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The geographic variation in the cuticular hydrocarbon pattern among 11 populations of Triatoma dimidiata Latreille (Hemiptera: Reduviidae: Triatominae) from different regions of Mexico and Guatemala, was studied using capillary gas chromatography. T. dimidiata populations were differentiated based on the relative amounts of 71 hydrocarbon components. Insect population classification was mostly in agreement with their geographical vicinity; Mexican populations from the Yucatan peninsula grouped together with those from northern Guatemala, insects from the Mexican Gulf coast states were closely related to those collected from northern Oaxaca, and to a lesser extent, to insects from Chiapas. Insects from southern Oaxaca were clustered together with those from southern Guatemala. All these populations were clearly separated from Guatemalan specimens collected in caves from Alta Verapaz.

The effect of alkane-growth induction of theentomopathogenic fungus Beauveria bassiana(Balsamo) Vuillemin (Deuteromycotina:Hyphomycetes), on the ability to kill the beanweevil Acanthoscelides obtectus Say(Coleoptera: Bruchidae), was tested. Adultinsects were sprayed with an 0.01% Tween 20aqueous suspension of 4 × 106 conidia/ml.The performance of fungi grown in complete agarmedium containing glucose as carbon source(FS0) was compared to that of alkane-grownfungi (FS1) with n-hexadecane as the onlycarbon source. Mortality increased (p< 0.05) from 22 ± 4.5% to 44 ±11.4% at day 7, and from 26 ± 5.5% to 60± 7.1% 14 days after treatment withFS0 or FS1 respectively. The insectepicuticular hydrocarbons were analysed bycapillary gas chromatography (CGC); majorcomponents were saturated hydrocarbons, 27 to29 carbons in length. A variety ofmethyl-branched isomers of C27 were theprevailing structures, and nC27 was the majorstraight chain component. Whole insecthydrocarbons were qualitatively identical tothose of the epicuticular surface. Oleic,linoleic and palmitic acids accounted foralmost 88% of the fungal fatty acids,irrespective of the carbon source used forgrowth; however, the unsaturated/saturatedratio diminished markedly from 4.32(FS0) to 2.47 (FS1). These resultsindicate that alkane supplementation of culturemedia might be a tool to improve the virulenceof some mycoinsecticides.

The geographic variation in the cuticular hydrocarbon pattern among 11 populations of Triatoma dimidiata Latreille (Hemiptera: Reduviidae: Triatominae) from different regions of Mexico and Guatemala, was studied using capillary gas chromatography. T. dimidiata populations were differentiated based on the relative amounts of 71 hydrocarbon components. Insect population classification was mostly in agreement with their geographical vicinity; Mexican populations from the Yucatan peninsula grouped together with those from northern Guatemala, insects from the Mexican Gulf coast states were closely related to those collected from northern Oaxaca, and to a lesser extent, to insects from Chiapas. Insects from southern Oaxaca were clustered together with those from southern Guatemala. All these populations were clearly separated from Guatemalan specimens collected in caves from Alta Verapaz.

The intraspecific variability of Triatoma dimidiata Latreille, a major vector of Chagas disease, was studied in four departments of Guatemala. Insects were collected from either domestic and sylvatic habitats, and their cuticular hydrocarbon pattern and head morphology were analyzed using ordination and classification techniques. A significant discrimination was obtained both with morphometric and hydrocarbon analyses. Insects from northern departments were easily differentiated from southern conspecifics. Distinctive hydrocarbon pattern and head shape were detected for insects collected from caves in the north central region of the country, posing concern about their taxonomic status.