Shear strength calculation of claw tip in attachment system of plague locust Locusta migratoria manilensis

Abstract: Plague locusts control is an important aspect in agricultural production, and the conventional method generally used for controlling locust plague is spraying pesticide. This method can quickly and effectively kill the plague locusts to prohibit the agricultural plants from being destroyed, but will result in serious environmental pollution ascribing to the pesticide residues. Many researchers have exerted their efforts to explore innovative methods to not only control the plague locusts, but also avoid the pesticide pollution. The photoelectric technology, i.e. inducing slippery trapping plague locust based on the phototaxis property of locust has been put forward. This technology relies on the spectrum light source to induce plague locusts, as well as depends on the slippery trapping plate and its related mechanical structure to make the trapped locusts in light source district effectively slide to corresponding equipment. In this technology, one of the most important aspects is developing slippery trapping plate with excellent slip function, which can greatly improve the trapping efficiency of photoelectric inducing machine for trapping plague locust. To acquire material strength properties of claw tip of plague locust used for guiding the selection of trapping plate materials, the shear forces of foreleg, mid-leg and hind-leg claws of the locust (Locusta migratoria manilensis) were measured with insect micro-force measurement system designed in this paper. Utilizing scanning electron microscopy (SEM), microstructures and geometrical properties of the claw tips and their fracture sections were observed and analyzed, and sectional areas of the fracture sections were calculated with obtained SEM images and CAD (Computer-aided Design) software. Based on the acquired values of shear force and sectional area, the shear strength of locust claw tip was calculated. The results presented that the shear forces of locust claw tips were between 197.4 mN and 243.6 mN, and claw tips in forelegs exhibited the greatest value (243.6 ± 8.5 mN), whereas claw tips in mid-legs presented the smallest value (197.4 ± 8.9 mN), and the shear force of claw tips of hind-legs possess moderate value (215.3 ± 19.7 mN). The claw tips of forelegs, mid-legs and hind-legs of locust attachment system presented rather smooth surface and resembled a hemisphere at high magnifications, and these claw tips exhibited similar morphologies and structures but differed in geometrical dimensions. SEM images involving the fracture sections of locust claw tips indicated that the interior of the claw tips possessed composite multilayer structure which consisted of exocuticle and endocuticle. Section areas of the fractured claws had different values, and section area of the fractured claws in forelegs exhibited the smallest value (1 0847.6 ± 770.6 μm2), whereas the section areas of the fractured claws in mid-legs and hind-legs presented the greatest value (13 908.5 ± 825.7 μm2) and moderate value (12 664.5 ± 986.8 μm2), respectively. This obvious discrepancy of sectional areas presumably resulted from the difference of fracture positions. Based on the obtained shear force and section area, the shear strength of the claw tips was calculated, and the results demonstrated that the shear strength of claw tips in locust forelegs exhibited the value of (22.5 ± 1.5 )MPa, whereas the shear strengths of claw tips in locust mid-legs and hind-legs were( 14.2 ± 1.6 )MPa and (17.1 ± 2.1) MPa, respectively. The results here provide valuable information for developing locust trapping plate possessing excellent slip function, and probably promote the development of photoelectric technology of inducing slippery trapping plague locust.