Rice Weevils

Question 1

explain the morphology in the larva

Answer 1

• legless
• humpbacked
• whitish body
• small, tan head

Question 2

explain the legs of a rice weevil

Answer 2

• hydrophobic hairs on mesothoracic legs
• 6 legs, even spaced
• modified for rummaging through rice

Question 3

explain the rostrum of a rice weevil

Answer 3

• long, snout-like projection
• consisting of labrum, mandibles, maxillae, and labium
• used for making holes in plants/grains of rice
• females use it to make holes to place their eggs

Question 4

explain the patches on a rice weevil

Answer 4

four distinct oranges/yellow patches on elytra

Question 5

explain the thorax of a rice weevil

Answer 5

rounded pits scattered throughout the thorax

Question 6

explain the antennae of a rice weevil

Answer 6

two antennae extending laterally from the rostrum

Question 7

lifecycle - egg stage

Answer 7

• adult female drills a tiny hole into the grain with her rostrum and lays her eggs
• they lay on an average of 4 eggs per day
• takes 3 days to hatch

Question 8

lifecycle - larvae stage

Answer 8

• once hatched, the larvae feeds on the interior of the grain, consuming the endosperm
• the larval stage typically lasts for 20-30 days, during which the larva goes through several molts

Question 9

lifecycle - pupa sage

Answer 9

• the larvae pupate within the grain, forming a pupal chamber.
• the pupal stage lasts for around 5-7 days
• during this time, the insect undergoes metamorphosis, transforming into an adult weevil

Question 10

lifecycle - adult stage

Answer 10

the adult weevil emerges from the pupal chamber by chewing a hole in the grain

Question 11

explain the rice weevil’s reproduction

Answer 11

• mating usually occurs near food sources
• reproduce shortly after they emerge from the pupa stage
• enter reproductive diapause and they accumulate in the leaves duing winter

Question 12

role of male weevils in reproduction

Answer 12

• release pheromones (chemical signaling)
• visual display

Question 13

role of male weevils in reproduction - visual display

Answer 13

• moving their bodies
• using their antennae to tap on female antennae

Question 14

role of female weevils in reproduction

Answer 14

• laying their eggs on wheat seeds after mating
• close the seed off after laying her eggs to protect it
• each seed can hold up to a max of one egg
• the egg size is very small, allowing them to fit into the grain seed
• female do all of the parental care

Question 15

rice weevil habitats

Answer 15

• grain and fruit products
• maize and unpolished rice
• wheat
• humid, dark conditions

Question 16

rice weevil habitats - grain and fruit products

Answer 16

primarily found in grain products, but can move to fruit if needed

Question 17

rice weevil habitats - maize and unpolished rice

Answer 17

bigger adult rice weevils prefer maize and unpolished rice

Question 18

rice weevil habitats - wheat

Answer 18

smaller and younger rice weevils prefer wheat due to competition

Question 19

rice weevil habitats - humid, dark conditions

Answer 19

they prefer dark, enclosed spaces as well as warm, humid conditions

Question 20

rice weevil effect on farmland

Answer 20

• harmless to humans and don’t carry diseases
• but, they harm crop life and results in lower yield and grain quality
• this causes large financial loss to farmers and grain dealers

Question 21

how to control rice weevils on farmland

Answer 21

• they are largely affected by temperature
• controlling weevils with temperature ventilations can help preserve small amounts of grain

Question 22

rice weevils role in society

Answer 22

• crop loss
• economic impact
• food contamination
• ecological balance and decomposition

Question 23

rice weevil role in society - crop loss

Answer 23

infesting and damaging stored grains

Question 24

rice weevil role in society - economics impact

Answer 24

infestations lead to costly control measures and threaten agricultural industries

Question 25

rice weevil role in society - food contamination

Answer 25

infested grains become unstable for consumption

Question 26

rice weevil role in society - ecological balance and decomposition

Answer 26

• part of an ecological web as a food source
• their bodies contribute to nutrient cycling