Charlotte L. Fatland

Re-analysis of the cuticular methylalkanes of Solenopsis invicta and S. richteri

Gas chromatographic retention times and electron impact and chemical ionization mass spectrometry were used to identify two new series of dimethylalkanes in Solenopsis invicta Buen and Solenopsis richteri Forel. The first series consisted of internally branched dimethylalkanes with one methylene group between the branch points and were identified in an extract of cuticular lipids from S. invicta and S. richteri. The second new series consisted of 3,x-dimethylalkanes with odd carbon numbers, where x = 7, 9, or 11, and 4,x-dimethylalkanes with even numbers, where x = 8, 10, or 12. The mass spectrum published by Loket al. (1975), and which was tentatively identified as being that of 10,12-dimethyltricosane, is re-interpreted as being that of a mixture of 3,9- and 3,11-dimethyltricosanes. Internally branched monomethylalkanes, and 3- and 4-methylalkanes were found in the cuticular lipids of both species. 3,7,11-Trimethylalkanes were tentatively identified as being present in S. invicta. The n-alkanes and alkenes also were identified in S. richteri.

Insect hydrocarbons. 2. Mass spectra of dimethylalkanes and the effect of the number of methylene units between methyl groups on fragmentation.

Dimethylalkanes with one, three, four, five, and seven methylene units separating the methyl branches were synthesized and analyzed by mass spectrometry for comparison with the spectra of dimethylalkanes isolated from insect cuticular wax. Fragmentation reactions of these synthetic dimethylalkanes under electron impact verified assumptions based on the mass spectra of the natural products. Dimethylalkanes with 4 methylene units separating the two methyl branches had spectra that were unique to their structure.

Cuticular lipids of larvae and adults of the cigarette beetle, Lasioderma serricorne☆

There were qualitative and quantitative differences between the cuticular lipids extracted from the larval and adult stages of the cigarette beetle, Lasioderma serricorne. Triacylglycerols were the major components in the larval surface lipids, but the amount of cuticular hydrocarbon present in the larva increased fourteen-fold on a per insect basis to become the predominant lipid component in the adults. The composition of the free fatty acids was similar in both stages. n-Alkanes constituted 84% of the larval hydrocarbons but decreased to 17% in the adults. Conversely, branched-chain alkanes made up 83% of the adult hydrocarbon fraction. n-Tritriacontane (37% of the total hydrocarbon fraction) was the major larval hydrocarbon. GLC analysis of the adult hydrocarbons showed two major peaks, one a mixture of 11-, and 13-methylnonacosane and another a mixture of 3-methylnonacosane and 11,15-dimethylnonacosane. These two peaks account for 36% of the adult hydrocarbons. A series of internally branched dimethylalkanes in which the methyl groups were on adjacent carbons was identified in the cuticular lipids of the larvae of the cigarette beetle. This is the first time that such compounds have been found in insects. 11,12-Dimethyltritriacontane, 11,12- and 12,13-dimethyltetratriacontanes, 11,12- and 13,14-dimethylpentatriacontanes, and 11,12- and 13,14-dimethylheptatriacontanes were identified. 4-Methylhexacosane and 4-methyloctacosane were identified in the cuticular lipids of adults of L. serricorne. Such compounds have not previously been reported as specific components of cuticular hydrocarbons from insects.

Cuticular hydrocarbons of tsetse flies II:Glossina fuscipes fuscipes, G. palpalis palpalis, G. p. gambiensis, G. tachinoides, andG. brevipalpis

The alkanes (methylalkanes) were analyzed from both sexes of four members of thepalpalis group of tsetse flies,Glossina fuscipes fuscipes, G. palpalis gambiensis, G. palpalis palpalis, G. tachinoides plus onefusca group member, G. brevipalpis, to determine structures, abundances, and the presence of unique or specific methylalkanes. These insects are unique in that trimethylalkanes were major components except in femaleG. tachinoides and both sexes ofG. brevipalpis where 2-methylalkanes were the major components. The identification of novel long-chain tetramethylalkanes, including 11,15,19,23-tetramethylpentatriacontane, a minor component of femaleG. f. fuscipes, G. p. gambiensis, andG. p. palpalis, is reported here. Tetramethylalkanes were significant components of both sexes ofG. brevipalpis. The major tetramethylalkane in G.brevipalpis is 3,7,11,15-tetramethylhen-triacontane. The use of the methylalkanes as taxonomic indicators in tsetse is discussed.

Developmental changes in cuticular lipids of the black carpet beetle, Attagenus megatoma☆

Abstract The proportions of the major lipid classes extracted from the cuticle of the black carpet beetle, Attagenus megatoma, remained relatively constant throughout the larval period (about 260 days) but differed considerably from those in the surface lipids of the adult. Wax esters made up about 60% of the cuticular lipids in the larvae but only 12% in the adults. Hydrocarbons constituted 15–20% of the larval cuticular lipids but became the major lipid class (55%) in the adults. The composition of the hydrocarbon fraction of the adults differed qualitatively and quantitatively from that of the larvae. A homologous series of five alkenes was identified in the adults by using gas chromatography-mass spectrometry. One of these, 9-pentacosene, was the predominant component (31%) of the adult hydrocarbon fraction. Internally- and terminally-branched alkanes were also identified but they made up only about 2% of the total hydrocarbon fraction of the adults. The proportion of free fatty acids was similar in the larvae and the adults, but an increase in the amount of unsaturated fatty acids occurred in the adult stage. These total results indicate a shift from an abrasion-resistant hard wax layer in the larvae to a softer cuticular wax in the adults.

Hydrocarbons in the surface wax of eggs and adults of the Colorado potato beetle, Leptinotarsa decemlineata

The major components of the egg hydrocarbons were dimethylalkanes (40%) and trimethylalkanes (24%) in which the first methyl branch was on carbon 2. The major dimethylalkanes were an approximately 2:1 mixture of 2,10- and 2,6-dimethyloctacosanes in females and eggs. The major trimethylalkanes were a mixture of 2,10,16- and 2,10,18-trimethyloctacosanes. 2,x- and 2,x,y-methyl-branched alkanes with an odd-numbered carbon backbone were proposed to have an even number of carbon atoms between the first and second methyl branch points indicating that their biosynthesis started with a primer derived from leucine. 13,17,21,25-Tetramethylheptatriacontane was the only tetramethylalkane identified. Females and eggs had more hydrocarbons with a 2-methyl branch point than did the males. The eggs had the lowest amount of internally-branched dimethylalkanes but the largest amount of 2,x-dimethylalkanes in their surface hydrocarbons. Only trace amounts of n-alkanes and alkenes were detected in the surface hydrocarbons of adult males and females, larvae and eggs, of the Colorado potato beetle.

Novel wax esters and hydrocarbons in the cuticular surface lipids of the red harvester ant, Pogonomyrmex barbatus.

The cuticular surface lipids of the red harvester ant, Pogonomyrmex barbatus, were found to contain minor amounts of novel wax esters, in addition to the major components, hydrocarbons. The wax esters ranged in carbon number from C19 to C31 and consisted of esters of both odd- and even-numbered alcohols and acids. Each wax ester with a given carbon number eluted at several different retention times indicating possible methyl branching in either the fatty acid or alcohol moiety, or in both moieties. Each eluting peak of wax esters consisted of a mixture of wax esters of the same carbon number in which the fatty acid moiety ranged from C8 to C18, and the alcohol moiety ranged from C8 to C17. Some wax esters were largely found on the head indicating they may be of a glandular origin. The hydrocarbons consisted of: n-alkanes, C23 to C33; odd-numbered n-alkenes, C27 to C35; and the major components, methyl-branched alkanes, C26 to over C49. Notable components of the methyl-branched alkanes were 2-methyltriacontane, and the novel trimethylalkanes with a single methylene between the first and second branch points, 13,15,19-trimethylhentriacontane and 13,15,21-trimethyltritriacontane.

External lipids of adults of the giant whitefly, Aleurodicus dugesii

Abstract The external lipids of male and female adults of the giant whitefly, Aleurodicus dugesii , were found in three forms; as cuticular lipids, as waxy particles, and only on the females, as waxy filaments. Collectively, the external lipids consisted of long-chain aldehydes, long-chain alcohols and wax esters. Cuticular lipids consisted mainly of wax esters. The major wax esters were C44 (tetracosanyl icosanoate and docosanyl docosanoate) and C46 (mainly triacontanyl hexadecanoate and tetracosanyl docosanoate). Hydrocarbons, largely n -alkanes, were minor components of the cuticular surface lipids. Both sexes produced waxy particles soon after eclosion by breaking off extruding strands (or ribbons) from anterior wax plates on their abdomens; three pair on males and two pair on females. These particles coated the adults and their surroundings. The waxy particles produced by the anterior wax plates of the adults were a mixture of aldehydes and alcohols, predominantly C30. The wax esters were not part of the waxy particles despite being the major lipid class on the cuticular surface. In addition, the adult female has two pair of posterior abdominal wax plates which produce waxy filaments that are broken off during oviposition and form spiral trails on the leaf. These trails appear to function to camouflage the eggs which are laid horizontally in the waxy trail. The lipid obtained from the waxy filaments from the posterior abdominal wax plates of the female was largely wax esters. The predominant wax ester was C46 (mainly triacontanyl hexadecanoate).

Olefins as major components of epicuticular lipids of three Sitophilus weevils

1. 1. Cuticular hydrocarbons of adults of the rice weevil, Sitophilus oryzae (L.), maize weevil, S. zeamais Motschulsky and granary weevil, S. granarius (L.), were analyzed by gas chromatography and combined gas chromatography-mass spectrometry. n-Alkanes, methylbranched alkanes, n-alkenes, n-alkadienes and traces of n-alkatrienes were detected in each species. 2. 2. n-Alkanes composed 27.0, 26.6 and 43.3% of the hydrocarbons in S. oryzae, S. zeamais, and S. granarius, respectively. Even and odd chain components from C16 to C39 were detected in each species. n-Heptacosane, n-nonacosane, and n-hentriacontane were major components. 3. 3. Branched-chain alkanes were minor components (0.8–2.5%) of the total hydrocarbons in each species. Internally- and terminally-branched monomethylalkanes and internally-branched dimethylalkanes were identified. Internally branched dimethylalkanes with 11 (9,21-dimethyltritriacontane and 11,23-dimethylpentatriacontane) and 13 (11,25-dimethylheptatriacontane) methylenes between the branch points were identified in S. zeamais. 4. 4. n-Alkenes (C27:1 to C47:1) made up 18.5, 15.1 and 27.6% of the hydrocarbons of S. oryzae, S. zeamais, and S. granarius, respectively. n-Hentriacontene and n-tritriacontene were predominant components. Double bond positions were located primarily at 7–8 and 9–10. 5. 5. n-Alkadienes (C31:2 to C47:2) made up 53.7, 57.2 and 26.6% of the hydrocarbons of S. oryzae, S. zeamais and S. granarius, respectively. n-Tritriacontadiene, n-pentatriacontadiene and n-heptatriacontadiene were predominant components. Each GLC peak was an isomeric mixture. 6. 6. Hydrocarbon components of S. oryzae and S. zeamais were quantitatively and qualitatively very similar. However, significant differences were found between these two species and S. granarius. The use of cuticular hydrocarbons as chemotaxonomic markers in Coleoptera is briefly discussed.

Long-chain methylalkanes from haemolymph of larvae of Japanese beetles, Popillia japonica

Abstract Over 30 alkanes were found in haemolymph of larvae of the Japanese beetle, Popillia japonica . They consisted of several homologous series: the n -alkanes from 20 to 37 carbon atoms, a series of 2- and 3-methylalkanes from 25 to 31 carbon atoms, a series of internally-branched monomethylalkanes from 20 to 43 carbon atoms, and two series of dimethylalkanes consisting of from 23 to 32 and 41 to 47 carbon atoms, respectively. Only trace amounts of alkanes between 30 and 40 carbon atoms were present. The major n -alkane was tricosane (9%); the major monomethylalkane was 11-methyltricosane (20%); and the major dimethylalkane was 9,13-dimethyltricosane (40%). Also present were 2- and 3-methylalkanes, which eluted from OV-101 with the dimethylalkanes. About 16% of the alkanes were n-alkanes, 29% were internally branched monomethylalkanes, and 55% were dimethylalkanes plus 2- and 3-methylalkanes. Several very long-chain alkanes were found; on the basis of their equivalent chain length and mass spectra, we concluded that they represented a series of dimethylalkanes; 11,19-dimethyltritetracontane, 12,20-dimethyltetratetracontane, and 11,19- and 13,21-dimethyl-pentatetracontanes were identified.