Natural Enemies of Butterflies

Natural Enemies of Butterflies

All stages of butterflies except the adult are attacked by natural enemies like parasites and diseases . The parasites belong to the insects orders , Hymenoptera (wasps,bees, ants) and Diptera (flies ) . Among them , members of Ichneumonidae , Braconidae and Chalcidoidea (hymenoptera) and Tachinidae ( Diptera) are endoparasites . The hymenopterous parasites lay their eggs in the larvae of butterflies by piercing the host’s skin with their sharp ovipositor. Then, a large number of eggs are laid in each host. The eggs of parasites hatch and feed on the internal tissue of the host which results in the death of butterfly larva. The fully developed parasite larve hatch and feed on the internal tissues of the host which results in the death of the butterfly larva. The fully developed butterfly larvae then come out of the host and pupate on or near the dead butterfly larva in bright yellow cocoons from which the adult parasites eventually emerge . The dipterous parasites mostly lay eggs or occasionally young larvae on the food plant of the butterfly larvae. The parasites attach themselves to the host larvae and then burrow into their tissues .

Mites acts as ectoparasites . They live on the outside of the butterfly host and suck the body fluids . Bacterial and fungal diseases also cause mortality of the butterflies in high humid areas .

Predators

Both caterpillars and adults are predated upon by vertebrates , birds , lizards ,bats, insectivorous and monkeys are important predators . Spiders , preying mantids , robber files , assassin bugs , phymatid bugs , tiger beetles , ground beetles , wasps, ants, myriapods and scorpions are some of the invertebrate predators . Birds like the Paradise Fly –catcher , Drongos , Bee –eaters , Ashy Swallow Shrikes and Wood Swallow Shrikes regularly prey upon butterflies that are on the wings. Among the spiders , thomisids lie in wait on flowers , aranacids spin webs and large oxyopids hide in bushes to catch the butterflies .

Protection From Natural Enemies

Egg

Butterfly eggs are protected from their natural enemies on account of the small size , color and placement , mostly on the underside of leaves.

Larva

Newly hatched larvae are very minute and the predators usually avoid hunting them . As they grow , they develop spines and long hairs for protection . Some mimic the leaves or resemble the buds and twigs of host plants . They also escape by resembling objects that are unattractive to the predators . For example , young larvae of Papilio demoleus resemble bird droppings and are not touched by predators even though they are present on the uppersurface of leaves during this stage . Nymphalid larvae are spiny and brightly coloured . Some larvae deter their predators by their obnoxious smell or unpleasant taste. Larvae of the Papilionidae have a gland called Osmeterium just behind the head. When the larvae is disturbed , osmeterium is everted , emitting a strong odour which repels the predators . It is also aposematically colored to deter the natural enemies .

Grown up larvae oftern mimic their sourroundings to escape from the predators . They resemble the part of the host plant to a remarkable degree and oftern change their color . Ocelli are employed by some species of Papilionidae to startle their enemies . Skipper larvae hide themselves in leaf rolls or tubes .

Pupa

Pupae are mostly cryptically colored or placed in inconspicuous positions on low growing plants or in cocoons . Many pupae are remarkably well protected by their color and forms . For example , the pupae of the Orange tips resemble seed-pods and those of the Vanessidi often resemble a withered leaf both in shape and color. Pupae of certain Lycaenidae resemble bird droppings and a few resemble the head of a monkey .

Adult

Many adult butterflies blend themselves into their background or become cryptic . They may camouflage themselves with leaf like patterns and shapes as in the leaf butterflies of the genus kallima . When at rest , both wings look like a dry dead leaf with large elliptical leaf shape complete with stalk , mid rib , worm holes and patches of mould , thus duplicating a dry decaying leaf.

Such cryptic patterns may appear on the uppersurface in members of Nymphalidae. In such cases , the wings are held flat on the surface of the bark . In ground resting butterflies , shadows falling on the ground may nullify this advantage . So when resting , many Satyridae orientate themselves towards the sun to eliminate the shadows or tilt their bodies and wings towards the sun to reduce the shadows size.

Butterflies with transparent wings are usually found in forests . They merge with dappled light and shade by flying close to the ground and settling frequently . Since they are almost entirely transparent , the natural back ground is visible through the wings and the butterfly itself is difficult to distinguish . Another protective device is the use of patterns which draw the attention of a predator away from the vital parts of its potential prey . Eye spots or ocelli in the wings of the members of Satyridae , Brassolidae , Morphidae and Amathusidae serve as deflecting patterns for potential predators such as birds. These predators will take a swift peck at a prominent eye spot rather than some more vulnerable parts of the body and the butterflies survive to live with damaged wings .

In members of Lycaenidae , the ocelli combine with fine tail at the rear inner angle of hind wings to produce a ‘false head’. When these butterflies twist their tails, they resemble the moving antenna of the false head . Such Lycaenidae escape from bird peckings with the loss of that portion of wings alone. Butterflies with eye spots markings or other striking color patterns may also gain protection by startling their enemies with sudden movements that reveal their colors . At rest , such butterflies are drab colored and inconspicuous but when disturbed , they open the wings suddenly to reveal the vivid markings or huge eye spots to shock the predators .

Adult butterflies also employ mimicry to gain protection . Certain butterflies are unpleasant , unpalatable or inedible to predators such as birds and other vertebrates . Such species are patterned with warning colors and thus are easily recognized and avoided by the predators . Hence ,other harmless and quite palatable butterflies have acquired similar color patterns and so derive protection because predators mistake them for unpalatable species and leave them alone . The unpalatable species are normally referred to as models while the palatable species that resemble them are called mimics

Mimicry is either Batesian in which there is an unpalatable model species and a palatable mimic or mullerian in which two or more unpalatable and often unrelated species have evolve the same color pattern .

The family Danaidae include many distasteful species and thus supplies the models for many of the classic examples of the Batesian mimicry by members of other families . The plain Tiger , Danaus chrysippus chrysippus is a model for the female of the Diadem, Hypolimnas misippus ( Nymphalidae ). In mullerian mimicry , both the model and mimic have equal advantages . The common Indian examples are again in the Danaidae: the crows and the Tigers and the Windmills etc.,and to a certain extent , the Sailers and the Sergeants are also the Mullerian mimics.

Butterfly Conservation