The attachment ability of insects on surfaces are associated not only with the micro-and nanostructure of the adhering part of an attachment device, but also with the global scale kinematics responsible for contact formation and release. In the present study, the locomotory techniques of several representatives of insects from four different orders (Orthoptera, Heteroptera, Coleoptera, and Hymenoptera), possessing different types of attachment structures, are described. The study is based on video recordings of insects walking on a flat surface and on cylindrical rods of various thickness, imitating plant stems. Attachment devices of tarsi and pretarsi were visualized using Scanning Electron Microscopy. The results show a different manner in the use of adhesive structures on substrates with various curvatures. Insects bearing attachment pads on proximal tarsomeres usually touch flat and curved substrates using all tarsomeres, whereas insects with their attachment devices on the distal tarsomeres usually walk on flat surfaces using the distal tarsomeres of the overextended tarsus. On substrates, with diameters comparable to or larger than the tarsus length, insects walk above the stem by clasping the stem with the bent tarsi. On thin stems, insects clasp the stem between their tarsi and hang under the stem. Thus, on thin and thick rods, forces applied to attachment organs act in opposite directions. There are two methods of leg positioning for walking on a rough flat substrate. In the first case, the tarsus is straightened and the rough substrate is gripped between the claws and the proximal complex of attachment devices (tarsal euplantulae, fossulae spongiosa, and terminal spurs of tibiae). In the second case the tibia does not touch the substrate; the insect is supported only by distal tarsomeres. The tarsus is in an overextended condition. On rods, with diameters comparable to or larger than the tarsus length, insects walk by clasping the stem with the bent tarsi. This posture is characteristic for the majority of insects independent of the tarsal position they normally use while walking on a plane. If the rod's diameter is smaller than the tarsus length, walking insects usually clutch it between contralateral tarsi. Using such a posture they are supported by interlocking or by strong friction, generated by attachment devices of the proximal tarsomeres, and do not use attachment devices of the pretarsus. Contact with the substrate is reinforced due to the coordinated contralateral clutch using all supporting legs. It is concluded that the use of different types of attachment structures correlates with locomotory techniques.
The females of the spider wasps (Hymenoptera: Pompilidae) hunt spiders to provision their larvae. The genital structures of pompilid females are modified in a sting that is used for paralyzing the prey (spiders) and defense. The skeleto‐muscular structure of the sting apparatus of a typical representative of the family (Cryptocheilus versicolor) is examined. The shape of sclerites, their relative positions and articulations are described. Some morphological adaptations are described for the first time. The wide anal arc of the tergum IX provides a stiff support for the muscles that move the valvulae. The resilin structures in the areas of articulation support the work of muscles and in some cases replace them. The 1st valvulae form a venom duct along their entire length, which provides the delivery of the venom to a specific point. An unpaired flap in the venom duct provides a dose of venom in the sting. This mechanism probably enhances the speed and accuracy of the wasp's sting movements. Functions of muscles and interactions of the structures of the sting apparatus of C. versicolor are discussed.
The pretarsus in Chalcidoidea (Hymenoptera Parasitica): functional morphology and possible phylogenetic implications. -Zoologica Scripta , 35 , 607-626. The structure of the pretarsus of chalcid wasps (Hymenoptera: Chalcidoidea) was examined with light and scanning electron microscopy. The pretarsus of these wasps is characterized by a distal elastic widening of the planta that spreads over the arcus, by a pair of folding plates at the dorsal side of the arolium (the dorsal plates), and by the absence of auxiliary sclerites. The surface of the fully spread arolium of chalcids has a spongiform structure. The arcus of chalcids is an apodeme of the planta. The peculiarities of the inverting/everting biomechanics of the pretarsus of chalcids involve: 1) interactions between the elastic part of the planta, the dorsal plates and the manubrium, and 2) the functioning of the elastic part of the planta and the arcus together as a single unit. A single apical seta situated distally from the campaniform sensillae and proximal row of setae on the manubrium are regarded as putative synapomorphies of Chalcidoidea. A manubrium with a distinct proximal row of three setae characterizes almost all Eulophidae, Aphelinidae and Signiphoridae ('eulophid lineage') and Tetracampidae, whereas a row of two setae characterizes Mymaridae, Rotoitidae and Trichogrammatidae. Other studied families (Pteromalidae, Eurytomidae, Torymidae, Ormyridae, Eupelmidae, Encyrtidae, Perilampidae), which represent a 'pteromalid lineage', are characterized mostly by five setae in a proximal row, which could represent a synapomorphy for these groups, or a symplesiomorphy in Chalcidoidea, depending on rooting. However, the characters may be correlated with differences in body size that characterize the different lineages rather than being phylogenetically important. Other characters that may be phylogenetically informative are: 1) shape of the manubrium (spindle-like in Mymaridae, Rotoitidae, Trichogrammatidae and the 'eulophid lineage', but mostly bottle-like in representatives of the 'pteromalid lineage'), and 2) pubescence of the proximal part of the planta (sparse, thick setae in Rotoitidae, Trichogrammatidae and the 'eulophid lineage', but dense, slender setae in representatives of the 'pteromalid lineage').
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