common name: cassius blue, tropical striped blue
scientific name: Leptotes cassius (Cramer) (Insecta: Lepidoptera: Lycaenidae: Polyommatinae)

Introduction - Distribution - Description - Life Cycle and Biology - Hosts - Selected References

Introduction

The cassius blue, Leptotes cassius (Cramer), is a beautiful tiny butterfly that is locally common throughout peninsular Florida — particularly along the coasts. It is sometimes known as the tropical striped blue (Scott 1986). There are two subspecies in the United States, theonus in Florida and striata in Texas. Blues in the genus Leptotes are collectively known as the "zebra blues" (Brower 2008) because of the characteristic dark stripes on the under surface of the wings.

Distribution

The cassius blue, Leptotes cassius theonus, is resident in southern peninsular Florida but occasionally strays to more northern areas. It is cold sensitive and cannot survive even the winters of northern Florida. The mechanism by which individuals arrive at more northern localities is not known. Perhaps some are carried by wind. Daniels (2005) found larvae on ornamental leadwort plants in South Carolina that had been shipped from Florida and suggested that piggybacking on ornamental host plants may account for the some of the northern strays.

Description

Adults: The average wing spread of adults is approximately 1.2 cm. (slightly less than one half inch) (Opler and Krizek 1984). The undersides of the wings are striped with two eyespots on the margin of each hind wing. Males are pale to bright blue above. Females are bluish-white to white above on basal areas of wings with broad dark borders on the front wings and a dark spot on the rear margin of the hindwing (Cech and Tudor 2005, Minno and Minno 1999).

adult - dorsal view

adult - ventral view

Eggs: The eggs are whitish-green and the surface is sculptured with a network of knobs and ridges.

egg

Larvae: Full grown larvae are approximately 0.5 inch in length (Minno et al. 2005). Body color is green with faint dark markings or patterned with faint white markings (formed by numerous tiny white hair-bearing tubercles [chalazae]) or red markings and white chevrons.

larva

Pupae: The pupae are tan with dark markings and numerous short white hairs.

pupa

Life Cycle and Biology

The cassius blue is found throughout the year in Florida and has at least three generations per year (Glassberg et al., Minno et al. 2005).

The eggs are laid singly on the flower buds of the host plants and larvae eat the buds, flowers, and developing seeds (Minno and Minno 1999, Minno et al. 2005). There are four larval instars in Florida (Downey and Allyn 1979).

The larvae are well-camouflaged and may be attended by ants for which they provide sugary secretions from a honey gland on the dorsal surface of the seventh abdominal segment (Downey and Allyn 1979, Opler et al. 2009).

As is the case with most lycaenids, pupae stridulate with a scraper and file in the dorsal cleft between the fifth and sixth abdominal segments (Downey and Allyn 1979). The stridulation is assumed to serve a defensive purpose.

Downey and Allyn (1979) found a braconid wasp in the genus Pelecystoma parasitizing larvae, and the tachinid fly Eusisyropa boarmiae [Coq.] parasitizing pupae. In a collection of eggs from early June, they found 17% parasitized by the generalist egg parasite Trichogramma minutum Riley.

Adults feed on nectar from a wide variety of flowers.

Hosts

The larval hosts of the cassius blue are a variety of vines, shrubs, and trees in the pea family (Fabaceae) (Minno and Emmel 1993, Minno and Minno 1999, Minno et al 2005) including the:

Selected References

Authors: Donald W. Hall and Jerry F. Butler, University of Florida
Photographs: Jerry F. Butler and Donald W. Hall, University of Florida
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-460
Publication Date: June 2009
Copyright 2009 University of Florida

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