Diversity and Abundance: Butterflies of Mexico

By Moralea Milne

Nothing ignites my passion more than butterflies and moths, those winged miracles of beauty and complexity that are found throughout the world. Mexico is especially blessed with a diversity and abundance, home to approximately 1750 species of butterflies alone.
One of the greatest and most miraculous migrations on earth is the story of the Monarchs and their journey from their Mexican winter home to their third generation arrival and procreation in Canada. These Canadian born and breed monarchs emerge from their cocoons in late summer or early fall and begin their 4800 km trip to their forest hibernation site in Michoacan, where they overwinter before their flight into the southern states, to mate and die. The next generation will fly to the mid-states, laying their eggs and creating the generation who will complete the trip to Canada.
How does that Canadian cohort know to migrate south, to follow routes that will take them to the same small forested area of one region of Mexico, even to particular trees? It is one of life’s mysteries that has captured the imagination of countless individuals and scientists. The monarchs have seen a number of challenges to their survival in the past, especially from logging in and around their hibernation site.
However this past year (2013) has seen a dramatic 43% decrease in the number of monarchs arriving in Mexico. Biologist Karen Oberhauser of the University of Minnesota has pinpointed the increased use of Monsanto’s Roundup herbicides in the United States and Canada as a culprit. The Monarchs use only milkweed as the host plant on which to lay their eggs and feed their caterpillars. The increased use of Roundup in particular has had a devastating impact on milkweed populations, without milkweed, there can be no Monarchs. Besides the popular Monarchs, there are few other common butterflies that you could soon come to know and appreciate.

Mexican Fritillary
(Euptoieta hegesia)
Fritillaries are in the large family known as brush-footed butterflies or Nymphalidae. Generally these are medium to large butterflies (Mexican fritillaries are 6.5-7.5 cm), most with a pair of small or reduced forelegs (appearing like they have only four legs instead of six). A great number of Nymphalidae are brightly coloured and often hold their wings flat when resting, providing an excellent photographic opportunity. Frequently the underwings are dull or cryptically coloured and patterned. Caterpillars are hairy or spiky and in the case of the Mexican Fritillary, they have two projections from just behind their head, looking much like antennae. Caterpillars are red (usually a sign to predators that they are toxic), with black spines and white longitudinal lines edged in black.
Mexican Fritillaries are found throughout Mexico at any time of the year, flying swiftly and erratically over low vegetation, nectaring on lantana and verbena as well as sipping at the occasional dung pile. Passionflower and morning glory families are host plants on which the single eggs are laid, and upon which the caterpillars feed. It is thought that ingesting the cyanogenic glycosides (cyanide compounds) that are contained in the passionflower plants protect the larva from some terrestrial predators, such as the Anolis lizards. There are number of fritillary species that you can find around Puerto Vallarta, this one has the fewest markings on the top side of the hind wings.

Ceraunus Blue
(Hemiargus ceraunus)
Ceraunus Blues are members of the gossamer-winged butterfly family (Lycaenidae), which include the Blues, Coppers, Hairstreaks and Harvesters. Adults are usually under five cm and can be brightly coloured. Some larvae have an association with ants, being tended by them, on plants, or in the ant nests, even vocalizing with the ants. Apparently up to 98% of the world’s threatened butterflies belong to the Lycaenidae family.
The Ceraunus Blues are some of the smallest butterflies I have ever seen at 3/4 to 1 1/8 in (2-3 cm). They are easy to miss as they fly low over the ground, although they are widespread and common. It has taken many photographs to get these shots, they are so small and often moving, alighting for only a few moments, that it is hard to get them focused in the viewfinder. I have seen them during every visit to Mexico, no matter the time of year or location.
The light blue eggs are laid singly on the host flower buds on members of the pea family, including indigo, and partridge pea. Like other “Blues” the caterpillars are described as ‘slug-like’, these are small, oval-shaped, with a flattened underside and variably green to pinkish red. The males have stunning violet blue uppersides, which you do not often get to see; they generally alight and quickly close their wings, showing only the grey underside, with dashes and spots. Females are a dark grey on their topside with blue only at the wing bases. You will need to get right down there at ground level to appreciate these minute gossamer-winged beauties.

Cloudless Sulphur
(Phoebis sennae)
Cloudless sulphurs are beautiful, yellow, large butterflies (wingspan over 3 in or 7.5 cm) butterflies that can be found throughout Mexico, at almost any time. The eggs are laid on plants in the Pea family, Senna genus, of which there are hundreds of species, including those known as Cassia; most plants have yellow, pea-like flowers. Young caterpillars are green with a yellow stripe on each side of the length of their bodies. More mature caterpillars are yellow/orange with horizontal, thin, dark bands.
During the day, they hide in a “tent” made of their host plant leaves webbed together with silk. The adult butterflies prefer to nectar on long tubular flowers such as hibiscus. If you notice that many of the postings repeat a common theme of “found throughout Mexico or over a wide range, throughout the year” that is because I am a novice and it is far easier to spy and photograph the more common species.
To a Canadian like me, just starting the exploration of Mexican butterflies, they are all unique and beautiful. I hope you will find this journey as fascinating and exhilarating as I do.

Originally published in Mexi-Go! Winter 2014

One comment

Comments are closed.