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Eunica Bechina is a butterfly in the family Nymphalidae that can be found in the savanna in the cerrados of Central and South Brazil. This butterfly chooses Caryocar brasiliense as its hostplant and larvae are found in highest concentration during September and October, the months when C. brasiliense leaves are at their most tender, which is preferable for the consumption of the caterpillars. A number of species of ant also occupy this plant and are antagonistic to E. bechina larvae, attacking and removing them from the plant. Because of this, the females of this species preferentially select plants with noticeably less ant infestation. The caterpillars of this species have developed defensive strategies to avoid predation such as regurgitating when they are bitten by the ants, leaping from the leaf and suspending themselves from a silk thread, and exhibiting a beat reflex.

Eunica Bechina
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Lepidoptera
Family	Nymphalidae
Subfamily:	Biblidinae
Genus:	Eunica
Species:	Eunica bechina

Geographic range

E. bechina is found in the Andes, the Amazon Basin, the Amazon Valley, and throughout the Neotropical region. Primarily, the species is found in the cerrados of Central and Southern Brazil and is most common in the Brazilian state of São Paolo.

Habitat

E. bechina is commonly found in the cerrados of Brazil, a large tropical ecoregion primarily composed of savannas, found in the Brazilian states of Goias, Tocantins, Minas Gerais, São Paolo, and Mato Grosso. Within the cerrado, the butterflies are primarily found in the neotropical savanna region with high concentrations of shrubs and trees.

Food resources

Caterpillars and larvae

E. bechina uses Caryocar brasiliense as its host plant. This plant, native to the Brazilian savanna, has extrafloral nectaries on its sepals and leaf buds and is visited throughout the day and the night by a variety of ant species that are considered nectar gatherers. Butterflies preferentially lay their eggs on younger C. brasiliense plants which have fewer ants, as caterpillars prefer to feed on young leaves and ants will attack and remove E. bechina larvae from the plants. First to fourth instar larvae construct frass chains on these leaves. When agitated, the caterpillars leap from the plant and suspend themselves from the leaf with silk threads.

Adult diet

E. bechina, similar to other fruit feeding nymphalids, feed on tree sap from a variety of trees in the Brazilian savanna as well as on decaying fruits and mud puddles.

Parental care

Oviposition

Female E. bechina lay their eggs on small, young leaves of shrubs of C. brasiliense, most commonly between 10 AM and 1 PM. Eggs of this species are found primarily on young leaves, followed in probability of distribution by shoot tips, petioles, and stems. The eggs can be found anywhere between 3 to 150 centimeters above the ground, and on average were found around 60 centimeters high. Eggs hatch around 5 days after oviposition. Larvae of E. bechina are present in greatest numbers on C. brasiliense in September and October when most of the leaves on the plant are young, soft, and primarily red in color. However, larvae of this species are found on their host plant at all times during the rainy season in the Brazilian savanna, which occurs from September to January. While growth from egg to the fifth instar occurs on the C. brasiliense plant, pupation typically occurs on neighboring shrubs.

Life history

Life cycle

The life cycles of E. bechina are divided into four main stages: eggs, larvae, pupa, and adults. The eggs hatch after 5 days, the larval stage lasts approximately 17 days, and the pupal stage lasts 9 days.

Eggs

E. bechina eggs are yellow, cone-shaped, flat at the top, and measure approximately .76 mm in height and .72 mm in diameter. They have between 12 and 14 longitudinal ridges and between 10 and 12 transverse ridges. Eggs hatch around 5 days after oviposition.

Larvae

First instar larvae of E. bechina, lasting 2.6 days, have translucent brown heads, translucent yellow legs, and translucent yellow bodies that turn pale red after they feed because of the external visibility of their intestines. They reach a maximum of 3 mm and have an average head width of .42 mm.

Second instar larvae, lasting 1.5 days, have black heads with two stubby horns and a pale brown body with short, conical scoli. During this stage, they reach a maximum length of 6 mm, an average head width of 0.67 mm, and an average horn length of 0.33 mm.

Third instar larvae, lasting 2.4 days, have dark brown bodies and black heads with white warts and two long, diverging horns with accessory spines in the middle and a knob crowned with short spines at the end. They reach a maximum length of 12mm, have an average head width of 1.26 mm, and an average horn length of 2.36 mm.

Fourth instar larvae, lasting 3.7 days, have a similar head to the third instar larvae and a dark brown body with a light brown stripe. These larvae reach a maximum length of 20 mm, have an average head width of 1.95 mm, and have an average horn length of 4.56 mm.

Fifth instar larvae, lasting 6.33 days, is the last of the caterpillar stages of E. bechina before pupation. During this stage, the head remains the same as the third and fourth instar and the body is brown with a dark brown back with white lines and stripes. The underside of the caterpillar is yellow, orange, or red with pale yellow or orange stripes. It has dark brown legs and red anal prolegs. During this stage, the caterpillars reach a maximum length of 40 mm, have an average head width of 3.28 mm, and an average horn length of 6.62 mm.

The prepupae of E. bechina forms a J shape and is adhered to its substrate by its anal prolegs and silk.

Enemies

Predators

Ants are attracted to C. brasiliensis, E. bechina's larval host plant, because of its extrafloral nectary secretions. When E. bechina caterpillars are not on their established frass chains at the edges of the leaves, they interact antagonistically with the ants who attempt to climb onto the plant. In these situations, the larvae are often attacked by foraging ants, which can result in the death of the caterpillars. Interestingly, the ants who predate E. bechina are known to tend larvae of the families Lycaenidae and Rionidae. One species of Azteca ant and two of Camponotus, C. crassus, and C. aff. blandus are most aggressive towards the caterpillars. Camponotus ants are large and able to carry caterpillars off the plant alone while the Azteca ants are small and recruit a hoard of nestmates to assist them. Other predators of E. bechina include two species of Crematogaster, two species of Pheidole, one of Pseudomyrmex, and Ectatomma tuberculatom.

Response to predation

E. bechina caterpillars regurgitate and bleed when they are bitten by ants. This behavior most often repels the predator who, as a result of this behavior, abandons the larvae. When ants bite multiple times, they display disturbance behavior, cleaning off their mandibles, antennae, and head, walking erratically, and shaking their bodies. The caterpillars also demonstrate defensive behaviors against the attacks of the ants by suspending themselves off the C. brasiliense leaves by silken threads, a defensive method common to arthropods who live near antagonistic ant species. They exhibit a beat reflex in which they rear their bodies, curl, and wriggle intensely. This can intimidate and deter some of the ants who invade the plant, most often when used by the larger, late instar larvae, but can also further attract predators. Additionally, E. bechina caterpillars use the frass chains they construct to decrease their risk of predation and removal by ants. Ants do not climb this structure, so caterpillars can rest and take refuge on these structures.