What goes up must come down Biomechanical impact analysis of jumping locusts

Abstract

This study shows new impact behaviour for locusts during uncontrolled landing. There 5 are both passive and active mechanisms involved. Different key parameters affect the landing performance. AbstractMany insects are able to precisely control their jumping movements. Previous studies have shown that many falling insects have some degree of control of their landing-orientation, indicating a possible 10 significant biomechanical role of the exoskeleton in air righting mechanisms. Once in the air, the properties of the actual landing site are almost impossible to predict. Falling insects thus have to cope mostly with the situation at impact. What exactly happens at the impact? Do locusts actively 'prepare for landing' while falling, or do they just 'crash' into the substrate?Detailed impact analyses of free falling Schistocerca gregaria locusts show that most insects 15 typically crashed onto the substrate. There was no notable impact-reducing behaviour (protrusion of legs, etc.). Independent of dropping angle, both warm and cooled locusts mostly fell onto head and thorax first. Our results also show that alive warm locusts fell significantly faster than inactive or dead locusts. This indicates a possible tradeoff between active control vs. reduced speed. Looking at the morphology of the head-thorax connection in locusts, we propose that the anterior margin of the 20 pronotum might function as a 'toby collar' structure, reducing the risk of impact damage to the neck joint. Interestingly, at impact alive insects also tended to perform a bending movement of the body. This biomechanical adaptation might reduce the rebound and shorten the time to recover. The adhesive pads also play an important role to reduce the time to recover by anchoring the insect to the substrate.

Many ways to land upright: novel righting strategies allow spotted lanternfly nymphs to land on diverse substrates

“…This interpretation is supported by our finding that, in spite of impacting the surface with similar speeds and orientations, live SLF nymphs finally landed upright significantly more often than dead specimens, even those with legs spread. To understand this phenomenon, we first note that almost all live and dead specimens bounced after impact so as to dissipate most of their pre-impact energy (greater than 97% for live and greater than 94% for dead specimens), similar to values reported for crash-landing locusts (76%) [29] and cockroaches running into walls (95%) [37]. This is important because nymphs benefit from dissipating most of their kinetic energy quickly in order to land securely, while retaining enough kinetic energy to surmount potential energy barriers that can prevent the reorientations required for righting [7].…”

“…Insects maintained in this way retained their normal levels of activity for at least 48 h. Because this species is the subject of an eradication programme [28], all specimens were euthanized by freezing after experimentation. For studies of dead specimens, we used frozen insects that were thawed and either used within 30 min of thawing or stored in 49% relative humidity chambers to avoid desiccation and to preserve their native biomechanical properties [29]. Specimen body length, L = 11.8 mm [10.3, 12.6] mm (mean, range) (figure 1b), was measured to ±0.05 mm either using digital calipers (model SV-03-150, E-base Measuring Tools, Yunlin, Taiwan) or using the measure function in ImageJ [30] on digital photographs including a millimetre-ruled scale.…”