Egg clutch patterning in Lestes virens (Odonata, Lestidae) with evolutionary emphasis on endophytic oviposition in lestid dragonflies.

Egg deposition within plants is one of the most widely distributed and ancient behaviors in Odonata. The resulting clutch consists of eggs placed in peculiar pattern that can be a characteristic for certain groups of Odonata. Despite their importance for paleontological and evolutionary research, data on egg-clutch positioning are missing or insufficient for most species. Here, patterning of egg clutches in Lestes virens was measured and described in detail for the first time. The female usually produces a linear row of single eggs directed at an angle rightward or leftward to the longitudinal axis of plant substrate. Less often eggs are arranged in egg-sets consisting of up to 4 eggs. Apparently, the female insect follows the rigid behavior stereotypes during oviposition and is unable to easily switch to the alternate stereotypical behavior of single egg deposition or production of multiegg sets. Based on a literature review and original data, egg clutch patterning of European Lestidae is overlaid on preexisting phylogenies. The resulting evolutionary scenario of egg-clutch patterning can be considered in the framework of egg-laying behavior in Lestidae.

The exoskeleton of the female genitalic region in Petrobiellus takunagae (Insecta: Archaeognatha): insect-wide terminology, homologies, and functional interpretations.

The exoskeleton of the female genitalic region (abdominal venters 7-9) in Petrobiellus takunagae (Machilidae-Petrobiellinae) is studied using light microscopy and SEM. Sclerites are distinguished from membrane by the degree of cuticular flexibility. However, the microsculpture of the cuticle is shown to be useful in characterising the heterogeneity of the cuticle and in detecting weak sclerotisations. The morphology of Petrobiellus is compared with that in Trigoniophthalmus alternatus (Machilidae-Machilinae) described previously. While venter 7 is similar, venters 8 and 9 show many differences in the presence/absence or fusion/separation of particular sclerites. This suggests female genitalic morphology to be a valuable character system for phylogenetic and taxonomic work in Archaeognatha. Comparison with other insect orders is aimed at detecting homologous structures and conditions. Important points are: (1) Petrobiellus has a sclerotised genital lobe posteriorly on venter 7, similar to Zygentoma and Dictyoptera; it bears the gonopore. (2) Petrobiellus has a posterior sclerite on venter 9 that is very similar to a sclerite of Odonata. (3) The morphology of the coxal lobes of venter 9 (gonoplacs) suggests their function as a sheath of the ovipositor. From female genitalic morphology we deduce the process of oviposition, describing an external egg transportation tract.

The gonangulum: a reassessment of its morphology, homology, and phylogenetic significance.

The gonangulum is a sclerite in the female genitalic region of insects. Its presence or full development has long been considered an apomorphy supporting Zygentoma + Pterygota. Recent studies of female genitalia in several insect orders (K.-D. Klass and co-workers) revealed many new data on the gonangulum and homologous sclerotisations (laterocoxa LC9). Herein the gonangulum area is described (including articulations, muscle attachments, sulci) and compared among Archaeognatha, Zygentoma, Odonata, Dermaptera, Dictyoptera, and Notoptera. A wider perspective is provided to the topic by addressing some novel issues: identification of LC9 sclerotisations in non-insect taxa and in insects that secondarily lack an ovipositor; occurrence of homonomous sclerotisations in other abdominal segments of both sexes; morphological interpretation of LC9; and the role of paedomorphosis in LC9 evolution. As a result, there is currently no support for any insect lineage from this character system. For gonangulum-related characters both a significant intra-ordinal variation and frequent homoplasy are demonstrated using various Odonata, Dermaptera, and Dictyoptera as examples. Divergent fates of LC9 in simplified genitalia are shown using a dermapteran and an odonatan. We view all this as a showcase of how a renewed and more detailed examination of a character system can dramatically change the phylogenetic evidence drawn from it.

Skeletomuscular development of genital segments in the dragonfly Anax imperator (Odonata, Aeshnidae) during metamorphosis and its implications for the evolutionary morphology of the insect ovipositor.

The skeleton-muscular organisation of abdominal segments 7-9 in female Anax imperator L. (Anisoptera, Aeshnidae) was examined in the stages of ultimate larva, teneral imago, and mature imago, with special emphasis on the transformation of the muscle arrangement. The absence of certain muscles in the genital segments compared to the 7th pre-genital segment was noted on all studied stages. Reductions of certain muscles in adults compared to those in larvae are reported. Some of ovipositor's muscles appear already in larvae. Attachment sites of larval muscles are retained in freshly emerged females concurrently with integument transformations. This situation allows for precise determination of the borders of newly differentiated genital sclerites and, therefore, of the possible origin of certain ovipositor elements in odonates. All changes in the segmental sets of studied abdominal muscles during metamorphosis are tabulated, and displacements of muscles are documented and illustrated. Schematic figures illustrating homologies between the parts of larval and imaginal abdominal sclerites are provided. The origins of the components of the endophytic ovipositor in Odonata as well as their implications for the evolutionary morphology of the insect ovipositor are discussed.