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Concept: Prothorax


Nanomaterials are being used in medicine, manufacturing and consumer products, but their effects on organisms and the environment are not well understood because of the difficulty in detecting them. Here dual-energy X-ray K-edge subtraction was used to track two-dimensional yttrium oxide nanoparticles (which can be found in such household objects as color televisions) in adult mealworms (Tenebrio molitor). The insects ingested nanoparticle-infused feed for different time periods, up to 24 h, and the nanoparticles could then be identified at several locations in the insects' head, thorax and abdomen, mostly within the digestive tract. In time, all particles were excreted.

Concepts: Biology, Insect, Digestive system, Abdomen, Thorax, Insect wing, Prothorax, Yttrium(III) oxide


The thorax morphology, especially the muscles and the tracheal system of three flightless species of Cryptorhynchinae is examined by digital 3D reconstructions based on synchrotron X-ray microtomography and compared to other Curculionidae. Wings, metanepisternites, and muscles functional in flight are fully reduced in the species examined: Kyklioacalles roboris (Curtis), Trigonopterus scharfi Riedel and Trigonopterus vandekampi Riedel. All three share the same set of thoracic muscles, but differences exist in the shape and size of muscles. Both Trigonopterus species examined have a conspicuous fan-shaped branch of Musculus mesosterni primus contracting pro- and mesothorax, interpreted as an adaption to their thanatosis defense strategy. Trigonopterus vandekampi furthermore shows a marked increase in the size of two metacoxal muscles, which may be functional in this species´ thanatosis blocking mechanisms. The metathoracic spiracle of all Trigonopterus species is located at the side of the metaventrite externally and not in the subelytral space as in other beetles. It is hypothesized that this translocation was triggered by the need to improve oxygen supply during thanatosis, when both the mesothoracic spiracle and the subelytral cavity are tightly sealed from the outside.

Concepts: Insect, Mimicry, Beetle, Thorax, Boll weevil, Curculionidae, Prothorax, Weevil


Movements of the elytra and axillary sclerites were video recorded in tethered flying beetles and in manipulated mounts. Mesothoracic axillary plates are homologues of those in the metathorax. Two anterior axillaries (Ax1, Ax2) fuse together; they are hinged to the third axillary plate (Ax3). In turn, Ax3 is hinged with the elytron. During takeoff, a beetle abducts and highly elevates its elytra (1), then droops the elytra in a flatly spread position (2); closing is adduction in a horizontal plane (3). These steps have been simulated: (1) by pressing down the anterior horn; (2) occurred spontaneously after release of pressing; (3) the elytron closed flatly either by manual turn of the elytron or by manual elevation of the prothorax. Anterior axillaries rotated forward and down during (1), returned during (2) and remained immobile during closing. Ax3 is folded between the closed elytron and Ax1+Ax2; it unfolds during opening. Two hinges of Ax3 form a Z-configuration and provide a linked drive for complicated rotation of the elytron. Opening was impaired in vivo if tergal leg protractor and depressor were disabled, closing did not suffer. Closing was prevented by excision in the hind edge of the pronotum, not harmful for opening. Role of direct and indirect muscles in transient elytral movements is discussed.

Concepts: Insect, Beetle, Rotation, Entomology, Adephaga, Dytiscidae, Elytron, Prothorax