Insects are the animals dwelling on the planet earth well adapted to survive in all sorts of environments one can imagine. They can survive under conditions of extreme cold, deserts and hot areas. They are arthropods whose number is largest when compared with all animal species. They are gifted with dynamic adaptations that help them to occupy all the available habitats. The body of insects is divided into three parts namely, head, thorax and abdomen bearing different appendages for carrying out different functions. Although the body organization appears simple but it is complex when studied in detail. Head bears compound eyes adapted for mosaic vision as well as antennae which are chemosensors, detecting chemicals present in the environment. The head also bears mouth with mouth parts adapted for chewing, biting, sucking, lapping or piercing etc. Thorax typically bears either single or two pairs of wings which are named either fore or hind wings. The thorax also bears three pairs of legs adapted for walking, swimming, burrowing or digging depending upon the habitat of insect. Abdomen bears reproductive structures and it may be terminated into an ovipositor or sting. All the insects have been placed in the class Insecta which has been further divided into a number of orders and suborders depending upon the characters of the insect.
Insects are very beneficial creatures as they maintain the ecological balance. Some are economically useful as they provide us with useful materials like silk, honey or lac. Some are notorious and their presence annoys us, some act as carriers of diseases while some are known to damage our agricultural crops resulting in heavy economic losses. Ladybird beetles are known as farmer’s friends but some have acquired the status of pest damaging the nightshades and cucurbits. They are placed in the family Coccinellidae and order Coleoptera due to the presence of elytra which are the modifications of the fore-wings and thus, provide protection to the delicate, membranous hind-wings. Henosepilachna vigintioctopunctata is one of the most important pest species of the subfamily Epilachninae. It is commonly known as 28-spotted ladybeetle or Hadda beetle which was previously known as Epilachna vigintioctopunctata. It is known to damage the foliage of potato and other allied plants and has got its origin far east of Russia. The members of the subfamily Epilachninae are so similar in their size and appearance, habit and habitats, distribution and other aspects that they have always confused the researchers both in literature as well in the museum specimens.
The body of the hadda beetle is about 7 mm long, round, convex and glossy. The color of the beetle is reddish-brown bearing thirteen small spots on each elytron and one spot each on either side of the thorax. The beetle undergoes complete metamorphosis. The life history comprises of egg, larva, pupa and adult. The mature female after mating lays eggs in clusters on the underside of the leaves. Each egg cluster consists of ten to seventy eggs but the egg-laying efficiency of the female is very much dependent upon the food quantity as well quality. Food is known to provide energy to carry out the vital activities of life. The anatomy as well as the physiology of the female is relatively complex in comparison to that of the male as she has to lay eggs that will be responsible for the progression of the race. The eggs measure about 1.5 mm and are yellow colored and do not turn orange before hatching. The eggs hatch in 4-5 days depending upon the climatic conditions into tiny yellow-colored larvae provided with spines over their bodies. With every moult the spines become tough and conspicuous and their exact function is defence from the enemies. The larvae feed on the epidermal tissue of the leaves of the host plant. The third and the fourth instars are the voracious feeders as they are under peer pressure to enter pupation.
The leaves damaged by the larvae show only veins and therefore, the beetles are also known as leaf scrapping beetle. The fourth instar after attaining full growth enters pupation. The pupation is yellowish-brown with black spots and bristles at the posterior end while the anterior end is smooth. The pupal period is also influenced by the climatic conditions but under favorable conditions it is completed in 7-8 days. The newly emerged adults are very delicate and are bright yellow in color without any spot. The adult pulls itself out of the pupal case and then rests over it as its elytra as well as wings are very delicate and it can be easily attacked by the enemies. Body mechanisms come into action and after few hours spots appear over the elytra and it begin to become hard. After the appearance of spots and hardening of the elytra the adults start feeding of the leaves of the host plant. The adults attain full sexual maturity in about 10 days and then begin to mate and the life cycle continues again. Adults are also known to hibernate during winter under the fallen leaves or other protective places and do not reproduce but with the advent of favorable conditions reproductions begins again.
They are distributed world-wide but believed to have originated Far East of Russia. Their range extends throughout India, Pakistan, China, Japan, Southeast Asia and Oceania. In 2010 hadda beetles were also obtained from New Zealand. The total damage caused by these pest beetles varies according to the regions and may reach about 25%. A number of pest eradication programmes are in action all over the infested areas in order to eradicate them. A study conducted by Maurice and Kumar in 2011 has found an alternative host plant for this beetle. They have recorded the oviposition as well as development of hadda beetle on a weed, Coccinia grandis and have concluded that this can weed can be used as a trap crop in order to save the economically important plants.