Lasioderma serricorne
Lasioderma serricorne, more commonly referred to as the cigarette beetle, cigar beetle, paprika beetle or tobacco beetle, is a small beetle that shares a resemblance with the drugstore beetle and the common furniture beetle. The cigarette beetle, along with the drugstore and furniture beetles, all belong to the beetle family Ptinidae. The cigarette beetle can be distinguished from A. punctatum by its flatter thorax, whereas A. punctatum boasts a humped thorax. The cigarette beetle can be further differentiated from S. paniceum by its uniformly serrated antennae with unmodified apex, unlike the three-segmented apical "club" of S. paniceum. Additionally, L. serricorne has no evident grooves in its elytra, or hardened wing covers, compared to A. punctatum and S. paniceum which both have grooves.
In addition to cigarette beetle, other common names for L. serricorne include "tobacco bug", "tobacco borer", "tobacco weevil" and "cheroot beetle". Lastly, another common name for the species is "tow bug", after the species' tendency to feed on upholstery fillings such as tow, hemp, and flax.
The cigarette beetle measures between 2 and 3 mm in length, making the cigarette beetle relatively small, and it is dark brown in color. Despite its diminutive size, the cigarette beetle is a significant pest in tobacco related industries for which it gets its namesake. Beyond tobacco, the cigarette beetle will infest most dry goods, including cereals, dried fruits, herbs, flour, and certain animal products.
Geographically, L. serricorne'' is naturally found in pan-tropical regions, but they have been distributed all over the world through the dried goods trade. The distribution and success of reproduction of the species is heavily tied to their environment. Larvae of the cigarette beetle require temperatures between 15 °C and 40 °C in order to successfully hatch, with the most optimal range for fecundity being between 30 °C and 33 °C. While the cigarette beetle can be found globally, this temperature preference allows the species to thrive best in tropical zones where temperature conditions are most suitable to this ideal range.
The cigarette beetle also has strong flight capability, which contributes to its migration pattern. This ability to move efficiently between infested food sources to uninfested food sources greatly contributes to the species' success as a pest and its geographic range.
The primary food source for this species includes the stored commodities they infest, such as spices, seeds, rice, cereals, and most notably, dried tobacco leaves. The food source of the cigarette beetle significantly influences fecundity, developmental time, survival rates, and body weight. The lowest fecundity was reported with tobacco leaves as a food source, while flour produced the highest fecundity.
Geographic range
Lasioderma serricorne are 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 L. serricorne, specifically in terms of temperature. L. serricorne 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 for maximum fecundity, 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.Lasioderma 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
The common name of cigarette beetle may be misleading, as this species has a wide range of food resources. In fact, cigarette beetles have the most varied diet of storage insects, second only to T. castaneum.Lasioderma serricorne primarily feed 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 L. serricorne 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 L. serricorne.
Interestingly, L. serricorne is one of the only species known to inhabit and feed upon dry tobacco and its products. This is due to the fact that tobacco is nutritionally deficient and a prominent chemical in tobacco, nicotine, can cause nicotine toxicity in insects. Nicotine is an incredibly toxic substance to soft bodied insects and is one of the most effective botanical pesticides. It was previously thought that cigarette beetles were able to process nicotine into a less harmful chemical, cotinine. However, current research suggests that nicotine can pass unmetabolized through cigarette beetles without causing significant damage. Specifically, over 91% of digested nicotine can be recovered in the beetle's waste, or frass. It has been suggested that the microbes in L. serricornes gut have contributed to their ability to pass nicotine unmetabolized and harmlessly though their digestive systems.
While cured tobacco is the cigarette beetle's most abundant food source, they display preference amongst types of cured tobacco. It was found that cigarette beetles most prefer flue-cured type, and least preferred is Burley. It can be concluded that generally cigarette beetles have a preference for tobacco types with the highest sugar content and lowest nicotine percentage.
Adult
The most common food resource for adult cigarette beetles is cured tobacco leaves, particularly tobacco leaves stored in commodity warehouses and facilities. However, as stated earlier they will consume a wide variety of dried good product depending on where they hatched.Larvae
Newly emerged larvae will begin eating the substrate within which they were laid upon given that it is a suitable food resource. As for the amount of food larvae require, it takes about 0.012-0.15 g of food for a larva to grow into adulthood.When the substrate they are hatched on is not suitable for the cigarette beetle's diet, the larvae may eat the eggshell they hatched from, as well as other unhatched eggs. However, this is not sufficient to bring the larvae into adulthood, and the larvae will die if a suitable food source is not found.
Parental care
Oviposition
The number of eggs a female cigarette beetle will lay during oviposition varies greatly on the environment the female has to lay eggs on. Typically, a female will lay up to 100 eggs in an evening directly on their food source. Most eggs are laid by a female within 4 days of adult emergence, but females can lay eggs up to 12 days after emerging into adulthood. Most of the time, females will oviposit at or near the site where they themselves had developed. The females and males of the cigarette beetle species do not care for their offspring after oviposition is completed. The rate of oviposition in cigarette beetles is highest at the upper temperature limit for reproduction but decreased sharply at any temperature above this ideal range. The type of substrate the cigarette beetle lays eggs on can impact the number of eggs laid, where lying eggs on rice produced the smallest number of eggs and lying eggs on wheat produced the greatest number of eggs.Host learning and selection for egg laying
Cigarette beetles can be influenced on where to lay their eggs by smell. A study found that cigarette beetles produced significantly more eggs when given the opportunity to lay them on a food substrate as opposed to a non-food substrate. This effect can be found for a variety of food substrates, and although the success varies between types of food, all food substrates perform better than nonfood material.Odor
Part of L. serricornes ability to recognize the difference between food and non-food substrate and which would in turn make the best oviposition location is through odor. When a non-food substrate was soaked in the smell of tobacco and wheat, female cigarette beetles not only choose to oviposition there, but laid significantly more eggs than they did on the non-food odor substrate. This has implications for their success as a pest, as the more attractive a food environment is by odor, the more eggs they will lay. This knowledge has contributed to the production of odorous cigarette beetle repellant solution, which coats dried good in a non-food odor that deters them from lying eggs in packaged products.Life history
Life cycle
Egg
Lasioderma 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 and 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%.