Test of Practical on Grain Weevil and Rhinoceros Beetle.

Weevils and rhinoceros beetles have short but pointed and strong mouthparts (rostrum) for boring a hole into grain.

They have chewing mouth parts.

The Life cycle of the weevil and rhinoceros beetle is a complete metamorphosis, and a larva is called a grub.

• Test of Practical on Millipede and Centipede (Myriapoda).

• Test Practical on Prawn/Crayfish, Crab, and Woodlouse.

• Test of Practical on Stem Anatomy of Dicotyledoneae and Monocotyledoneae Plants.

The habitat of the weevil is grains and plants that it can affect are: maize, sorghum, rice, groundnut, cowpea, cassava flour, oat, and wheat.

The rhinoceros beetle can affect plants such as oil palm, coconut, banana, yams, and beans.

They belong to a group of organisms named beetles because of;

• They possess horny fore wings called elytra.
• They have protruding biting/chewing mouthparts called a rostrum

Biological classification

Phylum Arthropoda

Reasons:

• Presence of a chitinous exoskeleton
• Metameric segmentation
• Presence of jointed appendages attached to each segment.
• Bilaterally symmetrical
• Triploblastic coelomate
• Open circulation (haemocilic)
• Undergo moulting.

Class Insecta

Reasons:

• Presence of three body divisions
• Presence of a pair of antennae
• Presence of three pairs of thoracic legs
• Presence of a pair of compound eyes
• Presence of spiracles for breathing

Order Coleoptera

Reason:

• Horny fore wings called elytra. (They are modified hind wing cases that protect the hind wings.)
• They have protruding biting/chewing mouthparts.
• Presence of rostrum.

Observable Adaptive Features of the Weevil

• Wings for flying
• Rostrum for boring into grains
• Chitinous exoskeleton for protection against mechanical injury and prevention of excessive evaporation of water.
• Antennae for sensitivity
• Can feign death when disturbed.
• Small size enables them to hide among grains to be transported.
• Colour to blend with its environment.

Economic importance of weevils

• It destroys grains/causes post-harvest loss
• It contaminates stored grain
• It reduces the economic value of grains
• It reduces the food value of grains
• It is expensive to control weevils

Economic importance of beetles

• Adults and larvae attack the palm, chew flowers and fruits to prevent fruiting.
• Causes pollination.
• Larvae are a source of food.

Effects of the rhinoceros beetle on crop production

• Chewing mouthparts chew flowers.
• Pollination of flowers.

Control of weevils.

• Treat stored grain with insecticides
• Irradiation of stored grains
• Use resistant varieties of crops
• Cultural practices such as crop rotation
• Isolate infected grains
• Aeration of stored grain circulates air, thereby reducing the temperature, which is not conducive to breeding
• Dry grains because high moisture is good for insect growth
• Proper sanitation, such as sanitising bags of old seeds to prevent eggs or larvae. A dirty environment enhances the breeding of insects
• Regular monitoring of stored grains

Disadvantages of control methods

• The use of insecticides can cause air pollution
• Can reduce food value
• Can cause food poisoning

Observable Features for Feeding in weevil

• Rostrum for boring a hole into grains
• Chewing mouth parts for chewing food

Adaptations to escape danger in weevil

• Feigning death (behavioural adaptation)
• Chitinous exoskeleton (morphological adaptation)
• Elytra to protect the hind wings (morphological adaptation)
• Hind membranous wings for flying (morphological adaptation)

Similarities between the grain weevil and the grasshopper.

Both have;

• a pair of antennae
• three pairs of legs
• three body divisions into head, thorax, and abdomen
• a chitinous exoskeleton
• a metameric segmented body
• jointed appendages
• compound eyes
• Forewings of a grasshopper protect the hind wing and also provide camouflage
• Forewings of weevils to protect hind wings
• Both hind wings for flying.

Differences between the grain weevil and the grasshopper.

• Test of Practical on Millipede and Centipede (Myriapoda).

• Test Practical on Prawn/Crayfish, Crab, and Woodlouse.

• Test of Practical on Stem Anatomy of Dicotyledoneae and Monocotyledoneae Plants.

Similarities between the grain weevil and the soldier termite

Both have;

• a pair of antennae
• three pairs of legs
• three body divisions into head, thorax, and abdomen
• a chitinous exoskeleton
• a metameric segmented body
• jointed appendages.

Differences between the grain weevil and the soldier termite

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