Home / Silvan Flat Bark Beetles (Silvanidae) / Saw Toothed Grain Beetle (Oryzaephilus surinamensis)

Saw Toothed Grain Beetle (Oryzaephilus surinamensis)

The saw-toothed grain beetle is a member of the family of silver bark beetles. They are a global pest to grains and similar products, alongcol3 chocolates, tobacco, and drugs as both a larva and an adult. Famed Swedish zoologist Carl Linnaeus first described this species in 1758.

Saw Toothed Grain Beetle

Scientific Classification

  • Family: Silvanidae
  • Genus: Oryzaephilus
  • Scientific name: Oryzaephilus surinamensis

Physical Description and Identification

Adult 

Size: 2.4–3 mm

Color:  They are dark brown.

Other Characteristic Features: The bodies of these beetles are of a slender build, with serrated ridges on the prothorax, which look like the teeth of a saw, giving it its name.

Oryzaephilus surinamensis

Larva

Larvae are yellowish-white with brown heads. They are 3 mm long. While most larvae feed on broken or damaged pieces of grain, larger ones can also bore through kernels. After going through 2-4 instars, the larvae begin to pupate.

Saw Toothed Grain Beetle Larvae
Saw Toothed Grain Beetle Larvae

Pupa

Pupation takes place incol3 a cocoon of broken grain for about a week, after which the adults emerge.

Egg

Eggs are white and small. They are laid on a food mass, with a female laying around 285 eggs in her lifetime. The time taken to hatch is temperature-dependent, with eggs hatching in 3-5 days at 27-29⁰C, but takes up to 10-15 days in colder temperatures.

Saw Toothed Grain Beetle Larvae

Quick Facts

Other namesMalt beetle
Lifespan6-10 months
DistributionWorldwide, but less common in colder regions like the northern part of the United States and Canada
HabitatAnywhere grains are present after harvest. This may be in storage, in transit, or retail stores
Seasons activeYear-round
HostsBirdseeds, cereals, chocolates, dried fruits, flour, pasta, pet foods, nuts, tobacco, and yeast
Diet of adultsSame as larvae
Saw Toothed Grain Beetle Damage

Identifying the Damage Caused by Them

The larvae cause the most damage as their feeding leads to shrinkage of the overall mass of stored products and the growth of mold due to water generated by the activities of the beetles. The ultimate consequence is that the grains and other food products become unfit for consumption, often rejected by customers or those purchasing them.

Did You Know

  • The beetle’s scientific name Oryzaephilus surinamensis means “rice-lover from Surinam”. Carl Linnaeus gave it this name upon acquiring specimens from Surinam.
  • They are nearly identical to the merchant grain beetle, with a few differences. Saw-toothed grain beetles have smaller eyes and a triangular head, against the bigger eyes and rectangular head of the latter. Merchant grain beetles can fly while the sawtoothed grain beetles cannot.
  • In the poem,  This Is The House That Jack Built, it is believed that in the line “the rat that ate the malt” is a reference to the malt beetle, as this species is alternately called.
Saw Toothed Grain Beetle Picture

Image Source: spencerpest.com, a4.pbase.com, extension.entm.purdue.edu, researchgate.net, bugs.com, bugguide.net

The saw-toothed grain beetle is a member of the family of silver bark beetles. They are a global pest to grains and similar products, alongcol3 chocolates, tobacco, and drugs as both a larva and an adult. Famed Swedish zoologist Carl Linnaeus first described this species in 1758.

Saw Toothed Grain Beetle

Physical Description and Identification

Adult 

Size: 2.4–3 mm

Color:  They are dark brown.

Other Characteristic Features: The bodies of these beetles are of a slender build, with serrated ridges on the prothorax, which look like the teeth of a saw, giving it its name.

Oryzaephilus surinamensis

Larva

Larvae are yellowish-white with brown heads. They are 3 mm long. While most larvae feed on broken or damaged pieces of grain, larger ones can also bore through kernels. After going through 2-4 instars, the larvae begin to pupate.

Saw Toothed Grain Beetle Larvae
Saw Toothed Grain Beetle Larvae

Pupa

Pupation takes place incol3 a cocoon of broken grain for about a week, after which the adults emerge.

Egg

Eggs are white and small. They are laid on a food mass, with a female laying around 285 eggs in her lifetime. The time taken to hatch is temperature-dependent, with eggs hatching in 3-5 days at 27-29⁰C, but takes up to 10-15 days in colder temperatures.

Saw Toothed Grain Beetle Larvae

Quick Facts

Other namesMalt beetle
Lifespan6-10 months
DistributionWorldwide, but less common in colder regions like the northern part of the United States and Canada
HabitatAnywhere grains are present after harvest. This may be in storage, in transit, or retail stores
Seasons activeYear-round
HostsBirdseeds, cereals, chocolates, dried fruits, flour, pasta, pet foods, nuts, tobacco, and yeast
Diet of adultsSame as larvae
Saw Toothed Grain Beetle Damage

Identifying the Damage Caused by Them

The larvae cause the most damage as their feeding leads to shrinkage of the overall mass of stored products and the growth of mold due to water generated by the activities of the beetles. The ultimate consequence is that the grains and other food products become unfit for consumption, often rejected by customers or those purchasing them.

Did You Know

  • The beetle’s scientific name Oryzaephilus surinamensis means “rice-lover from Surinam”. Carl Linnaeus gave it this name upon acquiring specimens from Surinam.
  • They are nearly identical to the merchant grain beetle, with a few differences. Saw-toothed grain beetles have smaller eyes and a triangular head, against the bigger eyes and rectangular head of the latter. Merchant grain beetles can fly while the sawtoothed grain beetles cannot.
  • In the poem,  This Is The House That Jack Built, it is believed that in the line “the rat that ate the malt” is a reference to the malt beetle, as this species is alternately called.
Saw Toothed Grain Beetle Picture

Image Source: spencerpest.com, a4.pbase.com, extension.entm.purdue.edu, researchgate.net, bugs.com, bugguide.net

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