Sitophilus zeamais

Motschulsky, 1855

Maize Weevil, Greater Rice Weevil

Sitophilus zeamais, commonly known as the maize or greater , is a major pest of stored cereal products and standing in tropical and subtropical regions worldwide. The is closely related to Sitophilus oryzae (rice weevil) and can be distinguished by morphological features and preferences. It infests maize, wheat, rice, sorghum, oats, barley, rye, buckwheat, peas, and cottonseed. Research indicates this species has a longer and higher than S. oryzae, with females living approximately 109 days and producing around 203 on average. The species exhibits olfactory responses to cereal volatiles, which mediate host-finding .

Sitophilus zeamais by (c) Miroslav Deml, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Sitophilus zeamais: /ˌsaɪ.toʊˈfaɪ.ləs ˌziː.əˈmeɪs/

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Identification

Sitophilus zeamais is morphologically similar to Sitophilus oryzae () and (). It can be distinguished from S. granarius by the presence of (S. granarius is flightless). Separation from S. oryzae requires examination of the and elytral punctation patterns. S. zeamais typically has more widely spaced punctures on the pronotum and is generally associated with maize and warmer climates, whereas S. oryzae is more common on rice. The two can hybridize, complicating identification in areas where both occur.

Images

Habitat

Stored grain products and standing in tropical and subtropical regions. Found in warehouses, grain elevators, and farm facilities. Attacks both harvested stored grains and pre-harvest standing crops in the field.

Distribution

Tropical areas worldwide; present in the United States. Distribution extends across regions with warm climates suitable for year-round . Records include the Azores (Corvo, Faial, Flores, Graciosa, Pico).

Diet

Feeds on stored cereal grains including maize, wheat, rice, sorghum, oats, barley, rye, buckwheat; also attacks peas and cottonseed. Both and feed internally within grain kernels.

Host Associations

Zea mays - primary maize/corn
Oryza sativa - rice
Triticum spp. - wheat
Sorghum bicolor - sorghum
Avena sativa - oats
Hordeum vulgare - barley
Secale cereale - rye
Fagopyrum esculentum - buckwheat
Pisum sativum - peas
Gossypium spp. - cottonseed

Life Cycle

. , , , and stages all develop within the grain kernel. Average duration approximately 49 days under laboratory conditions (longer than S. oryzae at 35 days). mortality approximately 77%. Sex ratio approximately 0.77 (male-biased).

Behavior

exhibit electroantennographic responses to volatile compounds emitted by cereal grains, using olfactory cues for location. Demonstrates behavioral attraction or repellence to specific cereal volatiles. Adults are capable of , unlike the flightless S. granarius.

Ecological Role

Serious pest of stored products; reduces grain weight and quality through feeding damage. Internal feeding by destroys individual kernels. Can facilitate fungal of stored grains.

Human Relevance

Major economic pest of stored cereals worldwide. Causes significant post-harvest losses in developing countries. Subject of extensive research on and alternative control methods including . Frequently used as a model organism in stored-product research.

Similar Taxa

Sitophilus oryzaeExtremely similar ; historically confused with S. zeamais. S. oryzae has shorter (35 days vs. 49 days), shorter lifespan, and lower (152 vs. 203 ). S. oryzae more commonly associated with rice; S. zeamais with maize. The two can hybridize.
Sitophilus granariusSimilar size and appearance, but S. granarius is flightless ( , no ), has more closely spaced pronotal punctures, and is adapted to cooler temperate climates. S. zeamais has functional wings and is tropical/subtropical.