They are blister beetles belong ing to the family Meloidae. They may be Mylabris pustulata. The adults feed on the flowers and youg fruits. They are major pests of cotton and other malvaceous plants, like okra. They are known as blister beetles because their secretions cause blisters on the skin. They are also known as cantharid beetles because earlier cantharidin oil was extracted from them.

According to Wikipedia, it is secreted by the male blister beetle and given to the female as a copulatory gift during mating. Afterwards, the female beetle covers her eggs with it as a defense against predators. The complete mechanism of the biosynthesis of cantharidin is currently unknown. Diluted solutions of cantharidin can be used as a medication to remove warts.

Some non-chemical means of control are:

• Dust stems with diatomaceous earth, then shake off excess
• Use a uv/fluorescent light with a kill bucket below containing soapy/oily water
• Cover the plants with a fine mesh (e.g. www.enviromesh.co.uk)
• Use spinosad as a spray – environmentally friendly, and relatively safe to the operator
• Use nematodes, if affordable.