Leaf Beetles

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Rank & taxon

Family Chrysomelidae

Description

The vast majority of leaf beetles that are considered pests of palms belong to the Hispinae subfamily of Chrysomelidae and are leaf miners. Adult leaf beetles range from 3-35 mm in length and are elongate or oval to orbicular in shape. They are glabrous, often colorful, and the elytra typically have longitudinal ridges alternating with rows of pits. The antennae are generally less than half the length of the body, filiform, and typically held in a V position. The tarsi of this family generally appear to have four tarsomeres, but actually have five; the fourth segment is usually hidden by the lobes of the third. Notably, in the Hispinae, the fourth segment is fused to the fifth, so there actually are only four tarsomeres. Hispine larvae are dorsoventrally flattened with prognathous mouthparts, as compared with other chrysomelid larvae which are elongate and curved, with a deflexed head.

Distribution

Worldwide, over 2,500 genera and 35,000 species (subfamily Hispinae represents 170 genera and 3,000 species worldwide, primarily restricted to tropical and subtropical habitats)

Biology/life cycle

Chrysomelids are strongly associated with plants, and are therefore primarily terrestrial. Nearly all members of the family are phytophagous, and many are considered pests. Leaf beetles are usually highly host-specific. Members of the subfamily Hispinae are almost exclusively found on monocotylendous hosts, with many having a strong preference for palms. Adult females typically lay a relatively small number of eggs in a small cavity created for the purpose, and cover it with a cap or shield of fecal matter or plant fibers. When the larvae hatch, they enter the leaf through the cavity, and typically go through three instars before pupating. Hispine larvae, as leaf miners, feed between the epidermal layers of the leaf, forming galleries, or leaf mines. Adults typically feed on the leaves as well, often preferring younger leaves.

Hosts

Palms: a wide variety of palms, including Cocos nucifera (coconut palm) and Elaeis guineensis (African oil palm)

Other: subfamily Hispinae may be found on a wide variety of other monocotyledonous hosts but is rarely found on dicotyledons; the other subfamilies may be found on a variety of dicotyledonous plants

Representative taxa on palms

The coconut leaf beetle (Brontispa longissima) is one of the most damaging pests on coconut palms (Cocos nucifera), but may also infest over 20 other species of palm. It feeds on young leaves, causing damage to seedlings as well as mature palms. It is a serious pest in coconut palm growing regions throughout the Pacific.

The palmetto tortoise beetle (Hemisphaerota cyanea) occasionally causes feeding damage on palms in the southeastern US, particularly saw palmetto (Serenoa repens). The larva extrudes a dense frass shield to protect itself from predators.

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