Jumping mechanisms and performance in beetles. II. Weevils (Coleoptera: Curculionidae: Rhamphini)

A new species of Karekizo Morimoto, 1962 (Coleoptera: Curculionidae: Molytinae) from the Alishan Mountains of Taiwan and a first record of Karekizo impressicollis outside Japan

Karekizo Morimoto, 1962 represents a rarely collected, mountain-dwelling genus which has hitherto been known only from one species, K. impressicollis Morimoto, 1962, in Japan. Here, a second species, Karekizo depressus sp. n., is described based on a single specimen collected from Fen-Chi-Hu, Chiayi Hsien, Taiwan. The type species, K. impressicollis, is reported for the first time outside of Japan, from South Korea (Jeju Island, Mt. Hallasan). X-ray microtomography is used to non-destructively compare the sub-scale cuticular structure (e.g., density of punctures, presence of tubercles or carinae) of the two species. A photographic key to the species is also presented.

Jumping mechanism in the marsh beetles (Coleoptera: Scirtidae)

The jumping mechanism with supporting morphology and kinematics is described in the marsh beetle Scirtes hemisphaericus (Coleoptera: Scirtidae). In marsh beetles, the jump is performed by the hind legs by the rapid extension of the hind tibia. The kinematic parameters of the jump are: 139–1536 m s⁻² (acceleration), 0.4–1.9 m s⁻¹ (velocity), 2.7–8.4 ms (time to take-off), 0.2–5.4 × 10^–6 J (kinetic energy) and 14–156 (g-force). The power output of a jumping leg during the jumping movement is 3.5 × 10³ to 9.6 × 10³ W kg⁻¹. A resilin-bearing elastic extensor ligament is considered to be the structure that accumulates the elastic strain energy. The functional model of the jumping involving an active latching mechanism is proposed. The latching mechanism is represented by the conical projection of the tibial flexor sclerite inserted into the corresponding socket of the tibial base. Unlocking is triggered by the contraction of flexor muscle pulling the tibial flexor sclerite backwards which in turn comes out of the socket. According to the kinematic parameters, the time of full extension of the hind tibia, and the value of the jumping leg power output, this jumping mechanism is supposed to be latch-mediated spring actuation using the contribution of elastically stored strain energy.

Functional Morphology of the Thorax of the Click Beetle Campsosternus auratus (Coleoptera, Elateridae), with an Emphasis on Its Jumping Mechanism

Simple Summary

Click beetles are well-known for the specialized thoracic structure, which they can click to thrust themselves into the air and to right themselves. Several aspects of their jumping mechanism were still not entirely clear prior to this study. We utilized traditional dissection, 3D virtual dissection, and high-speed filming techniques to investigate the functional morphology of their thorax. Our results show several new insights into their extraordinary clicking and jumping mechanisms.

Abstract

We investigated and described the thoracic structures, jumping mechanism, and promesothoracic interlocking mechanism of the click beetle Campsosternus auratus (Drury) (Elateridae: Dendrometrinae). Two experiments were conducted to reveal the critical muscles and sclerites involved in the jumping mechanism. They showed that M2 and M4 are essential clicking-related muscles. The prosternal process, the prosternal rest of the mesoventrite, the mesoventral cavity, the base of the elytra, and the posterodorsal evagination of the pronotum are critical clicking-related sclerites. The destruction of any of these muscles and sclerites resulted in the loss of normal clicking and jumping ability. The mesonotum was identified as a highly specialized saddle-shaped biological spring that can store elastic energy and release it abruptly. During the jumping process of C. auratus, M2 contracts to establish and latch the clicking system, and M4 contracts to generate energy. The specialized thoracic biological springs (e.g., the prosternum and mesonotum) and elastic cuticles store and abruptly release the colossal energy, which explosively raises the beetle body in a few milliseconds. The specialized trigger muscle for the release of the clicking was not found; our study supports the theory that the triggering of the clicking is due to the building-up of tension (i.e., elastic energy) in the system.

Mechanical Design and Performance Analysis of a Weevil-Inspired Jumping Mechanism

Jumping mechanisms constitute an important means of resolution in applications such as crossing uneven terrain and space exploration. However, the traditional design mainly uses engineering design thinking, but seldom studies the structural characteristics of organisms themselves and lacks biomimetic research basis, which leads to the difference between jumping mechanism and biological structure and its jumping ability. On the other hand, it lacks in-depth study on biological jumping mechanism from the view of engineering. Weevil has excellent jumping performance, and its key jumper structure is specially designed by biologist. To investigate the motion mechanism and working mechanism of the jumping mechanisms, this paper takes the weevil as the bionic object, and designs a weevil-inspired jumping mechanism. A miniature prototype is designed to reproduce weevil’s jumping mechanism with its working principle and anatomical structure to verify how weevil’s jumping mechanisms work, and turns out to perform well at jumping height. This paper is presented the anatomical structure and working principle of the weevil jumping mechanism, followed by explanation and analysis of its kinematics and dynamics, then performing virtual prototype simulations to compare different design schemes, with results guiding the parameter optimization and subjecting a prototype machine into a height test. In comparisons among existing jumping mechanisms whose jumping method is bio-inspired, the present design, which weighs 44.7 g and can jump to a maximum height of 2 m. The present research establishes a biologically inspired working principle and provides a new practical archetype in biologically inspired studies.

Mechanical and optical properties of the femoral chordotonal organ in beetles (Coleoptera)

The femoral chordotonal organ (FCO) in beetles differs from that in orthopterids in the origin of its apodeme: it originates directly from the tibia in the latter, but amidst the tendon of the extensor muscle in the former. In many beetles, the apodeme pops up from the tendon as a short sclerite (arculum). It turns distally upon bending of the tibia. The turn of the arculum is several times more than the turn of the tibia, and the arculum is connected to the FCO. This system behaves as a high-pass filter with a time constant close to the step period. Various aspects of the arculum have been studied previously, including its shape in various taxa, its biomechanics, matched neural activity in the FCO, as well as evolutionary aspects. The results of previous studies, published in 1985-2003 in Russian, are inaccessible to most foreign readers. However, original texts and the list of studied species (>350) are now available online. Recently, we minimized the system to three components: the proximal tibial ledge, the tendon and the arculum. The elastic tendon contains resilin. In four model species, the arculum readily turned upon stretching of the tendon. Turning was video recorded. The force of approximately 0.005 N, applied to a tendon approximately 0.25 mm in size, is enough for the utmost turn of the arculum. The arculum turned also upon local deformations close to its base. The ability to turn vanished after incision between the arculum and the distal part of the extensor apodeme. A mechanical model of an amplifier is proposed. The apodeme includes optically active structures, which behave differently in polarized light.

Do enlarged hind legs of male thick-legged flower beetles contribute to take-off or mating?

The volume of the hind femora in adult male flower beetles, Oedemera nobilis, is 38 times greater than in adult females. To determine what advantage limbs with swollen femora might provide, the behaviour of these insects was analysed with high speed videography. First, because large hind legs are often associated with jumping and take-off, the performance of this behaviour by the two sexes was determined. Take-off was generated by a series of small amplitude wing beats followed by larger ones with the hind legs contributing little or no propulsion. The mean acceleration time to take-off was not significantly different in males (46.2 ms) and females (45.5 ms), but the mean take-off velocity of males was 10% higher than in females. Second, to determine if enlarged hind legs were critical in specifically male behaviour, interactions between males and females, and between males were videoed. A male mounted a female and then encircled her abdomen between the enlarged femora and tibiae of both his hind legs. The joint between these leg parts acted like a mole wrench (vise grip) so that when the tibia was fully flexed a triangular space of 0.3 square mm remained in which a female abdomen (cross-sectional area 0.9 square mm) could be compressed and restrained firmly without inflicting damage. The flexor tibiae muscle in a male hind femur was 5.9 times larger than the extensor. In interactions between males, attempts to achieve a similar entrapment were frequently thwarted by the pursued male extending his hind legs vertically.