two-tailed Swallowtail.

   The starting point for the modern study of Mexican butterflies was the publication of the Biología Centrali-Americana by Godman and Salvin from 1887-1901. In this work, several new species were described and illustrated. The excellent plates and careful descriptions made this book the basis for future research. Another very significant event was the publication of the Macrolepidoptera of the World by Seitz from 1906-1924. These two works were the major references for the study of Mexican butterflies for a very long time and are still used today. The first catalog of Mexican butterflies was created by C.C. Hoffmann in 1940. Since then, several others have added to our knowledge of Mexican butterflies. Researchers at the National Collection of Insects (Instituto de Biologia) and the Zoology Museum (both at the National Autonomous University of Mexico), as well as many amateurs, have been studying the butterflies of Mexico. Foreigners, especially Americans, have also made a great contribution to our knowledge.

Huge White Morpho (above, June 7, 1994, Ahuacapan, Jalisco) (photo by Andrew D. Warren)

   Although the butterfly diversity has been explored by many field biologists over the last decades, our knowledge of vast areas is still very rudimentary. This is particularly so for the northern states and the plateau. Not surprisingly, the states with better butterfly checklists are also those that have the highest numbers of publications:Veracruz, Chiapas, Guerrero, San Luis Potosí, and more recently, Baja Calfornia, Jalisco, Oaxaca, and Colima. There are historical reasons for these states to be better known when compared to other states. Veracruz and Guerrero were respectively the Atlantic and Pacific entrance gates to Mexico since colonial times, so collecting sites were along the paths from the ports to Mexico City. Because the areas covered with tropical rain forests maintain very rich butterfly faunas, some of these forests have also been quite well-studied. Other areas that are well-studied include sites with rare or very beautiful species that have attracted collectors. It is easy to understand that butterfly enthusiasts look for areas such as the Sierra de Juárez where one can observe in a small area gorgeous butterflies such as Esperanza Swallowtail, several species of preponas, eighty-eights, agrias, morphos, and more! So far, data from published papers show that the richest localities studied are: Chajul in Chiapas (396 spp.) Los Tuxtlas area in Veracruz (452 spp.) and the Sierra de Juarez in Oaxaca (450 spp.). Each of these areas has almost 40% of the total number reported from Mexico. The richest geographic areas are located in regions to the south and southeast; areas of enormous climatic, vegetational, and physiographic heterogeneity. Also, these areas have a high environmental complexity that includes patches of well preserved and slightly altered habitats.

Mid-sized, red-eyed spreadwng skipper  Ocyba calathana (Feb. 8, 1995, Mismaloya, Jalisco)

   On the other hand, the centers of distribution for endemic butterflies is radically different from the species-rich areas in Mexico. The great majority of the endemic butterflies of Mexico are found in the North and in the dry areas in the South and West. Another important group of endemics are restricted to the cloud forest, in "islands" or isolated humid submontane patches on the sierras. Mexican endemic species have patchy distributions because of the heterogeneous distribution of the dry, humid and montane environments, a reflection of the complex geological history of Mexico. There are several areas of endemism in Mexico. Among the dry areas are the Balsas Basin, the Pacific slope from Nayarit to the Isthumus of Tehuantepec, and the dry Chiapas Central Depression stand out. On the other hand, the most outstanding areas for cloud forest endemics are in Nayarit (Nueva Galicia), Sierra Madredel Sur (Guerrero-Oaxaca), Soconusco in Chiapas, Sierra de Juárez in Oaxaca and the Atlantic slope of Chiapas. These areas are not often visited by butterfly enthusiasts since deserts are not usually thought to hold many, or rare, butterflies. On the other hand, cloud forests are often quite discouraging because the sun can be blocked by clouds for weeks at
a time, and butterflies may be almost absent without direct sunlight. But in both cases, I remember trips when, at the right time, most of the butterflies we found were either endemic or considered rare.

Diminutive White Scrub-Hairstreak (Jan. 7, 1992, Ixtapa, Guerrero)

   Unfortunately, some of the areas that hold endemic buterflies are among the least known. Only eight of the 31 Mexican states have reliable butterfly checklists. Thus, making decisions as to where and when to spend conservation resources is extremely difficult. In addition, in Mexico, very little has been done to study life cycles, in comparison to the number of such studies performed in countries such as Costa Rica and El Salvador. All the remaining work to be done cannot be achieved by the few active specialists working in the area. Thus, there is an important opportunity for butterfliers to contribute a great deal to the knowledge of Mexican butterflies. Cooperative efforts must be undertaken in order to gather this most-needed information

All photographs this article by Jeffrey Glassberg, except as indicated.

11 Oct 1998 / Main Page