Stable isotopes and essential elements as biomarkers to determine feeding habits by Lasioderma serricorne

The cigarette beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae) is a pest of durable grain commodities, spices, and stored tobacco.  Since L. serricorne can potentially disperse between different landscapes and may feed on different hosts, understanding insects’ host use pattern may help to direct management efforts to specific commodity storages.  In this study, quantitative and qualitative differences of carbon and nitrogen isotopes and five inorganic elements (Mg, Mn, Fe, Cu and Zn) present in the insect body tissue were used to identify the dietary history of L. serricorne.  Adults reared on different hosts in the laboratory, including respective rearing media and insects collected from different field locations, were used in the study.  The δ¹³C values in the laboratory, reared L. serricorne, were similar to the values of respective rearing media with an enrichment of about 1‰ in the insect body.  The enrichment for δ¹⁵N value greatly increased from host to insect body and varied about +3.30 to +5.73‰ in beetles.  There was a distinct difference in δ¹³C values for insects raised on C₃-based or C₄-based hosts.  A majority of the field-collected beetles showed δ¹³C values similar to expectations for a C₃ plant (^-20 to ^-28%_o); however, a few beetles showed evidence for feeding on C₄ plants (<^-14%_o) or diet mixing between C₃ and C₄ plants.  Of the five inorganic elements evaluated, only Mn showed distinct variation in concentrations between the rearing media and insect body.  This study shows potential exists for delineating the food sources of L. serricorne, using carbon and nitrogen stable isotopes and elements like Mn.