A Novel Interception Strategy in a Miniature Robber Fly with Extreme Visual Acuity

Abstract

SummaryOur visual system allows us to rapidly identify and intercept a moving object. When this object is far away, we base the trajectory on the target’s location relative to an external frame of reference [1]. This process forms the basis for the constant bearing angle (CBA) model, a reactive strategy that ensures interception since the bearing angle, formed between the line joining pursuer and target (called the range vector) and an external reference line, is held constant [2, 3, 4]. The CBA model may be a fundamental and widespread strategy, as it is also known to explain the interception trajectories of bats and fish [5, 6]. Here, we show that the aerial attack of the tiny robber fly Holcocephala fusca is consistent with the CBA model. In addition, Holcocephala fusca displays a novel proactive strategy, termed “lock-on” phase, embedded with the later part of the flight. We found the object detection threshold for this species to be 0.13°, enabled by an extremely specialized, forward pointing fovea (∼5 ommatidia wide, interommatidial angle Δφ = 0.28°, photoreceptor acceptance angle Δρ = 0.27°). This study furthers our understanding of the accurate performance that a miniature brain can achieve in highly demanding sensorimotor tasks and suggests the presence of equivalent mechanisms for target interception across a wide range of taxa.Video Abstract

A novel setup for 3D chasing behavior analysis in free flying flies

“…This time the bead moved in straight line, at a computer-controlled speed, with height-adjustable pulley system. A similar study has been performed with robberflies by Wardill et al (2017) and a much smaller aerial predator, the killer fly (Wardill et al, differences result in the major advantage regarding the power required to move the cart carrying a given amount of payload (see below). First, an extra couple of pulleys change the belt circuit, enabling the belt to cross outside of the working range (see Fig.…”

Decision‐making and motor control in predatory insects: a review of the praying mantis

“…Electrical stimulation of TSDNs elicits small movements of the wings that could be interpreted as steering adjustments (Olberg, 2012). Interestingly, the robber fly Holcocephala fusca Bromley shows the pursuing trajectory suggesting interception initially but switches to 'lock-on' phase finally (Wardill et al, 2017). During 'lock-on' phase, the fly fixes its flight speed to a value slightly higher than that of the prey, probably extending the time over which the fly may catch the prey.…”

“…Olberg, 2012), tiger beetles (e.g. Haselsteiner et al, 2014), killer flies (Wardill et al, 2015), and robber flies (Wardill et al, 2017), relatively little is known about their defensive behaviours, except in the mantis. Hence, the mantis is a good model for understanding predatory and defence systems and their interaction.…”

Functional interplay of visual, sensitizing and screening pigments in the eyes of Drosophila and other red‐eyed dipteran flies

“…For instance, whereas the range of the interommatidial angles of the small fruitfly Drosophila is ∼2.5–7 deg (Hardie, ), in the also rather small robber fly, Holcocephala fusca , this range is ∼0.3–5 deg (Wardill et al . ).…”