Hairstreaks and Blue Butterflies Lycaenidae Lycaenidae is a large, worldwide family are dumpy and have a silken girdle which of small butterflies with over six thousand usually holds the ventral surface close to described species. This is about one-third the substrate, unlike pupae in the preced­ of the total of all known butterflies. Ten ing families which are suspended head species have been recorded from the Cay­ downwards from a silk pad by a hooked man Islands, and these represent the two organ (cremaster) at their posterior ends. major subfamilies, Theclinae (Hairstreaks) Adult Lycaenidae have six functional and Polyommatinae (Blues). In Blues legs in females, but in males the front there is generally considerable sexual di­ pair are reduced and not used for walk­ morphism in wing colour, but the sexes ing. They usually perch with wings closed, of Hairstreaks are usually rather similar. and the settled butterfly will slowly raise Caymanian Theclinae, with the exception and lower its hindwings against the fore­ of Eumaeus atala, have one or two tails wings. Such movement may enhance the on each hindwing, but the four Cayma­ head-like appearance of the tarnal area nian species of Polyommatinae have at on the under side of the hindwing, with its most only rudiments of tails. eye-spot markings and antenna-like tails. Polyommatinae are low-flying butterflies This illusory head is thought to attract a found mostly in open, grassy and flowery hunting bird or lizard, so that its attack is situations. Very few show any tendency to drawn to the relatively expendable hind­ migrate, so that island populations can be wing tarnal area and deflected from more long isolated and hence are often distinc­ vital body parts. tive (Nabokov 1945). The great majority use herbaceous Fabaceae (Leguminosae) as larval food-plants, and their slow­ Atala Hairstreak moving, woodlouse-shaped caterpillars of­ ten feed in the flower heads. Blue Butter­ Eumaeus atala (Poey, 1832) fly larvae are frequently attended by ants Plate Ill (7 -9) in a symbiotic relationship in which the caterpillar receives some protection from Recognition arthropod predators and probably para­ FWL 17-22 mm. (males smaller than fe­ sitic wasps, and the ant in return receives males). Unlike other Hairsteaks, the wings a sweet, sugary secretion from glands on of Eumaeus atala are rounded, and there the caterpillar (Pierce 1984). are no hindwing tails. The upper surface Theclinae tend to be more associated has a black ground colour with blue (male) with wooded areas and bushy places, of­ to green-blue (female) iridescent scaling ten flying about the tops of trees, but this on the forewing except on the veins and is not true of Strymon istapa, the com­ broad margins; there are basal patches of monest of the Cayman Hairstreaks. the same colours on the hindwings which Pupae in both subfamilies of Lycaenidae also bear a marginal series of green-blue 67 spots. The under surface is similar in both sexes, the forewing entirely black, the hindwing with three arcs of iridescent blu­ ish spots in the distal half and a bright red spot at the centre of the inner margin. The abdomen is red. Altogether the Atala is a striking butterfly which is unlikely to be mistaken for any other Caymanian insect except perhaps, at a distance, the Faithful Beauty moth (page 159). Subspecies Only the nominate subspecies Eumaeus atala atala occurs in the Caribbean. Populations in Rorida were named as E. a. florida Rober, 1926, but this is poorly differentiated from the typical form. Species' range Reared female Atala, CB (30.i.2008), RRA The species is restricted to Rorida, the Bahamas, Cuba and the Isle of Pines, and Cayman Brae. In Rorida it is a very lo­ cal butterfly and appears to exist in rather Cayman Islands distribution temporary colonies in which the butter­ Cayman Brae flies may be plentiful for a time and then die out. Habitat Eumaeus atala is nearly always found close to cycads (Zamia) on which the larvae feed. On Cayman Brae it is most Male Atala, CB (28.i.2008), RRA numerous in dry woodland on the bluff. Zamia grows on all three Cayman Islands, but to date the Atala has been seen only on Cayman Brae. History The Atala Hairstreak was discovered in large numbers on Cayman Brae in No­ vember, 1990 (Miller & Steinhauser 1992). It was found at Stake Bay on the north coast, Hawkesbill Bay on the south coast, and was also seen at Brae Reef Re­ sort. It now seems to occur wherever its food-plant grows, but the main popula­ tion appears to be on the central bluff. 68 .