Smallest Cayman butterfly is blue

Grand Cayman Pygmy Blue

Brephidium exilis thompsoni

The Pygmy Blue is a Grand Cayman endemic subspecies, found nowhere else in the world!

It was first discovered by scientists in 1938 and was not documented again until Dr. R. R. Askew’s visit in 1985, when two colonies were located on the north and west coasts.

In 2002 a colony was also found at Midland Acres.

The scientific name of a butterfly can have two or three names: the genus, the species and sometimes a subspecies. For example, the scientific name of the Cayman Pygmy Blue butterfly is Brephidium exilis thompsoni.

It was named after Gerald Thompson, one of the young Oxford University students who discovered it in 1938 on the Oxford Expedition to the Cayman Islands.

This tiny butterfly is one of the smallest butterflies in the world! Thank you to Ann Stafford for her research on native plants and wildlife in the Cayman Islands and her efforts to promote their importance and protection; photographs by Frank Roulstone.

The Pygmy Blue is found in the United States, northern South America, the Bahamas, Cuba, Jamaica, Hispaniola and the Cayman Islands.

Brephidium exilis isophthalma is the subspecies found in the Bahamas, Cuba, Jamaica and Hispaniola.

The subspecies found here is different from all others and is found only on Grand Cayman.

The females are larger than the males and not as blue. The wingspan of this tiny butterfly is 3/8 inch – ¾ inch (1-2cm).

The Pygmy Blue is found only in salt-marsh areas where its larval food plant, the plant its caterpillar eats, Glasswort, Salicornia perennis, is abundant.

The Pygmy Blue also depends on the little pink flowers of Sea Pulsey (Sesuvium portulacastrum) as a source of nectar for the adult butterfly.

Glasswort (Salicornia perennis), is a waxy-leafed succulent tolerant to salt concentration, has a light green color, and is characterized by having multiple branching.

The glassworts are small, usually less than 30 cm tall, succulent herbs with a jointed horizontal main stem and erect lateral branches. The leaves are reduced to scales, so the plant appears to be leafless.

The hermaphrodite flowers are wind pollinated, and the fruit is small and succulent and contains a single seed.

Sea Pulsey has attractive small white to purple or pinkish flowers and grows on the edges of swamps or beside marl roads.

It is locally abundant and is a superb, mat-forming, creeping seaside plant in coastal areas. It helps stabilize shorelines and dunes and is great and very useful for preventing erosion. It has thin, short, leathery leaves that are edible.

It is native throughout much of or all of the Caribbean and Bahamas. It is also found throughout tropical and subtropical shorelines and coastal areas worldwide.

Protect Cayman trees and encourage Cayman Wildlife! For more information, to share your knowledge or if you would like to get involved with the many activities in the National Trust’s Know Your Islands Program, please visit or call 949-0121.

Last week’s answer: The primary offender causing sea itch is the larvae of the thimble jellyfish.

Trivia question: What is the simplest of the multicellular marine animal that comes in many shapes, sizes, and colours including purple, yellow and red?

Look for the answer in next week’s column.

The weekly column from the National Trust is submitted by Marnie Laing, Education Programs Manager at the Trust. The Trust can be contacted at 949-0121 or via email at [email protected].

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