Cuticular lipids protect insects from desiccation and may determine resistance to fungal pathogens. Nonetheless, the trade-off between these lipid functions is still poorly understood. The migratory locust Locusta migratoria and the Italian locust Calliptamus italicus have dissimilar hygrothermal preferences: L. migratoria inhabits areas near water bodies with a reed bed, and C. italicus exploits a wide range of habitats and prefers steppes and semideserts with the predominance of sagebrushes. This paper presents significant differences between these species’ nymphs in epicuticular lipid composition (according to gas chromatography with mass spectrometry) and in susceptibility to Metarhizium robertsii and Beauveria bassiana. The main differences in lipid composition are shifts to longer chain and branched hydrocarbons (di- and trimethylalkanes) in C. italicus compared to L. migratoria. C. italicus also has a slightly higher n-alkane content. Fatty acids showed low concentrations in the extracts, and L. migratoria has a wider range of fatty acids than C. italicus does. Susceptibility to M. robertsii and the number of conidia adhering to the cuticle proved to be significantly higher in C. italicus, although conidia germination percentages on epicuticular extracts did not differ between the species. We propose that the hydrocarbon composition of C. italicus may be an adaptation to a wide range of habitats including arid ones but may make the C. italicus cuticle more hospitable for fungi.

The article provides a preliminary screening of Asian locust larvae aged 2-3 years for the virulence of 25 isolates isolated from insects belonging to different systematic groups of fungi Beauveria bassiana. Five of the 25 strains showed high biological activity against larvae, (BCo1-14, BSc1-15, BSc2-15, BTr1-16, BPit-16) reaching a mortality rate of 90-100% 21 days after inoculation. The strains that have the best effect on the level and rate of mortality of the host organism are - BCo1-14, BSc1-15, BSc2-15, BTr1-16, BPit-16. The greatest biological activity was observed in the BSc1-15 strain, as the mortality rate of test organisms was only 100% within 15 days of exposure. The lowest activity was shown by the BCi4-14 strain in the range of 35.0-62.5%. At the same time, the mortality rate of Asian locust larvae in the control variant (without treatment) for 21 days was 15.0±2.88%. Thus, the proportion of highly toxic forms (80-100% lethality) in the total number of studied strains was not more than 44%, and the proportion of mildly toxic forms (less than 80% activity) was 56%.