Saturday, August 19, 2017

Insect Biodiversity in Saint Lucia

Insects comprise a significant component of the biodiversity of Saint Lucia. They can be found in almost every ecosystem and directly or indirectly affect man.

They are found living at least part, or the whole of their life cycles in both aquatic and terrestrial habitats.

There is an urgent need for the insects of Saint Lucia and their role in the island’s biodiversity to be documented. Because of changing land-use and lack of information, the existence of many species may be threatened, unknown to us. Some species may have already become extinct.

Additionally, many species have been introduced into Saint Lucia and may be considered invasive species. These species may “out-compete” local species causing them to die out eventually. Studies have not been comprehensive for various reasons including lack of trained specialists and financial resources.

Lepidoptera – butterflies, moths and skippers

Probably the best known, the larvae of this order are called caterpillars and are mainly phytophagous (plant-feeders). They are one of the most  significant plant pests of forests and agriculture. The adults are mainly nectar feeders and are characterised by a dense covering of overlapping scales and mouthparts modified into a sucking proboscis.

They are also important as pollinators of flowers.

Notes on Families

Papilionidae: Swallowtails – this group contains some of the largest and most beautifully coloured butterflies.
Pieridae: Whites, Sulphurs and Orange-Tips - medium to small-sized butterflies, many are common and the larvae feed on cruciferous plants.
Nymphalidae: Brush-footed butterflies in which the front legs are much reduced. Includes many common butterflies.
Heliconiinae: Heliconians – largely tropical group, very popular in butterfly houses and displays. Are usually avoided by predators because of distasteful body fluids. Larvae feed on species of passion flowers.
Sphingidae: Sphinx or Hawk moths – medium-sized to heavy-bodied moths with long, narrow front wings. Strong fliers, most species being active in dusk or dawn. Most feed like hummingbirds and have a very long proboscis (sucking tube mouth part).
Hesperidae: Skippers – small and stout-bodied butterflies, getting their name from their fast, erratic flight.
Sesiidae: Clear-Winged Moths – most of the wings in this group of moths has no scales. They may have a similar appearance to wasps. The larvae bore into the roots, stems or trunks of plants and can cause considerable damage.
Lycaenidae: Coppers, Hairstreaks and Blues, Harvesters and Metalmarks – Small, delicate and often brightly coloured, rapid flying butterflies some of which are quite common. The caterpillars are slug-like and they exude a honey-like secretion which is tended by ants. The ants in turn, protect them from predators and parasites.
Noctuidae: The majority of moths attracted to lights at night belong to this group. They are mostly heavy-bodied moths and are mainly nocturnal in habit. The larvae are dull-coloured and some species are serious pests of various crops.
Pyralidae: Snout and Grass moths – Members of this family exhibit a great deal of variation in appearance and habits. The melon moth larva is a pest of cucurbit crops (melons, cucumbers, etc).
Lymantriidae: Tussock moths and their relatives – medium-sized moths and are similar to Noctuiids. The larvae are rather hairy and feed chiefly on trees. They can be serious pests of forest and shade trees.
Arctiidae: Tiger Moths, Wasp Moths – (Oleander Moth) These are small day-flying moths which are wasp-like in appearance. They can be very colourful. The larva feeds on oleander plants and can be destructive in large numbers.
Geometridae: Measuring worms, Geometers – The moths in this family are mostly small, delicate and slender-bodied. The larvae are called inchworms because they appear to be measuring the leaves and twigs as they move along. When disturbed they stand erect and motionless, resembling small twigs.

Coleoptera – the beetles

Beetles form by far, the largest order of insects, with over 300,000 described and new species being discovered every year. They are characterised by the modification of their forewings into sclerotized (hardened) shields called elytra, and chewing mouthparts.

Beetles form a group with great ecological diversity, but in many families the larvae and adults share similar situations and resources.

Beetles form a group with great ecological diversity, but in many families the larvae and adults share similar situations and resources. Many are herbivorous and are well known pests of forest and agricultural ecosystems.Other families are predaceous or parasitic and are important in regulating other insects. Some feed on dead plant and animal material and are important in the recycling of nutrients bound up in organic debris.

They are also found in aquatic habitats.

Notes on Families

Passalidae: Bess Bugs – somewhat social, their colonies occur in galleries in decaying logs. Adults produce a squeaking sound when disturbed. Fairly common.

Cerambycidae: Long-Horned Beetles – most are elongate and cylindrical with long antennae. Many are brightly coloured and these feed on flowers. The dull coloured ones are usually nocturnal(active at nights). Many of the Cerambycids are wood-boring in the larval stage. A few attack living trees but most prefer freshly cut logs or weakened and dying trees and branches.

Elateridae: Click Beetles – can be recognized by their characteristic shape. The body is elongate, parallel-sided and rounded at each end. Adults are phytophagous(plant feeders) and occur on flowers, under bark or on vegetation. The larvae can be serious pests and feed on roots of crops. Some tropical species have two light-producing spots on the posterior of the prothorax (1st segment of the thorax).

Lampyridae: Fireflies – possess a “tail-light” – luminous segments near the end of the abdomen. These are elongate and soft-bodied beetles. During the day the adults are found on vegetation. The larvae are predaceous on various small insects and snails.

Scarabaeidae: Scarab Beetles – heavily-bodied, oval or elongate, usually convex beetles. These vary considerably in habits. Many are dung feeders or feed on decomposing plant or animal material. Others feed on plant material and may be serious pests of agricultural crops and lawns.

Coccinellidae: Ladybird Beetles – well known group of small, oval, convex and often brightly coloured insects. Most are predaceous both as larvae and adults. They feed on aphids, scale insects and mealybugs and are sometimes used  as a means of control insect pests in cultivated crops.

Chrysomelidae: Leaf Beetles – These beetles are largely undocumented in Saint Lucia. The adults feed principally on flowers, but the larvae may feed on leaves, some bore into stems, some into roots and some are leaf-miners(tunnel through leaf tissue).

Curculionidae – Snout Beetles or Weevils – these beetles are very common and are encountered almost everywhere. They show considerable variation in their size, shape and the form of their snout. All are plant feeders and many are serious pests. They may attack all parts of the plant. They tend to fall and “play dead” when disturbed.

Dytiscidae: Predaceous Diving Beetles – large group of aquatic beetles which are very common in ponds and quiet streams. 

Odonata – dragonflies and damselflies

Dragonflies and damselflies are among the most primitive insects. Their nymphs are aquatic predators. Dragonflies are strong fliers which rest with their wings extended laterally, while Damselflies tend to fly poorly and rest with their wings folded above their back. Adults of both groups have highly movable heads with large compound eyes. They are also predaceous on other insects.

Notes on Families

Libellulidae: Common Skimmers – most of the species in this group occur around ponds and swamps and are common. All stages are predaceous and the nymphs are aquatic. They are strong, erratic fliers.

Coenagrionidae: Narrow-winged Damselflies – these damselflies occur around streams, ponds or swamps. Most of them are feeble fliers.
Libellulidae: Common Skimmers – most of the species in this group occur around ponds and swamps and are common. All stages are predaceous and the nymphs are aquatic. They are strong, erratic fliers.

Coenagrionidae: Narrow-winged Damselflies – these damselflies occur around streams, ponds or swamps. Most of them are feeble fliers.

Orthoptera – grasshoppers, locusts, crickets and katydids

Orthopterans are medium- to large-sized insects. Many of which have elongated hind legs adapted for jumping. All females bear an external structure for laying eggs called an ovipositor. Most are plant-feeders and can be serious plant pests. Some families of these insects are among the best known insect “songsters”.

Notes on Families

Acrididae: Short-Horned Grasshoppers – Very common grasshoppers and encountered frequently. Includes the African Desert Locust which has arrived in the Caribbean on more than one occasion. The antennae are usually much shorter than the body. These insects are plant-feeders and could be destructive to vegetation. Luckily, some birds in Saint Lucia are their natural enemies.

Tettigoniidae: Long-Horned Grasshoppers and Katydids – can be recognised by their long “hair-like” antennae. Most species are plant feeding, but some prey on other insects.

Gryllotalpidae: Mole Crickets – brownish, “velvety” insects with short antennae and the front legs broad and modified for digging. They burrow into soil, where they feed on roots and may become serious pests of some crops and lawns.

Phasmatidae: Walking Sticks and Leaf Insects – the members of this family are striking in their appearance to twigs. They are slow moving plant feeders that are usually found in trees and shrubs. These insects are not usually numerous enough to do serious damage to cultivated plants.

Gryillidae: Tree Crickets – these species occur in trees, shrubs and weedy fields. Many are songsters each having its own characteristic song. They lay their eggs in bark or on stems which causes damage to twigs.

Hymenoptera – ants, bees and wasps

Hymenopterans come in a wide variety of shapes and sizes, and some are delicate and some robust. They may range from one tenth of an mm. in length, to over 5 cm.
Some are social insects and some solitary. Wings, when present are well developed and membranous.

Notes on Families

Formicidae: The Ants – a common group, well known to everyone. Probably the most successful group of insects. They occur practically everywhere in terrestrial habitats. All ants are social insects with very elaborate behavioural patterns. Their colonies may range from a few individuals to many thousands. They also nest in all sorts of places, from soil, to trees and even buildings.

Vespidae: Paper Wasps – This group used to be present in Saint Lucia but seem to be now extinct. Probably because of Hurricane Allen in 1980, whose powerful winds blew away their nests which were located in trees and under the roofs of buildings.

Pompilidae: Spider Wasps – most of these wasps are dark-coloured and have long, spiny legs. The adults catch and paralyze spiders and prepare a cell for it in the ground. They then lay their eggs on the spider which the larvae use for food.

Ichnuemonidae: The Ichneumons – a very large and important group. All its members are parasites of other insects or small invertebrates. Their larvae are internal parasites of the juvenile stages of their prey. They are wasp-like in appearance but do not sting. Many insects from this group are used in biological control programmes.

Sphecidae: These are solitary wasps. They nest in a variety of situations, either in burrows in the ground or in cavities in tree trunks or branches. They are also parasitic on other insects.

Apidae: Honey Bees, Bumble Bees and Euglossine Bees – Most of these bees are social insects and are very important because they pollinate flowers for increased fruit production and also produce honey which is consumed by humans.

Hemiptera – true bugs

Hemipterans are a diverse group of insects unified by several consistently shared characteristics:

  • They all have piercing-sucking mouthparts and most species have 2 pairs of wings.
  • The young are similar to the adults in appearance except for developing wings and sex organs, and they share the same habitat.

Although they are primarily a terrestrial (living on land) group, some are adapted to an aquatic life style. The group is composed primarily of plant sap feeders and some are serious pests of cultivated plants. Other families are predaceous on other insects and are beneficial to man. A few species are blood-feeders that attack man and other animals and some of them transmit diseases in the process.

Notes on Familes

Pentatomidae: Stink Bugs – are the most common and abundant of the bugs that produce a disagreeable odour. Some are plant feeders, others feed on insects and some on both. Some of these species may be serious plant pests.

Coreidae: Leaf-footed bugs – the majority of this group are plant feeders, but some are predaceous. Some species have the hind legs expanded and “leaf-like” in appearance.

Reduviidae: Assassin Bugs – This is a large group of predaceous bugs which are usually blackish or brownish in colour. Most species prey on other insects, but a few are blood-sucking and will bite humans and other animals.

Rhophalidae: Scentless Plant Bugs – These bugs lack scent glands and are small and light-coloured. They occur principally on weeds and all are plant feeders.

Belostomatidae: Giant Water Bugs – This family contains the largest bugs in the group. Fairly common in ponds, where they feed on other insects, tadpoles and small fish. They fly about and may be attracted to lights at night. They can inflict a painful bite if carelessly handled.

Berytidae: Stilt Bugs – These bugs are slender and elongate with long legs and antennae. Sluggish insects, they occur on vegetation and feed on plants.

Isoptera – termites

All termite species are social insects, composed of a limited number of reproductives (with the ability to mate), numerous wingless workers, soldiers and immatures. Most feed on materials high in cellulose which is broken down by symbiotic protozoans haboured in their digestive tract. They are extremely economically important as pests of wooden structures and occasional plant pests. They also play an important role in the building of tropical soils by breaking down old, dead and dying trees.

Notes on Families

Termitidae: Termites – includes several species, the main characteristic is that their nests, through specially built tunnels,  always maintain contact with the ground. This helps to maintain moisture levels. They are also called subterranean (underground) termites.

Blattodea – roaches

Roaches are largely tropical and subtropical omnivorous insects and mostly live in the forests. Some species have become domesticated in temperate regions. Most are nocturnal, terrestrial species that rarely use their ability to fly. Many are gregarious, occuring in groups consisting of both adults and nymphs of various ages. Several species establish themselves in man’s dwellings, where they contaminate foodstuff with their excreta and are recognized as household pests.

Notes on Families

Blattidae: Cockroaches or Roaches – common insects in Saint Lucia, especially the American Cockroach (Periplaneta americana) which invades households.

Blatellidae: Tree Roaches – mainly live on trees, leaf litter or debris in the forest. One species, the German Roach (Blatella germanica) invades homes and businesses and can become a very serious nuisance.

Homoptera – whiteflies, scale insects, leafhoppers, aphids, mealybugs

An extremely diverse group little documented in Saint Lucia, all species are phytophagous and many are serious plant pests. They are common in that all have piercing-sucking mouth parts and some transmit toxins and plant diseases from plant to plant.

Notes on Families

Aphidae: Aphids or Plant Lice – A large group of soft-bodied insects which are frequently found in large numbers, sucking sap from the stems or leaves of plants. This family contains a number of serious pests of cultivated plants.

Coccidae: Soft Scales or Wax Scales – Females are elongate-oval, usually convex but also flattened, with a hard, smooth exoskeleton or covered with wax. The males may be winged or wingless. A number of species are serious pests in cultivated crops, greenhouses and homes.

Pseudococcidae: Mealybugs – the name is derived from the waxy secretions that cover the bodies of these insects. The body of the female is elongate-oval and segmented. Some species lay eggs and others bear live young. The males, if any, are winged. Mealybugs may be found on any part of the host plant and some are serious pests, attacking a variety of plants.

Diptera – The Flies

This is a large and diverse group of insects. A few are wingless, but the adults are characterised by one pair of wings.  Adults and larvae may be found in a wide variety of situations (from terrestrial to aquatic) and they can sometimes occur in enough numbers to become a nuisance. Some are important as vectors of diseases of humans and animals, while others are important as scavengers.

Notes on Families

Muscidae: A large group of flies in which many are serious pests in some parts of the world. The most famous is the House Fly (Musca domestica). It breeds in filth of all kinds and is very abundant. It can be a vector or several diseases including typhoid fever, dysentery and some forms of “red-eye”.

Calliphoridae: Blow Flies – can be found almost everywhere. Some species are of economic importance. They are usually metallic blue or green in colour. Most species are scavengers, living on dead animals and excrement. Others like the Screw Worm Fly, lays its eggs in wounds or the nostrils of animals, where it may become a serious pest.

Teprhitidae: Fruit Flies – small to medium-sized flies usually with attractively spotted or banded wings. Adults are found in flowers but the larvae feed on fruits and are often serious pests throughout the world. The locally found species feeds on mainly on plums and guavas.

Ottitidae: Picture-Winged Flies – small to medium-sized flies with marked wings and their bodies shining and metallic. Usually found in moist places and are abundant. Little has been documented about their larval stages.

Stratiomyidae: Soldier Flies – These flies are medium sized or larger and are usually found on flowers. The larvae may be found in several habitats. Some are aquatic and feed on algae, some on decaying materials and others occur under bark.

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