The most commonly found insect pests in stored grain

By Sanjeewa Dharmarathna - Understanding mill operation

Insects are first, most abundant, dominant & most successful form of life on earth, present since 250 million years ago. It includes 1-10 million different known species, classified under 32 different orders.

Insects are an integral part of any ecosystem, Aerobic, terrestrial and water, occur over 20,000 feet above the sea level and deep in the sea bottom. They show great diversity in habits, habitats and morphology, but share common traits with each other. 

Classification of Insects

Kingdom            : Animal Kingdom (Animalia)

Division             : Non-chordata (Invertebrata)

Phylum              : Arthropoda

Subphylum        : Mandibulata

Class                 : Insecta

Sub-class:

1. Apterygota (4 orders) (Premitive insects without wings).

2. Pterygota (Insects with wings)

 A. Exopterygota -wings develop externally in the nymphal stage (16 orders)

 B. Endopterygota –wings develop internally in the pupal stage (9 orders)

STORED PRODUCT INSECTS - CLASSIFICATION

Order: 1. Coleoptera - Insects with sheathy wings. Include all the Beetles. Most diverse and largest order consists of 125 different families (3, 00,000- 500, 000 species). One in every four species is a beetle.

Order: 2. Lepidoptera - Insects with scaly wings. Include Moths and Butterflies.

Lepidoptera: (1,10,000 species),

Hymenoptera: (1,10,000 species),

Diptera: (35,000 species)

Storage pests; 600 beetle species, 70 moth species, 355 mite species

INSECT MORPHOLOGY

Distinct body regions:

• Head
• Thorax
• Abdomen

Head:

6 segments fused to form head capsule, consists paired appendages Viz; mouthparts- maxill, mandibles, lacinia, eyes, antennae (Feeding and Sensory appendages).

Thorax:

Three segments categorized as Pro, Meso and Meta thorax, consist two pair of wings and three pairs of legs.

Abdomen:

8-10 segments, contains reproductive organs, ovipositor, endo and exocrine glands, digestive systems etc.

INSECT ANTENNAE

Role of antenna is primary, non-visual, sense organs. Males have more elaborate antennae than the females, to find the females. The greater the surface area more dilute scents they can detect.

ANATOMY OF ANTENNAE:

Scape: First segment of antenna which has attached to the insect body.

Pedicel: Second segment of the antenna, consists of mechano sensory organs like Johnston’s organ, helps in the recognition of different sources.

Flagellum: Remaining part of the antenna.

Some insect species lack antennae Viz., Protura.

Johnston's organ and intrinsic muscles are absent in Diplura and Collembola.

FUNCTIONS:

Insects communicate through smell or chemo-reception. Small sensory bodies (saccula/Sensilla) scattered over their body, primarily on their antennae, in some insects on legs. There are several types of chemo-receptor/sensory bodies;

1) Sensilla trichoidea: Hair-like structures commonly found on feet/antennae of insects, mainly helps in detection of mechanical stimulus, physical changes.

2) Sensilla basiconica and Sensilla styloconica: Peg-like or cone-like, thicker and more solid than trichoid sensilla, commonly found on antennae, and, also occur on maxillary palps of Lepidopteran larvae and the ovipositor of the Blowfly Phormia regina. 

3) Sensilla coeloconica or pit-peg organs these are always situated in a pit, commonly present on antennae and in Apis mellifera (the Honey Bee) they detect Carbon Dioxide. 

4) Sensilla placodea: Differ from other sensilla, consists of a flat plate of cuticle, they occur on the antennae of various Aphids and Apis mellifera (the Honey Bee).

5) Campaniform sensilla: Physical changes

INSECT EYES

Two types:

1.      Compound eyes

2.      Simple eyes or Ocelli

Compound eyes

Eyes can't close and move, can see well only to a distance of a few feet (about 90 cm). Compound eye composed of many facets/lenses called ommatidia, varies from 1-600 ommatidia per single eye, male Odonata have more than 28,000 per single eye.

Simple eye or Ocelli - single ommatidia.

The lens is formed by a transparent and colourless cuticle and it is usually biconvex. Beneath this is the crystalline cone which is comprised group of four cells called Semper cells functions as a secondary lens.

ANATOMY OF EYES

Divided into four basic parts:

1)     Supportive material that keeps all the parts together;

2)     Light gathering part (lens and auxiliary lens called a 'crystalline cone');

3)     Light receptor: converts the received light into electro chemical impulse.

4)     Nerves: carries electrical impulses to brain for analysis.

INSECT THORAX

Built up with series of upper concave and lower convex integument plates. Pro, meso and Meta thorax, Thorax shape and form vary according to the need of the insect. Thorax supports Heart and lungs, Flight muscles and respiratory openings/spiracles.

• Pro thorax- first pair of legs.
• Meso thorax- forewings and second pair of legs.
• Meta thorax- hind wings and third pair of leg.

INSECT ABDOMEN

Built up with series of upper concave integument plates known as 'tergites' and lower convex integumental plates known as 'sternites', both held together by a tough stretchable membrane called scutellum.

Consists of 8-11 segments, In Hymenoptera, and several other orders, the number of abdominal segments is reduced and in the Honey Bee only seven segments are visible. Supports digestive tract and reproductive organs,

Collembola' (Springtails) has only six segments. In the Hymenoptera there is a constriction where the 1st and 2nd abdominal segments meet, this is called the waste, and the remaining portion of the abdomen is called the gaster.

Adults do not have legs on the abdomen, in Protura' do have rudimentary leg-like appendages on the first three abdominal segments. Larval forms of Lepidoptera' and the 'Symphyta' (Sawflies) have pseudo or prolegs on their posterior abdominal segments. 

Metamorphosis

Metamorphosis: Change in form- transformation of an immature stage into a sexually mature stage of different in form, structure and habit.

Insects has four types of metamorphosis:

Ametabolous: No metamorphosis, newly hatched creature looks like an adult except in size. E.g. silverfish

Hemimetabolous: metamorphosis is incomplete, immature stages are nymphs which are aquatic. E.g. dragonflies.

Paurometabolous/gradual metamorphosis: The newly hatched creature resembles an adult, but lacks wing, immature stages are nymphs. E.g. cockroaches.

Complete Metamorphosis/ holo metabolous: distinct four developmental stages. E.g. beetles, housefly etc.

Ecdysis/Moulting: The shedding/casting off skin at intervals and grow into a new one of a larger size.

The stage between two moults is called as instar.

Hormonal control of metamorphosis:

Brain Hormone (BH): lipid in nature, secreted by the neurosecretory cells of the brain activates the somatogastric nervous system.

Prothoracicotropic Hormone (PTTH): secreted by the corpora cardiaca, stimulates the prothoracic glands.

Prothoracic Gland Hormone (PGH): Ecdysone, secreted by the paired, bilateral sheet of cells in the thorax induces morphogenesis. It is referred as moulting hormone.

Juvinile Hormone (JH): secreted by the corpora allata, regulates morphogenesis i.e. development of the larva into adult through pupal stage.

INSECT EGG

Insects are prolific in nature of oviposition. Size varies from 0.56 mm to 0.72 mm width and 0.62 mm to 0.74 height. Outer tough, rigid egg shell, below a wax layer , embroyonic layer, a wax layer, chorion, yolk and embroyo. Cap end consists of micropyles and pseuodomicropyles for the diffusion of oxygen to the embryo. Chorion protects the egg by mechanical injury and dessication.

 Excretory system

Uric acid: Main excretory product in insects.

Body fluids rushes into the Malphigian tubules by osmosis due to large concentrations of potassium ions inside the tubule. Body fluids rush back into the body cavity, nitrogenous wastes empty into the insect's hind gut. Water is reabsorbed and waste is expelled from the insect.

Waste products from the hemolymph diffuse into the Malpighian tubules, and are then converted to uric acid. The semi-solidified waste empties into the hind gut, and becomes part of the fecal pellet. The hind gut also plays a role in excretion. The insect rectum retains 90% of the water present in the fecal pellet, and reabsorbs it back into the body. This function allows insects to survive and thrive in even the most arid climates.

Respiratory system

Tracheal respiration - Spiracles/stigmata: Spiracles have fine hairs/bristles which act as filtering apparatus to keep out dirt and closing apparatus in the form of a valve to prevent undue loss of water and to regulate the flow of air in and out.

The tracheal system is an invagination of the cuticle. It is an extensive network of branching and anastomosing tubes. The wall is formed with chitinous layer which prevents the collapse of the trachea. The trachea gives rise to finer tubes called tracheoles.

The tracheal system resembles the circulatory system of vertebrate animals and serves the transport of oxygen and carbon dioxide.

Air sacs: The trachea dilate into air sacs of different sizes allow an increased supply of oxygen and afford a greater capacity for breathing even under stress conditions.

Reproductive System

Insects are prolific in nature due to their ability of large number of eggs produced per females and short life cycle.

Reproductive cycle:

Sexual maturation→ Locating the opposite sex → Mating → Pre oviposition period → Egg laying (oviposition) → Hatching of eggs → Development of immature stages of adulthood.

Female insects have two ovaries, connected with two lateral oviducts, one for each ovary, and join at the common oviduct. Each ovary comprises of numerous functional chambers called ovarioles. Egg production takes place in the ovarioles. Egg are then released into the oviduct.

Spermotheca: specialized bag like structure, stores sperms for the future fertilization.

Lays fertilized eggs with the help of ovipositor.

Ecology

Insects are Poikilotherms. Temperature: Above 40C and below 100C is lethal. Below 18C metabolic process retards. Optimum is 30C. RH: Optimum 60-70 %. Moisture content of grain: 12 % is optimum, below 9% oviposition retards, above 15 % leads to mould proliferation

CLASSIFICATION & IDENTIFICATION OF STORAGE PESTS

STORAGE BEETLE PESTS

Around 600 storage beetle insect species present on the earth.

Variety in forms, size, shapes, life history, food habits, wide range of adaptation and reproduction with various modes of locomotion viz. fly, swim, hop, crawl and just sit.

Survive and multiply under variety food processing/storage establishments’ viz. Silos, Shops, Farms, Houses, Bakeries etc.

They can live in various food products like cereal grains, Dried fruits, Milled and processed cereal products, oil seeds/oil cakes, spices, Sweets, Cheese, Meat, Dried fish etc. and can attack the product both in the field and stores. It can survive in the storage structure at below 2% of oxygen.

Temperature, RH and Moisture content of the stored produce plays a crucial role in breeding and development of storage insects.

Morphology of Beetles pests

Eyes: Compound, even ocelli are also present.

Mouthparts: wide range of feeding habits, well developed mandibles and maxilla adapted for chewing and biting activity, and cause marked damage to the materials. Mouth parts modified into their food habits. Beetles of the super family Curculionoidea mouth parts have a distinct snout that can bore into wood/food grain and suck sap.

The snout has mouth parts at its end and is used for penetration and feeding, and for boring a hole to lay the eggs, eg. Cotton boll weevil, the apple blossom weevil, the rice weevil. The Curculionidae are also called true weevils, or snout weevils.

Thorax: Meso and Meta thorax are attached to the abdomen, while Pro tharax is isolated between the head and trunk and covered by a dorsal plate called the pronotum.

Elytra: Forewing of an insect which is Hard and sheath like structure, covered with bristles/hairs and punctuations/striations.

Elytra helps in protection of internal soft organs, maintenance of balance during flight.

They are held against the abdomen at rest, meeting in a straight line down the middle of the back.

Hind wing: is membranous present beneath the elytra, helps in mechanism of flying.

Abdomen: nine to ten segments, some are not externally visible, each bearing a pair of spiracles.

Trogoderma granarium (Everts): Khapra beetle 

Order: Coleoptera

Family: Dermestidae

Serious pest of wheat, broken cereals, barley, etc. Cosmopolitan, favored by hot dry climates. It is reported absent from some countries like, Kenya, Uganda, Central and Southern Africa.

Adults – brownish black, covered with hairs/scales, 1.5 to 3.5 mm in length, Females bigger than males, Head-Retractive antennae- club. Short lived 9-12days.

70- 80 eggs per female, hatch in 6-20 days.

larva 5- 6.3 mm long, covered with numerous reddish brown tufts of setae, urogamphy, undergo diapause state, Larval life 4 weeks to 2 years depending upon temperature and food supply.

Pupal period 6-10 days.

LIFE CYCLE: 6 weeks to 4 years.

TEMP. : Max : 41oC, Min: 24oC, Optimum : 37oC.

RH: Max : 73 %, Min : 03 %, Optimum : 25 %.

Larva is destructive as an external feeder, adults do not feed.

Rhizopertha dominica (F.): Lesser grain borer

Order: Coleoptera

Family: Bostrychidae

Primary pest of cereals, split pulses, corn products and also attacks drugs, leather, cork, wood and paper boxes etc.

Body dark brown, 3-3.5mm in length and 1.4-1.6mm in width,  head deflexed, Elytra well defined with rows of punctures/dipressions.

Prothorax tuberculate and rasp shaped.

Antennae with large three segmented serrate club. strong flier, Long lived 4-6 months,

300-400 eggs / female, lay either single or in clusters, hatch in 6-14 days.

Larva 0.3-2.8mm long, active, whitish, head brown, anterior portion much swollen. Larval period 35-40 days, completed either within the grain or in the grain dust.

Pupa 3.9 mm long white, Pupal period 7-8 days.

LIFE CYCLE: 6- 8 weeks.

TEMP. : Max: 39C, Min: 18C, Optimum: 34C.

RH: Max: 70 %, Min: 25 %, Optimum: 55 %.

 Lasioderma serricorne (F.): Cigarette beetle

Order: Coleoptera

Family: Anobiidae

Serious pest of stored tobacco and its products. Infests spices, dates, peanuts, dried fish, drugs, herbarium medicinal plants, garlic bulbs, oil seeds, books, furniture etc.

Larvae are destructive as external feeders, adults do not feed, active fliers. Cosmopolitan.

Adults are brick red to reddish brown in colour, 2.5 to 3 mm long. Finely pubescent, with the head deflexed. Short lived 1-2 weeks

Elytra: no punctations and no striations.

 Antennae serrate with 11 segments without loose club.

100-120 eggs/ female, hatch in 6-10 days.

Larva 4.5 to 6 mm long, ‘hairy’, whitish and creamy wrinkled, grub like and curved. External feeder forms cocoons for pupation larval period 3-5 weeks. Pupates inside the cocoon with adhered food particles. Pupal period 6-10 days.

LIFE CYCLE: 25 - 35 days.

TEMP.: Max: 37oC, Min: 20oC, Optimum: 30oC.

RH: Max: 100 %, Min: 22 %, Optimum: 70 %.

Larvae are destructive as external feeders, adults do not feed, active fliers. Cosmopolitan.

 Stegobium paniceum (L.): Spice beetle; Drug store beetle

Order: Coleoptera

Family: Anobiidae

Serious pest of all spices, spice products, processed foods and herbal drugs. And can penetrate tin foils and sheet lead, good flier. Usually occur in tropical, sub-tropical and warm temperate regions.

Body oblong, 2.5 to 3.5 mm long, light brown to reddish brown coloured, with silky fine pubescence, deflexed head. Short lived 2-4 weeks.

Antennae 3-terminal segments enlarged to form loose club at the tip.

Elytra uniquely punctuate and plainly striated.

100-125 eggs /female, hatch in 8-24 days.

Larva is ‘hairy’, curved. External feeder, forms cocoons for pupation .Larval period 3-5 weeks.

Pupates inside the cocoon with food particles. Pupal period 6-10 days.

LIFE CYCLE: 6- 8 weeks.

TEMP.: Max: 37oC, Min: 20oC, Optimum: 30oC.

RH: Max: 100%, Min: 22 %, Optimum: 70%.

Both adults and larvae are destructive

Tribolium castaneum (Hbst.): Rust-red flour beetle

Order: Coleoptera

Family: Tenebrionidae

Secondary pest for grains but serious pests of broken grain and flour called ‘Bran bugs’. Infest baking powder, dried fruits and confectioneries.

Cannibalistic behavior seen, both adults and larvae eat on eggs and pupae.

Secrete defensive volatile secretions benzoquinones from thoracic and abdominal glands under stress or exposure to fumigants and CO2 and are suspected carcinogens.

Body flat, 3- 4 mm long, reddish brown. Strong flier. Long lived up to 4-10 months.

Antenna- 3 terminal segments enlarged abruptly.

 400-500 eggs / female, oblong, whitish, translucent and sticky, food particles, hatch in 5-6 days.

Larva flattened, active, whitish about 5- 6.3mm long. ‘Hairless’ with urogomphy. Larval period 4-10 weeks.

Pupate in produce without puparium. Abdominal segments with lateral combs and urogomphy. Pupal genital papillae2-segmented in females, 1-segmented in males. Pupal period 6-12 days.

LIFE CYCLE: 4-12 weeks.

TEMP.: Max: 40C, Min: 20C, Optimum: 32C.

RH: Max: 90 %, Min: 10 %, Optimum: 70 %.

Both adult and larvae are destructive Cosmopolitan and more common in tropics.

 Tribolium confusum (Duval.): Confused flour beetle

Order: Coleoptera

Family: Tenebrionidae

Secondary pest for grains but serious pests of broken grain and flour called ‘Bran bugs’. Infest baking powder, dried fruits and confectioneries.

Cannibalistic behaviour seen, both adults and larvae eat on eggs and pupae.

Secrete defensive volatile secretions benzoquinones from thoracic and abdominal glands under stress or exposure to fumigants and CO2 and are suspected carcinogens.

Body flat, 3- 4 mm long, reddish brown. Gena- its outward projection prominent, while not prominent in T.castaneum. Do not fly but T.castaneum are strong fliers. Long lived up to 4-10 months.

Antennal segments gradually enlarging towards apex, terminal segment longitudinally round, while in T.castaneum antenna is 3 terminal segments enlarged abruptly

400- 500 eggs/ female, oblong, whitish, translucent and sticky, hatch in 5- 6 days.

Larva dorsally convex, ventrally flattened, active, whitish about 5- 6.3mm long. ‘hairless’ with urogomphy. Larval period 4-10 weeks.

Pupa initially white, later yellowish brown, pupation takes place in produce without cocoon. Abdominal segments with lateral combs with urogomphy. Pupal period 6-12 days.

LIFE CYCLE: 4-12 weeks.

TEMP.: Max: 38C, Min: 20C, Optimum: 30C.

RH: Max: 90 %, Min: 10 %, Optimum: 70 %.

Both adult and larvae are destructive, Cosmopolitan and more common in tropics.

Both adult and larvae are destructive, Cosmopolitan and more common in tropics.

 Sitophilus oryzae (L.): Rice weevil    

Sitophilus zeamais (Motsch): Maize weevil

Order: Coleoptera

Family: Curculionidae

Serious primary pest of cereals, Infests rice, sorghum, wheat, maize, paddy. Both capable of infesting in the field, Native of India.

Body reddish-brown, 3- 3.5mm long, well defined rostrum, rostrum slender, thinner in females, while shorter, stouter in males. Long living- up to one year, average 4 - 5 months

Fore wing is modified into protective cover elytra and deeply striated with four light coloured spots. Hind wing membranous ,for fly.

Antennae elbowed with compact club. Round and dense punctures on prothorax.

Female bores a small hole into the grain and inserts the ovipositor to lay an egg, then plug it with mucilaginous secretions. After complete development, the adult bites its way out of the grain, leaving behind an emergence hole.

100 – 150 eggs/female, MC in grain favours oviposition (12-14 %). S.zeamais breeds well in 20 % moisture content, hatch in 3- 6 days.

Larva apodous, short, white, fleshy, 3- 3.5mm long with dark brown head, dorsally semicircular and ventrally flat. Larval period 25-34 days.

Pupate inside the grain, Pupal period 4-8 days.

LIFE CYCLE: 4- 6 weeks.

TEMP.: Max: 34C, Min: 17C, Optimum: 30C.

RH: Max: 100 %, Min: 45 %, Optimum: 70 %.

Both adult and larval stages are destructive. Cosmopolitan, internal feeder, both adult and larval stages are destructive. Cosmopolitan,

MOTH PESTS

CLASSIFICATION

Order: 2. Lepidoptera Insects with scaly wings. Include Moths and Butterflies.

Order: Lepidoptera :

1. Family: Gelechiidae   : Sitotroga cerealella

2. Family: Galleriidae   : Corcyra cephalonica

3. Family: Phycitidae    : Ephestia cautella, Plodia interpunctella.

Adults nondestructive, feeds on plant sap.

Larvae are destructive. Attacks almost all types of stored products.

Adult: variety of shapes, sizes, and colors. Body is long and slender. Females are larger than males.

Eyes: Compound eyes and some also have a pair of simple eyes.

Wings: Both the forewings and hind wings work together while the insect is in flight, wingspans of 0.39 to 0.75 inches (10 to 19 millimeters).

The wings are usually large than the body and are densely covered with tiny flat hair-like structures called scales.

Thousands of scales are arranged on the wings like overlapping shingles on a roof and give different color and patterns.

Mouth parts: A long coiled tube like tongue called the proboscis surrounded with a pair of maxillary palps, used for sucking up fluids.

In some proboscis is strong enough to pierce the skin of fruit. Some moths do not have a proboscis, and a few species have jaws.

 The antennae or sense organs, of moths are long and threadlike or feathery.

Abdomen: soft, ten-segmented is covered with scales and lacks any long projections on the tip.

Larval Body: Body is long, soft, and fleshy, vary in form sizes and colour. The head is distinct, hard, and has powerful jaws.

The body surface is wrinkled and smooth, covered with scales, fleshy bumps, spines, or tufts of hair. These coverings sometimes help to protect the caterpillars from potential predators.

Mouthparts: well developed mandibles and maxilla, adopted for chewing and biting habits,

Antennae: are small and not easily seen.

Webbing: Two silk glands are located inside the lower lip through which spin the silken webbing.

Legs: The six true legs are located on the thorax and has a series of paired prolegs. Each leg is five-segmented and usually tipped with a single claw.

Abdomen: 8-10 segmented, tip consists needlelike spines are sometimes hollow, attached to poison glands, and capable of delivering burning stings. The hairs of some species are especially irritating to people if they get into the eyes, nose, or mouth.

Pupa: The features of the adult are clearly visible in the pupal stage.

The legs and wings are tightly glued to the body along their entire lengths.

 The pupae of moths are usually brownish in colour and smooth.

They pupates in a silken cocoon.

Many moths pupate in the ground or under tree bark.

Sitotroga cerealella (Olivier): Paddy moth; Angoumois grain moth

Order: Lepidoptera

Family: Gelechiidae 

Attacks all cereal grains, wheat, maize, paddy, sorghum, barley etc. Infests both in field and granary. Infestation restricted to the periphery of stored grain. Serious pest in warm areas.

Wing expanse 12.7mm straw coloured or buff colored, fore wings trapezoidal with a fewer darker markings, hind wings abruptly narrowed at apical end, posterior margins heavily clothed with long setae, distinguished from other moths by its small size. Labial palps 3-segmented usually slender and pointed. Short lived 5-10 days.

120-400 eggs/ female. Fertilized eggs, initially pearly white later change to bright red or pink within 24 hours. Eggs are deeply fluted longitudinally, hatch in 5-7 days.

Larva strongly curved, thorax much stouter than the abdomen, white, later turns reddish in colour, matured larvae 12.7mm long. Prolegs indistinct, each with only two or 3 widely separated indistinct chrochets. 1st instar larva bores and closes the entrance hole with a spun silken web, and feeds upon soft endosperm of the kernel, forms cocoon inside the kernel just below the seed coat. Larval period 2-3 weeks.

Pupates within the silken cocoon inside the kernel, reddish brown colour. Pupal period 4 - 6 days.

LIFE CYCLE: 4- 6 weeks.

TEMP.: Max: 34oC, Min: 18oC, Optimum: 30oC.

RH: Max: 85 %, Min: 50 %, Optimum: 75 %.

Larval stage is destructive, adults do not feed. Cosmopolitan, serious pest in tropics.

 Corcyra cephalonica (Stainton): Rice moth

Order: Lepidoptera

Family: Galleriidae

Primary pest of rice, important pest of flour mill, forms silken webbing on material. It infests sorghum, millet, wheat, cocoa, oil seeds (pea nuts), copra, milled products, cocoa, chocolate, dried fruits, biscuits and some spices.

Wing expanse 19.05mm, fore wings uniformly coloured pale, grayish brown without spots but with the veins slightly darkened. Hind wings light gray. Labial palps straight, conspicuous in females, legs long, slender. Short lived 8-15 days.

150-200 eggs/ female, hatch in 3-5 days.

Creamy white in colour, matured larva is 15 mm long and 3 mm wide. 5 pairs "prolegs" on the abdominal segments. Larval head is pale brown in colour. Larval period is 18-22 days.

Pupa 7.5 to 9 mm long, with the short median, parallel, elevated, longitudinal lines and the nearly black anal segments bearing four processes (short spines) are characteristics.

LIFE CYCLE: 4- 5 weeks.

TEMP.: Max: 34C, Min: 18C, Optimum: 30C.

RH: Max: 90%, Min: 20%, Optimum: 75 %.

Larval stage is destructive, adults do not feed. Cosmopolitan, serious pest in tropics.

Ephestia cautella (Walker): Tropical warehouse moth; Fig moth

Order: Lepidoptera

Family: Phycitidae

Serious pest of dried fruits, figs, broken cereals, pulses and their products, biscuits, tamarind, oil seeds including groundnuts and palm kernels, cocoa, spices, animal feeding stuffs, flour materials, garlic, dry chillies , etc. Infestation is confined to surface layers of the stored commodity. Some strains of this species are capable of undergoing diapause stage under adverse conditions.

Wing expanse about 15.12 mm . Forewing, dull grayish with obscure markings with the basal darker band on the outer edges. The antennal basal joint is swollen in males. Short lived 8-12 days.

200-250 eggs/ female, laid on grain materials and on the gunny bags filled with grain, hatch in 3-6 days.

Larva 12-14mm long, have setae arising from pigmented spots on the cuticle, look brownish white in colour, larval head dark brown, mature larvae enter a wandering phase and completely obscure the bag surfaces with silken webbing before pupation.

Pupates in silken cocoons. Pupal period 8-12 days.

LIFE CYCLE: 4 - 5 weeks.

TEMP.: Max: 38oC, Min: 15oC, Optimum: 28oC.

RH: Max: 100 %, Min: 45 %, Optimum: 70 %.

Larval stage is destructive, adults do not feed. Cosmopolitan.

Plodia interpunctella (Hubner): The Indian meal moth

Order: Lepidoptera

Family: Phycitidae

A general feeder usually attacks cereals sometimes spices and dried fruits etc. similar to E.cautella. Larvae prefer to feed on the germ portion of seeds. Under unfavourable conditions undergo diapause condition.

Wing expanse 16-18mm. Forewing elongate with basal one third a pale yellowish buff colour, remainder reddish brown to copper colored. The hind wings uniformly silver grey with a long silky fringe of setae. Labial palps directed forward. The head with a strong cone of scales, absent in Ephestia species; males have antennal basal swelling. Nocturnal in habits, avoid strong light. Short lived 5-13 days.

300 – 350 eggs/ female, deposited in nutrient and laid singly or in clusters or in chains of up to 30 eggs, hatch in 2-15 days.

Mature larvae 10 to 13 mm long and 1.8 to 2.2 mm wide. Head moderately pale yellowish brown in colour, with usually 6 ocelli. Larva with pigmented spots on the cuticle. The outer portion reddish bronze with irregular dark bands. Spin a silken thread on which the larval droppings and other frass accumulate. Laraval life 26- 30 days.

Pupates in light brown silken cocoon. Pupal period 4-20 days.

LIFE CYCLE: 30 – 35 days.

TEMP.: Max: 36oC, Min: 20oC, Optimum: 29oC.

RH: Max: 90 %, Min: 40 %, Optimum: 75 %.

Larval stage is destructive, adults do not feed. Cosmopolitan.

Liposcelis bostrychophila : Psocids ; Book lice

Order: Psocoptera

Family: Liposcelidae

Psocids are not the major pests. They are essentially scavengers feeding on fragments of organic matter of plant or animal origin. Grow well in humid regions. Prefer to feed on mouldy food materials, old papers and museum specimens. Commonly seen on the wet patches on the walls of the warehouses. At high density they taint foodstuffs with waste products and can physically damage grains (rice, wheat etc.). They may elicit allergic reactions in sensitive persons.

Psocids of stored products are very small insects, about 1-1.5mm long, smaller than a pinhead, translucent bodied, winged or wingless Antennae are rather longer with 12-50 similar segments.

Mouth parts are of biting type. Females are brown coloured and males are light cream colourded.

LIFE SPAN: Live for about 6 months. The maximum recorded life span is 53 weeks feeding on skimmed milk powder.

EGG: Lay singly or in small batches. lay 3- 4 eggs per day and lay up to 200 eggs /female, hatch in 8-24 days and can reproduce parthenogenetically, Metamorphosis incomplete, Eggs hatch into nymphs.

The nymphs are almost colourless. Populations increase rapidly until the nymphs mature into adults.

LIFE CYCLE: 21 days under optimum conditions of Temp. & RH.

TEMP.: Max: 34oC, Min: 20oC, Optimum: 30oC.

RH: Max: 90%, Min: 22 %, Optimum: 70%.

Adults and Nymphs- Both are external feeders. Occurs in tropical, sub-tropical and warm temperate regions.