''Oryzaephilus mercator'', the merchant grain beetle, is a small, flattened
beetle
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
about 2.5mm in length.
It is a common, worldwide pest of
grain and grain products as well as
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
,
chocolate
Chocolate is a food made from roasted and ground cacao seed kernels that is available as a liquid, solid, or paste, either on its own or as a flavoring agent in other foods. Cacao has been consumed in some form since at least the Olmec civ ...
,
drugs, and
tobacco
Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...
.
The biology of ''O. mercator'' is nearly identical with ''
Oryzaephilus surinamensis'' (the sawtooth grain beetle).
It can be differentiated from ''O. surinamensis'' by its larger eyes and by the shape of the head, the area just behind the eyes of ''O. mercator'' is narrower than that of ''O. surinamensis'', which has a more triangular shaped head.
Unlike ''O. surinamensis'', adults are capable of flight.
Life cycle
Females produce from 500 to 1000 eggs in a year which are deposited within a food source.
The larvae are yellowish-white with a brown head and can reach a length of up to 3mm, larvae are active and move about through a food source as they feed.
Larvae
molt
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
two to four times
before pupating in a
cocoon-like structure made by joining together small grain kernels and pieces of kernels.
The total life cycle takes approximately 27–50 days.
As a stored grain pest
''Oryzaephilus mercator'' is one of the most commonly encountered pests in grain and grain products,
and will feed on any foodstuffs of vegetable origin.
Broken grain kernels are the principal food source but whole kernels may be penetrated and fed on.
This feeding results in the destruction of grain (
shrinkage). Further, the metabolism of a population of insects results in an increase of water absorption into the grain, which can cause mold growth.
Control
In commercial grain storage operations bins should be cleaned after emptying in order to prevent any insects from infesting new grain.
Fumigation can be used to eliminate infestations, and grain stored more than 6 months may need an application of pesticide to prevent infestation.
The fumigants used for control of insects in grain do not leave a residue when used properly
but are highly toxic and require a qualified pesticide applicator.
In the home, products susceptible to infection should be kept in sealed containers to exclude these beetles.
Freezing infested foodstuffs at -18 °C for six days will kill all stages of the ''O. mercator'' life cycle.
Infestations always center around a food source used for breeding and the identification and removal of all infested foodstuffs will eliminate the population
References
*
{{Authority control
Silvanidae
Beetles described in 1889
Agricultural pest insects