Insects comprise the largest number of organisms found all over the world. They dwell in all sorts of habitats ranging from high mountain peaks to the desert areas. The body shape as well as the overall anatomy of insects is greatly modified so as to meet the demands required to adapt to a particular habitat. Epilachna is one such elegant beetle belonging to kingdom Animalia and phylum Arthropoda. Its class is Insecta and order is Coleoptera. Epilachna is commonly known as ladybird beetle belonging to the family Coccinellidae and subfamily Epilachninae. There are different species known for this genus and each carries a particular sculptured pattern of spots over the elyra. The species are classified on the basis of number of spots present over the elytra.
Epilachna is commonly known as the Mexican bean beetle or the Hadda beetle is presently recognized as an important agricultural pest. It is an herbivorous insect that feeds on plants as compared to other ladybird beetles that feed on insects. It is widely distributed throughout the oriental regions. It fails to survive in the dry regions. It resembles other lady bird beetles and the number of spots vary from 16-22 over the dome-shaped elytra. Overall colour is highly variable ranging from bright red to rusty brown to golden yellow depending upon the species as well as on the ecological conditions. The body may measure 6-7 mm in length. The beetles are active from May to August in the hilly areas while in the plains they are active from May to September. In winters they undergo diapauses under the, cracks or crevices in soil.
Eggs are yellow measuring 1.3 mm in length and the female prefers to lay eggs in clusters on the underside of the leaves. The number of eggs in an egg cluster may reach up to 75. Eggs hatch into tiny larvae which are yellow in colour, spiny and are pill-shaped. The newly hatched larvae are about 1.5 mm in length and may reach to a length of 1 cm before they undergo pupation.
Hadda beetle is a polyphagous pest feeding on a number of agricultural crops as well as some wild plants. The adults generally prefer to feed on the leaves of the plants but may also feed on the flowers as well as on the fruits. The adults as well as the larvae feed on the tender parenchyma present on the underside of the leaves and leave the epidermis of leaf intact. The leaf eaten by these beetles look like skeletonized in appearance. The larvae are voracious feeders and cause more damage than the adults as they require more food to complete the development as soon as they can. Fully grown or the last instar larvae attach their anal segment to the underside of the leaves and then they undergo pupation.
Pupae are yellow in colour with white margins on the dorsum. Its anterior portion is smooth while posterior margin is spinous. Pupal period lasts for few days in summers but it is prolonged in the winters to 1-2 weeks in the winters. The whole life cycle is completed in 15-54 days. The adult survives for about 4-6 months. About 7-8 generations of Hadda beetle occur in plains and 1-2 generations in hills in a year.
The beetles cause considerable damage to the plants belonging to the family Cucurbitaceae and can be controlled by chemical insecticides like malathion. During the months of March a number of parasitoids have been reported to infect these beetles so during this period spraying of insecticides should be avoided.