Anatomical studies and behavioural observations indicate that representatives of the Orussidae use vibrational sounding to detect suitable oviposition sites. During host location, vibrations generated by tapping the tips of the antennae against the wood are picked up by the fore legs through the basitarsal spurs, transmitted along the basitarsi to thin-walled areas on the tibiae and through haemolymph to the subgenual organs, where they are transduced into nerve impulses. The apical antennomeres are distinctly shaped and have the cuticle thickened distally. The fore basitarsi have weakly sclerotised basitarsal lines proximally and membranous basitarsal spurs distally. The external wall of the fore tibiae have thin-walled areas distally on their posterior parts. Internally, large subgenual organs are situated opposite the thin-walled areas and each organ consists of 300-400 scolopidial units suspended between a lateral cuticular spine, a ventral sheet and a median ridge. The ovipositor is several times the length of the body of the wasp. When at rest, it extends all the way into the prothorax, where it is coiled before extending posteriorly to lie between the third valvulae distally. The ovipositor lies in a membranous ovipositor sac attached posteriorly to the proximal parts of the ovipositor apparatus and the posterior margin of sternum 7. In the ovipositor apparatus, the anterior parts of the second valvifers are displaced and expanded anterodorsally, inverting the first valvifers and the base of the ovipositor. When in use, the ovipositor is extended and retracted by median apodemes situated on the anterior margins of abdominal sterna 3-7. Longitudinal muscles between the apodemes allow the latter to grip the ovipositor in troughs between them. The ovipositor extends from the abdomen at the tip of sternum 7, and an internal trough on sternum 7 serves to guide the ovipositor into the wood. Despite the alterations observed in the ovipositor apparatus in the Orussidae, the musculature is almost complete and the mode of operation presumably not much different from that of other representatives of the Hymenoptera. The different ways parasitic wasps with very long ovipositors handle and accommodate these and the implications for the evolutionary history of Hymenoptera are discussed.

An electron microscopic survey of antenna cleaner morphology, mainly in non‐aculcate Hymenoptera, is presented. Modified, scale‐ or paddle‐shaped setae on the fore basitarsus were found to be widely distributed throughout the order, but were particularly well developed in the Xyeloidea. Megalodontoidea, Blasticotomidae, Siricoidca, Orussoidea, Cephoidea and Chalcidoidea. as well as in the aculeate family Formicidae. A comb of fine setae on the fore basitarsus was present in all Apocrita, with the exception of the Trigonalyoidea, Evaniidae, and some families of Chalcidoidea, but among the symphytan families was present only in the Orussidae. Members of the symphytan family, Anaxyelidae have a distinct line of discrete setae in the same position as the fine comb of the Orussidae and apocritans which we term a protocomb; members of the Cephidae also show an indication of a protocomb, in the form of a line of more widely spaced, erect setae, that could form part of the same transition series. Members of the Trigonalyoidea and of the Evaniidae have no comb of fine setae but do possess one or more rows of highly modified, plate‐like structures on the fore basitarsi.

X-ray microanalysis of the ovipositor and mandibles of various hymenopterous insects has revealed the presence in many species of up to 10% wt/wt of either zinc or manganese in the cuticle. These metals appear to be involved in cuticular hardening, so helping to reduce abrasive wear. Zinc is found in the ovipositors of most Siricidae, Stephanoidea, and Chalcidoidea. In Ichneumonoidea and Cynipoidea, the metal involved is manganese. Megalyroidea are unique in the Hymenoptera in having both zinc and manganese in their ovipositors, though in different locations. Except for Bethylidae, no metals were detected in the ovipositors or stings of species that penetrate soft substrates or do not make holes at all. The cutting edge of the mandibles of many insects that chew their way through hard substrates during egress from their pupation sites almost invariably contain high concentrations of zinc, and this is present in many that lack metals in their ovipositor. The phylogenetic and ecological implications of metal occurrence are discussed. 0 1998 The Linnean Society of London ADDITIONAL

Both external and internal gross morphology of multiporous plate sensilla were investigated throughout the Hymenoptera, with particular reference to nonaculeate families, using SEM. Several scenarios concerning the origin of multiporous plate sensilla are discussed. Shape, attachment, position, and reinforcing structures, were found to vary between the families, and the possible phylogenetic implications of these are discussed.

In the present study, mitochondrial DNA polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was used to assess the phylogenetic and phylogeographic relationships among 27 brown trout Salmo trutta populations from Turkey. The complete NADH 5/6 region and a second segment comprising the cytochrome b gene and D-loop of mtDNA amplified by PCR were digested with six and five restriction enzymes, respectively. A total of 27 haplotypes were observed and divided into three major phylogenetic assemblages, namely Danubian (DA), Adriatic (AD) and a newly proposed Tigris (TI) lineage. The timing of the net nucleotide divergence between the major lineages along with the geological history of Turkey suggested pre-Pleistocene isolation of the Turkish brown trout and provided evidence that Turkey could be considered as a centre of diversification for these lineages. The average haplotype diversity (0Á1397) and the nucleotide diversity (0Á000416) within populations were low in comparison to the observed interpopulation nucleotide diversity (0Á021266). PCR-RFLP analysis showed that most of the mtDNA sequence variation found in the Turkish brown trout populations was imputable to differences among lineages. On the other hand, there was also an obvious relationship between geographical distribution of the populations and their clustering. The present study showed that brown trout populations from Turkey are highly divergent and mainly have a unique genetic profile that could be used for conservation and management purposes.