Lasioderma serricorne

Lasioderma serricorne
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Family:	Ptinidae
Subfamily:	Xyletininae
Tribe:	Lasiodermini
Genus:	Lasioderma
Species:	L. serricorne
Binomial name
Lasioderma serricorne (Fabricius, 1792)
Synonyms
Lasioderma breve (Wollaston, 1861) Lasioderma castaneum (Melsheimer, 1845) Lasioderma flavescens (Dahlbom, 1837) Lasioderma fuscum (Rey, 1892) Lasioderma testaceum Duftschmidt, 1825 Lasioderma torquatum (Chevrolat, 1859) Pseudochina fuscum (Rey, 1892) Ptinus serricornis Fabricius, 1792 Ptinus testaceus (Duftschmidt, 1825) Xyletinus brevis (Wollaston, 1861) Xyletinus torquatum (Chevrolat, 1859)

Lasioderma serricorne, commonly known as the cigarette beetle, cigar beetle, or tobacco beetle, is an insect very similar in appearance to the drugstore beetle (Stegobium paniceum) and the common furniture beetle (Anobium punctatum). All three species belong to the family Ptinidae.

L. serricorne is around 2–3 mm long, and brown in colour. The beetles, which can fly, live 2–6 weeks and do not feed as adults. They can be distinguished from A. punctatum by the fact that A. punctatum has a thorax with a pronounced "humped" shape. S. paniceum and L. serricorne have thoraces which have a much less obtuse looking angle when viewed from the side compared to A. punctatum, and thus could be difficult to tell apart. However S. paniceum has a distinct three-segmented "club" at the end of each antenna whereas L. serricorne has uniformly serrated antennae of 11 segments. L. serricorne also has much weaker punctures on the surface of the wing covers (elytra) than the other two species.

As indicated by its common name, the cigarette beetle is a pest of tobacco, both in the refined cigarette packet presentation and also as stored in hogsheads and bales, but is also a minor pest of oilcake, oilseeds, cereals, dried fruit, sage, flour, and some animal products.

Geographic Range

The cigarette beetle is naturally found in pan-tropical areas but can be found anywhere where dried tobacco is stored . The species has been distributed throughout the world by transportation of infested dried goods Climate is vital to the growth and reproduction of the cigarette beetle, specifically in terms of temperature. Cigarette beetle larvae will not hatch below 15°C or above 40 °C. The longevity and fecundity of adult beetles are also impacted, both of which are significantly reduced at high temperatures. Climates in the 33°C to 37.5 °C range can significantly decrease the duration of the preoviposition period, while the oviposition period tends to lengthen at this temperature range. The ideal temperature range to maximize fecundity, or number of offspring, for cigarette beetles is 30 °C to 33 °C . Thus, the climate that is best suited to this species is the tropical zone, as a significant limitation to their geographic distribution is low temperature .

L. serricorne are strong fliers, which contributes to their migration patterns. Flying migrant L. serricorne beetles have a significant impact on the species’ ability to infest in different agricultural landscapes, which further contributes to the species’ wide geographic range .

Food Resources

Cigarette beetles primarily feed exclusively off stored commodities such as spices, seeds, rice, cereal, and most notably dried tobacco leaves. The fecundity, developmental time, egg to adult survival rate, and adult body weight of the cigarette beetle is heavily influenced by their food source. The food source that results in the highest fecundity is wheat flour, while the lowest fecundity is found when tobacco leaves are the primary food source. Additionally, larvae reared in wheat flour display the highest survival rates into adulthood. When infesting spices, cayenne pepper and paprika are the most favorable food sources to produce the highest body weights and longest life spans in cigarette beetles.

Life History

Life Cycle

Egg

L. serricorne eggs are white and opaque when they are first laid, but soon become yellow tinted after hatching. They are oblong in shape, and their length is generally 0.29 to 0.50 mm long with a diameter of 0.18-0.25 mm. An individual egg typically weighs between 8.0-9.0 μg.

The pre-oviposition period of L. serricorne ranges from 1 to 5 days. During oviposition, the female beetle will lay between 10 and 100 eggs in the evening or night directly on top of dried food material. The number of eggs laid can depend on the type of substrate they are laid upon. Crowding can cause the female beetle to deposit their mature eggs more quickly, but in general females will reduce the number of eggs they lay when faced with over-population . Eggs will usually hatch 6-8 days after they are laid, and at suitable temperatures egg viability can be up to 100% .

Larva

The cigarette beetle's larvae can be distinguished with difficulty from the grubs of the drugstore beetle, most easily by their longer hair and dark head capsule.

To hatch, the L. serricorne larva will chew through the chorion of the egg on the posterior side. The larva then lifts the chewed shell like a cap, which allows the larva to penetrate the opening . Freshly hatched larva are somewhat transparent, but gradually will assume a yellow-white color. When no other food is available, the larva occasionally will eat the rest of their eggshell as well as the shells of unhatched eggs surrounding them . When the larva emerges, it is typically active with the ability to move significant distances to search for food. This ability of the L. serricorne larva to move form infested to non-infested dried food sources contributes to the specie’s high rates of infestation. Their small size also gives them the ability to penetrate small openings in the seams of packaged commodities.

L. serricorne larva will molt twice and on the second molt will assume a scarabaeiform shape. After molting, larvae are typically less active, but they still are able to move considerable distances. At this stage, larvae tend to bury deep into commodities when they are in commodities that are packed loosely enough to do so. Fully grown larvae become immobile and stop feeding. At this stage, the larva will form a cocoon using food waste material and secretions from their midgut. Cocoons usually assume an ovoid shape, but this can vary. They typically measure 4.5 mm long and 3mm wide . In total, L. serricorne larva will typically undergo four growth periods before pupation, although this depends on the temperature they are reared in .

Pupation

Larva will remain in their cocoon for 2-4 days undergoing structural changes before emerging as a pupa. Pupae are a uniform white color that can be accompanied by a green tint when newly formed. The pupae will gradually take on a red-brown color that darkens as they age. Pupae are not active and have limited movement. The average length of a pupae is 3.5 mm with an average width of 1.7 mm . Pupae display sexual dimorphism, where male pupae have globular non-projecting genitalia while females have divergent genitalia .

Adult

Adult L. serricorne will stay in the pupal stage for 4-6 days before they emerge fully sexually matured and colored. The adult body is an elongated oval that is slightly convex. Their antennae contain 11 segments, some of which are distinctly triangular. Their matured color is a deep red-brown. There also exists a mutated black body form of the species .

Adult females will often weigh more than their male counterpart. The average length of an adult female is around 2.6 mm long, while the average width is 1.4 mm. For an adult male, their average length is 2.1 mm in length, and they have an average width of 1.2 mm. Adult L. serricorne have wings and are capable of flight. Adults typically live for 2-7 weeks but several factors influence their longevity such as mating status and larval food substrate .

Enemies

The most significant enemies of the cigarette beetle are the Anisopteromalus calandrae and Lariophagus distinguendus. Both parasitoid species will attack Cigarette beetles in the late larval and pupal stages .

Mating

Mate Searching Behavior

L. serricorne have the ability to mate successfully as soon as the emerge from the pupal cell, but typically mate 2-3 days after emerging. Mating typically takes place on top of the food substrate. The courtship of the adult beetles is facilitated by pheromonal and tactile stimulation provided by the female beetle. Male cigarette beetles will often attempt to mate with other males, as well, particularly when present near a pheromone source .

Pheromones

Female cigarette beetles produce a sex pheromone that incites a strong attraction in their male counterparts that excites them to mate. The pheromone is produced by a specialized gland in the female’s abdomen. The gland connects to a duct which allows for secretion from a pore above the female’s genitalia. The primary compound secreted by this gland is serricornin .

Responsiveness to serricornin increases with the age of unmated males, reaching maximum attractiveness in the fourth week of adult life .

After receiving a serricornin signal and experiencing an attraction to the female, a male will lower its head and vibrate their antennae, extending their forelegs, and quickly walk around. They then will mount the female.

Female/Male Interactions

During mating, the male and female beetles orient opposite each other so that only their abdominal ends touch each other. Both sexes of the species can mate multiple times and engage in repeated mating. Unlike other species, the amount of mating occurrences had no effect on the number of eggs that were lain .

Female cigarette beetles engage in polyandry. Mating with multiple males has shown to reduce female lifespan. This effect is heightened when one of their mates is an aggressive male. Aggressive males can cause a high cost of mating in Cigarette Beetle females due to increased male sexual harassment and damage from the male genitalia. The male genitalia can cause damage to the female’s reproductive tract with the spines it bears or by the toxic elements in their ejaculate .

Mutualism

With Microbes

Cigarette Beetles carry a symbiotic yeast, Symbiotaphrina kochii, that is transmitted to the next generation superficially on the eggs and carried internally in larvae and adults in the mycetome, a specialized organ that is linked to the gut. The yeast cells assist in the digestion of less nutritious foods, supply needed B-vitamins and sterols, and provide resistance to certain toxins.

The diversity of the cigarette beetle’s diet and ability to survive on foods of poor nutritional quality is due largely to their symbiotic relationship with the yeast species Symbiotaphrina kochii. The yeasts are transferred from parent to offspring when the egg passes through the oviduct. When the larvae hatch, they feed on the yeast which allows a population of yeast to grow in the mycetoma organ of the beetle’s gut. Here, the yeast produces a variety of B vitamins that are required to sustain life but may not be provided by the beetle’s diet .

Infestation

Main article: List of tobacco diseases

Tobacco and its related products can be infested by Lasioderma serricorne and Ephestia elutella (tobacco moth), which are the most widespread and damaging pests for the tobacco industry. Infestation can range from the tobacco cultivated in the fields to the leaves used for manufacturing cigars, cigarillos, cigarettes, etc.

During infestation, adults will make holes in food packaging to escape. Adults rarely feed on the infested material. Larvae causes the most significant damage to dried packaged goods .

The cigarette beetle is known for its economic impact on tobacco leaves. L. serricorne are estimated to be present in up to 1% of all warehoused tobacco product. Significant economic loss also occurs when the beetle infests individual products such as cigarettes .

Control in Commercial and Industrial settings

several views of Lasioderma serricorne specimen

Insect monitoring traps are available for L. serricorne, which contain specific pheromones to attract male beetles, and help detect and monitor infestations. Infested bulk tobacco in the form of bales or hogsheads can be fumigated using phosphine. Methyl bromide is labeled for tobacco, but is not approved for use by Corresta.

Dosage rates and treatment times with methyl bromide are 20 grams/m³ at 21 °C above and 32 grams/m³ for 48–72 hours at 7–20 °C. Methyl bromide is not recommended for cigar tobacco since it can produce off odours in the product. Methyl bromide is not acceptable to the tobacco industry.

With phosphine dosage rates are one gram of phosphine (equivalent to a 3-gram table) per m³ for 5 days at 12–15 °C and 4 days at 16–20 °C and 3 days above 20 °C. This dosage is not approved for phosphide resistant beetles. All tested beetles in the United States have shown resistance. Corresta Standards require a dosage that attains 600 ppm for 6 days at temperatures > 20°C.

For localised or household-level infestations the preferred control measure is to find the infested product, dispose of it, and treat around the area with a residual insecticide such as cypermethrin to kill off any remaining beetles.

Interactions with Humans and Livestock

Disease

L. serricorne has been known in rare cases to be associated with an infection called canthariasis, which is a human insectal disease caused by either the adult beetle or their larvae. Canthariasis infections transmitted to humans by the cigarette beetle has been reported in China and Malaysia. Transmission can occur by consuming food materials infested by L. serricorne larvae .

External links

• What is the Tobacco Beetle?
• Cornell Cooperative Extension Fact Sheet
• cigarette beetle on the UF / IFAS Featured Creatures Web site
• ZinRus High resolution photo