Attachment devices and the tarsal gland of the bug Coreus marginatus (Hemiptera: Coreidae)

Abstract

The present ultrastructural investigation using scanning and transmission electron microscopy as well as light and fluorescence microscopy describes in detail the attachment devices and tarsal gland of the bug Coreus marginatus (L.) (Hemiptera: Coreidae). In particular, the fine structure of pulvilli reveals a ventral surface rich with pore channels, consistent with fluid emission, and a folded dorsal surface, which could be useful to enhance the pulvillus contact area during attachment to the substrate. The detailed description of the tarsal gland cells, whose structure is coherent with an active secretory function, allows us to consider the tarsal gland as the plausible candidate for the adhesive fluid production. Scolopidia strictly adhering to the gland cells are also described. On the basis of the fine structure of the tarsal gland, we hypothesise a fluid emission mechanism based on changes of the hydraulic pressure inside the gland, due to the unguitractor tendon movements. This mechanism could provide the fluid release based on compression of the pad and capillary suction, as demonstrated in other insects. The data here reported can contribute to understanding of insect adhesive fluid production, emission and control of its transport.

Only Females Oviposit: Chemical Discrimination of Adult Stink Bug Sex by the Egg Parasitoid Trissolcus japonicus

“…In the epicuticular wax layer of stink bugs there are other components in addition to linear hydrocarbons, such as branched hydrocarbons or more polar components, the roles of which remain to be investigated in the context of the host searching behavior. Further, although the stink bug's cuticle appears to be the source of the contact kairomones that mediate the foraging response of egg parasitoids to walking traces, it cannot be excluded that cues may derive from adhesive substances produced by tarsal glands that facilitate the bugs' walking activity on different substrates, as recently observed in other Heteropteran species (Rebora et al, 2021). Although we tried to minimize the presence of defensive compounds, it cannot be excluded that a few chemicals observed in our analyses, such as dodecane and (E)-2-decenal were originated from methatoracic glands.…”

Morphology and ultrastructure of the epithelial femoral gland in cicadas (Hemiptera: Cicadidae)

“…The glandular cells of the epithelial femoral glands in cicadas join directly to the cuticle and lack associated duct cells, indicating they are glandular cells of class-1 (Noirot & Quennedey, 1974). Most exocrine glands that appear in the legs of insects, e.g., the exocrine glands in legs of bugs (Rebora et al, 2021) as well as the cicada gland here described, belong to class-1, with an exception of the basitarsal glands in Empididae and in Embioptera which are the only glands of class-3 (Young & Merritt, 2003). The epithelial cells have numerous basal invaginations and apical microvilli.…”

Comparative analysis of the ultrastructure and adhesive secretion pathways of different smooth attachment pads of the stick insect Medauroidea extradentata (Phasmatodea)

“…As transformed epidermal cells, the exocrine cells are responsible for the secretion of all cuticular layers apical to them, as well as the production of the adhesive secretion. These layers encompass the endocuticle layers 1 and 2, the adhesive secretion reservoir, the primary and branching rod layers, as well as the superficial layer [41,64]. These exocrine cells exhibit surface extensions into the hemolymph and adhesive secretion reservoir optimizing the substance absorption and discharge [31,[65][66][67].…”

“…The functional differentiation of the smooth attachment pads likely arises from differences in the ultrastructure and material composition of the pad types and is potentially supported by possible differences in the produced tarsal secretion. Despite extensive research on the attachment capabilities and the ultrastructure of the different attachment pads in various insect groups (for example, Coleoptera [5], Hemiptera [41], Diptera [42,43], Orthoptera [5,20,44], and Blattodea [45]), knowledge on the differences in the internal ultrastructure and fluid trans-portation between different types of smooth attachment pads located on the same tarsus is scarce, especially in Phasmatodea. Recent investigations of the ultrastructure and material properties of the smooth tarsal attachment pads of phasmids complement our information on the morphology of the droplets [38], biomechanics of their attachment performance [28,[46][47][48][49][50][51], and the complementarity of the two pad types [47,52,53].…”