Scientific Name: Trogoderma granarium Everts, 1899

Common Names: Khapra beetle (English)

Synonyms

Trogoderma khapra, Trogoderma affrum, Trogoderma quinquefasciata

Taxonomic Position

Phylum: Arthropoda

Class: Hexapoda (Insecta)

Order: Coleoptera 

Family: Dermestidae

Genus: Trogoderma

Host Range

Khapra beetles prefer grain, cereal products, particularly wheat, barley, oats, rye, maize, rice, pulses, flour, malt and noodles and oilseeds. They can also develop on animal matter such as dead mice, dried blood and dried insects.

Pest Destructive Stage

Primary pest

Larva - The beetle does not bore into host material but young larvae feed on damaged seed and older larvae on whole grains. Damage can be severe with weight losses of between 5-30% and in extreme cases 70%.

Damage Symptoms

The khapra beetle is principally a serious pest of stored products under hot dry conditions; complete destruction of grain and pulses may take place in a short time. In bag stores, the first signs of infestation are masses of hairy cast larval skins, which gradually push out from the crevices between sacks. Shed skins and faeces can also contaminate grain and cause allergic reactions.

Identification features

Egg

Eggs Initially milky-white, later pale-yellowish; typically cylindrical, 0.7 mm long and 0.25 mm broad; one end rounded, the other more pointed and bearing a number of spine-like projections, broader at the base and tapering distally.

Larva

• Total length of the first-instar larva is 1.6-1.8 mm, a little more than half of which consists of a long tail, made up of a number of hairs borne on the last abdominal segment.
• Body width is 0.25-0.3 mm, and colour uniformly yellowish-white, except for the head and body hairs which are brown.
• The head bears a short antenna of three segments. A characteristic feature of the larva is the presence of two kinds of body hairs: simple hairs, in which the shaft bears many small, stiff, upwardly directed processes; and barbed hairs, in which the shaft is constricted at regular intervals, and in which the apex consists of a barbed head.
• Simple hairs are scattered over the dorsal surface of the head and body segments. The tail consists of two groups of long simple hairs, borne on the 9th abdominal segment.
• Barbed hairs are found in pairs of tufts, borne on certain abdominal tergites. As the larva increases in size, the colour changes progressively from the pale yellowish-white of the first-instar larva to a golden or reddish-brown.
• A conspicuous feature of a khapra beetle infestation is masses of these hairy larvae and their cast skins.

Adult

• Males are 1.4-2.3 mm long, 0.75-1.1mm wide; adult females are 2.1-3.4 mm long, 1.7-1.9 mm wide.
• The head and pronotum are dark reddish-brown, elytra reddish-brown, usually with indistinct lighter reddish brown fasciae; centre of thorax and abdomen reddish-brown; legs yellowish-brown.
• The setae on the dorsal surface are of two types: evenly distributed, coarse, semi-erect, yellowish-brown ones; and, few scattered, dark reddish brown setae, colour of setae follows the colour of cuticles.
• The pronotum medially and laterally has indistinct patches of yellowish-white, ensiform (flattened) setae, and elytra with two or three indistinct band of yellowish-white, ensiform (flattened) setae.
• The median ocellus on the front is always distinct.
• Antennae are yellowish-brown, 9, 10 or 11 segmented, with 3-5 segmented club.

Life Cycle

• The khapra beetle produces between one and nine generations per year depending on factors such as the host species, temperature, light and moisture.
• High humidity slows down population increase.
• Adults live for 12-25 days and females lay between 50-100 eggs.
• The eggs, which are loosely scattered in host material, hatch in 3-14 days.
• Larval development usually takes 4-6 weeks during which time they moult 4-15 times.
• The pupal stage lasts 2-5 days and quiescent adult stage 1-2 days. The larval stage however, can last from a month to a year, if it enters diapause (dormant phase).