We report the molecular and stable isotopic (delta D and delta C-13) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21-33; maximum C-23-C-29) are found to be abundant in the insects (31-781 mu g/dry g), with a carbon preference index (CPI) of 5.1-31.5 and an average chain length (ACL) of 24.9-29.3. The isotopic compositions (mean +/- 1 sigma, n = 33) of the n-alkanes are -195 +/- 16 parts per thousand for hydrogen and -30.6 +/- 2.4 parts per thousand for carbon. The insect n-alkanes are depleted in D by approximately 30-40 parts per thousand compared with wax n-alkanes from C-3 (-155 +/- 25 parts per thousand) and C4 vascular plants (-167 +/- 13 parts per thousand), whereas their delta C-13 values fall between those of C-3 (-36.2 +/- 2.4 parts per thousand) and C4 plants (-20.3 +/- 2.4 parts per thousand). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift dD records of n-alkanes toward more negative values and potentially muddle the assumed original C-3/C-4 balance in the delta C-13 records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (dD(n-alkene) - delta Dn-alkane = -17 +/- 16 parts per thousand), but the delta C-13 values are almost identical to those of the n-alkanes (delta C-13(n-alkene) +/- delta C-13(n-alkane) = 0.1 +/- 0.2 parts per thousand). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes. (C) 2012 Elsevier Ltd. All rights reserved.