Infochemical-mediated preference behavior of the parasitoid Microctonus hyperodae when searching for its adult weevil hosts

Infochemicals are the most important cues used by parasitoids for host location. The attractiveness of infochemicals in a tritrophic context is expected to be determined by the degree of specialization of the parasitoid and its host(s). Microctonus hyperodae Loan (Hymenoptera: Braconidae) is an oligophagous parasitoid that attacks adult Curculionidae of the Brachycerinae subfamily, especially Listronotus bonariensis Kuschel, on Gramineae. In 1996, a new host–parasitoid association between the carrot weevil Listronotus oregonensis LeConte and M. hyperodae was created in the laboratory. In this study, the infochemicals used by M. hyperodae when searching for its adult weevil hosts were determined using a Y‐shaped olfactometer. Three curculionid species (L. oregonensis, Listronotus sparsus Say, and Neydus flavicaudis Boheman) and one bruchid species [Callosobruchus maculatus (Fabricius)], and their feces, were tested. It was expected that hosts phylogenetically and ecologically close to L. bonariensis would be more attractive than species less related but in fact, M. hyperodae responded only to L. oregonensis and its feces. When feces and host insects were tested separately, M. hyperodae responded to the odors emitted by L. oregonensis adults but not to their feces, suggesting that most of the kairomones came from the host itself. Host plants were also tested, but M. hyperodae responded neither to Lolium multiflorum Lamark (Gramineae) nor to Daucus carota L. (Umbelliferae) leaves.     

Biology of Galaxiella munda McDowall (Teleostei: Galaxüdae), including a comparison of the reproductive strategies of this and three other local species

The reproductive biology, growth and diet of Galaxiella munda McDowall in a south-western Australian river are described. Monthly trends in gonadosomatic indices, stages in ovarian development and the size and maturity of oocytes show that spawning extended from July to October and peaked in late August to early September. Histology of ovaries indicated that G. munda produced clutches of eggs which it released at intervals. Data on length-frequencies, otoliths and gonads demonstrate that G. munda typically died in the few months after spawning. By age I, the females and males of G. munda had reached 47 mm (≡ 0.54 g) and 43 mm (≡ 0.42 g), respectively. The respective von Bertalanffy growth curve parameters for L., K and to were 48.6 mm, 3.702 and -0.0014 for females and 44.3 mm, 4.217 and -0.0012 for males. Galaxiella munda fed predominantly on terrestrial fauna on the water surface, cladocerans and copepods in the water column, and dipteran larvae in the benthos. Comparisons are made between the above aspects of the biology of G. munda and those recorded for three other locally endemic species ( Galaxias occidentalis Ogilby, Bostockia porosa Castelnau and Edelia vittata Castelnau) and wherever possible with other Galaxiella species. Such comparisons have emphasized the relationship between size and age at first maturity and spawning mode.     

Sex differences in search and gathering skills

The hunter–gatherer theory of sex differences states that female cognition has evolutionarily adapted to gathering and male cognition to hunting. Existing studies corroborate that men excel in hunting-related skills, but there is only indirect support for women excelling in gathering tasks. This study tested if women would outperform men in laboratory-based computer tests of search and gathering skills. In Experiment 1, men found target objects faster and made fewer mistakes than women in a classic visual search study. In Experiment 2, participants gathered items (fruits or letters presented on screen), and again, men performed significantly better. In Experiment 3, participants' incidental learning of object locations in a search experiment was studied, but no statistically significant sex differences were observed. These findings found the opposite of what was expected based on the hypothesis that female cognition has adapted to gathering. Alternative interpretations of the role of object location memory, female gathering roles and the division of labor between the sexes are discussed.     

Role of chemical cues and natal rearing effect on host recognition by the parasitic wasp Melittobia digitata

Parasitoids are expected to have the ability to find, recognize, and perhaps to discern potential hosts that can best support the development of their progeny. Melittobia Westwood (Hymenoptera: Eulophidae) are gregarious ectoparasitoids, which primarily attack mud daubers (Hymenoptera: Sphecidae). How Melittobia females locate their host is not well known, but the process may involve host‐related chemical signals. In this study, we investigated the roles of host chemical cues and natal rearing effect in host recognition by Mel. digitata Dahms. In an olfactometer that contained prepupae of Trypoxylon politum Say (Hymenoptera: Sphecidae), Megachile rotundata (Fabricius) (Hymenoptera: Megachilidae), puparia of Neobellieria bullata (Parker) (Diptera: Sarcophagidae), empty or intact host cocoons, or nest mud, Mel. digitata females spent significantly more time in air fields that contained T. politum (prepupae + cocoon) and Meg. rotundata (prepupae + cocoon) than in N. bullata and control fields. Nest mud and natal host had no attraction for parasitoid host choice. Most first and last choices of Mel. digitata females in the olfactometer were not consistent, suggesting an initial random dispersion, although they responded positively towards hosts in cocoons.