The venom alkaloids from some African Monomorium species.

A comparative analysis of the venom alkaloids of 13 species of ants in the genus Monomorium collected in Africa was undertaken. Ants were collected in Kenya and South Africa. Most species produced 2,5-dialkylpyrrolidines and some of their analogous 1-pyrrolines. No alkaloids were detected in two species. M. robustior and M. macrops. Additionally, a novel 2-alkyl-1-pyrroline, whose structure was established by synthesis, was detected in M. notulum. This compound and others like it may serve as biosynthetic precursors for the formation of the 2,5-dialkylpyrrolidines found in many Myrmicine ant species.

Ammonia chemical ionization tandem mass spectrometry in structural determination of alkaloids. II. Tetraponerines from pseudomyrmecine ants.

Chemical ionization tandem mass spectrometry (CI-MS/MS) of alkaloids with ammonia reagent gas and collision-activated dissociation as well as EI-MS/MS were applied to the tetraponerine alkaloids in extracts from six pseudomyrmecine ants of the genus Tetraponera. The MS/MS techniques along with gas chromatography Fourier transform infrared (GC/FTIR) spectra allowed identification in two extracts of seven of the eight known tetraponerines. The EI-MS/MS fragmentations proved diagnostic for the ring system and the CI-MS/MS patterns for the C-8 or C-9 substitution, while the Bohlmann bands in FTIR spectra were diagnostic for the C-8 or C-9 configurations. An Indian ant (T. allaborans) had T-2, T-4 and T-8, while a Chinese ant (T. binghami) had T-5, T-6, T-7 and T-8. Four other ants, T. rufonigra (India), T. penzigi (Africa), T. clypeata (Africa) and T. sp. cf. emeryi (Africa), had no tetraponerines.

Novel dialkylpiperidines in the venom of the ant Monomorium delagoense.

New 2,6-dialkylpiperidines found in the venom of the ant Monomorium delagoense include cis- and trans-2,6-di(4-pentenyl)-piperidine [2], cis- and trans-2-(4-pentenyl)-6-pentylpiperidine [4], and cis- and trans-2-(6-heptenyl)-6-(4-pentenyl)-piperidine [7], whose structures were confirmed by synthesis. These compounds possess insecticidal and repellent properties.

Oviposition site selection in Cactoblastis cactorum (Lepidoptera): constraints and compromises.

Oviposition by Cactoblastis cactorum on Opuntia ficus-indica and O. aurantiaca was assessed from the positioning of egg sticks on plants in the field. The number of egg sticks laid on O. ficus-indica plants was affected by: (1) plant size; (2) moth emergence near the plant; (3) cladode condition; and (4) plant conspicuousness. These factors contributed towards the clumping of egg sticks on plants. There was no apparent oviposition preference for one of the two host plant species despite the fact that egg predation was higher and fecundity lower on O. aurantiaca. The selection of a site for oviposition on the host plants was influenced by: (1) cladode condition; (2) height above ground; and (3) shelter from wind during oviposition. Succulent cladodes were the favoured sites for oviposition. The evidence suggests that in C. cactorum, oviposition site selection is largely the net result of a compromise between oviposition behaviour selected for increasing the probability of juvenile survival and oviposition behaviour selected for increasing the probability of laying the full complement of eggs. In addition, environmental and physiological factors such as wind and wing-loading, are thought to place constraints on the range of sites available for oviposition.