Abstract
The palm borer moth Paysandisia archon (Burmeister, 1880) (fam. Castniidae) is a large, diurnally active palm pest. Its compound eyes consist of ~ 20,000 ommatidia and have apposition optics with interommatidial angles below 1°. The ommatidia contain nine photoreceptor cells and appear structurally similar to those in nymphalid butterflies. Two morphological ommatidial types were identified. Using the butterfly numbering scheme, in type I ommatidia, the distal rhabdom consists exclusively of the rhabdomeres of photoreceptors R1–2; the medial rhabdom has contributions from R1–8. The rhabdom in type II ommatidia is distally split into two sub-rhabdoms, with contributions from photoreceptors R2, R3, R5, R6 and R1, R4, R7, R8, respectively; medially, only R3–8 and not R1–2 contribute to the fused rhabdom. In both types, the pigmented bilobed photoreceptors R9 contribute to the rhabdom basally. Their nuclei reside in one of the lobes. Upon light adaptation, in both ommatidial types, the rhabdoms secede from the crystalline cones and pigment granules invade the gap. Intracellular recordings identified four photoreceptor classes with peak sensitivities in the ultraviolet, blue, green and orange wavelength regions (at 360, 465, 550, 580 nm, respectively). We discuss the eye morphology and optics, the photoreceptor spectral sensitivities, and the adaptation to daytime activity from a phylogenetic perspective.
Highlights
The palm borer moth Paysandisia archon (Burmeister, 1880) (Lepidoptera: Castniidae) is a large moth native to Uruguay and Argentina
As the female probably does not produce long-range pheromones, to initiate mating, a male must first see a female before it starts displaying its colours at close range, suggesting that the large compound eyes play an important role in intraspecific recognition (Sarto i Monteys et al 2012; Frérot et al 2013; Quero et al 2017; review: Sarto i Monteys et al 2016)
The morphological interommatidial angle is less than a degree centrally (Δφ = 0.8°) and almost doubles laterally (Δφ = 1.4°)
Summary
The palm borer moth Paysandisia archon (Burmeister, 1880) (Lepidoptera: Castniidae) is a large moth native to Uruguay and Argentina. Its caterpillars live in galleries in palm tree trunks. The recent introduction to Europe has had a devastating effect on the decorative palm trees around the Mediterranean Sea and may potentially cause severe problems to the date production in North Africa and the Levant. The adult male and female Paysandisia are diurnally active (Sarto i Monteys et al 2016; Frérot et al 2017). As the female probably does not produce long-range pheromones, to initiate mating, a male must first see a female before it starts displaying its colours at close range, suggesting that the large compound eyes play an important role in intraspecific recognition (Sarto i Monteys et al 2012; Frérot et al 2013; Quero et al 2017; review: Sarto i Monteys et al 2016)
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