ARS | Publication request: Stage-Specific Cuticular Lipids of Plodia Interpunctella (Lepidoptera: Pyralidae: Phycitinae): 2-Acyl-1,3-Cyclohexadiones from Larval Mandibular Glands Serve As Cuticular Lipids

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 27, 2004
Publication Date: June 30, 2004
Citation: Howard, R.W., Baker, J.E. 2004. Stage-specific cuticular lipids of plodia interpunctella (lepidoptera: pyralidae: phycitinae): 2-acyl-1,3-cyclohexadiones from larval mandibular glands serve as cuticular lipids. Comparative Biochemistry and Physiology (B) 138: 193-206.

Interpretive Summary: Insects are well known to protect themselves from water loss by having their body covered by chemicals known as cuticular lipids. In most insects these chemicals are hydrocarbons. We have found that the immature stages of a major stored grain pest, the Indian meal moth, does not use hydrocarbons as cuticular lipids, but rather uses novel types of chemicals not previously known as insect lipids. These chemicals are produced by specialized glands in the heads of the larvae. Although the chemicals were previously known to be used for other purposes by these insects, this is the first report of their use as cuticular lipids. The adult and egg stage of the Indian meal moth do not have these chemicals and instead use hydrocarbons as their cuticular lipids. The information obtained will be used to design selective control procedures that target the larval chemicals.

Technical Abstract: Cuticular lipid compositions of all life stages of the stored product moth Plodia interpunctella have been determined. Eggs and adults of P. interpunctella have cuticular lipid compositions consisting solely of hydrocarbons. The composition of the eggs and adult females are qualitatively nearly identical with ca. 86 hydrocarbons (11 n-alkanes, 39 monomethyl alkanes, 19 dimethyl alkanes, 11 trimethyl alkanes and 6 monoenes) except the females lack the 2-methyl alkanes found in the eggs. The adult males have a hydrocarbon composition qualitatively nearly identical to the females with the exception that they lack the monoenes. Larval and pupal cuticular lipids are dominated by a mixture of ca. 20 previously described (early 1980's) 2-acyl-1,3-cyclohexanediones (CHD's), with only minute amounts of n-alkanes on the larvae and pupae. The CHD's are produced and continuously secreted by the paired mandibular glands found in all larvae onto their silk webbing and food particles. Secretions from dissected mandibular glands have a qualitatively identical composition to larval cuticular extracts. The pupal stage (which does not have mandibular glands) is enclosed in a silk cocoon also coated with the CHD's laid down while the wandering stage larvae spin the cocoon. The CHD's have physical properties that closely mimic cuticular hydrocarbons, including melting point and boiling point range and hydrophobicity. This is the first report of an insect with a life stage that does not use conventional cuticular lipids for conservation of water.