Evolutionary functional morphology of the proboscis and feeding apparatus of hawk moths (Sphingidae: Lepidoptera)

Abstract

The morphology of the proboscis and associated feeding organs was studied in several nectar-feeding hawk moths, as well as a specialized honey-feeder and two supposedly nonfeeding species. The proboscis lengths ranged from a few millimeters to more than 200 mm. Despite the variation in proboscis length and feeding strategy, the principle external and internal composition of the galeae, the stipes pump, and the suction pump were similar across all species. The morphology of the smooth and slender proboscis is highly conserved among all lineages of nectar-feeding Sphingidae. Remarkably, they share a typical arrangement of the sensilla at the tip.The number and length of sensilla styloconica are independent from proboscis length. A unique proboscis morphology was found in the honey-feeding species Acherontia atropos. Here, the distinctly pointed apex displays a large subterminal opening of the food canal, and thus characterizes a novel type of piercing proboscis in Lepidoptera. In the probably nonfeeding species, the rudimentary galeae are not interlocked and the apex lacks sensilla styloconica; galeal muscles, however, are present. All studied species demonstrate an identical anatomy of the stipes, and suction pump, regardless of proboscis length and diet. Even supposedly nonfeeding Sphingidae possess all organs of the feeding apparatus, suggesting that their proboscis rudiments might still be functional. The morphometric analyses indicate significant positive correlations between galea lumen volume and stipes muscle volume as well as the volume of the food canal and the muscular volume of the suction pump. Size correlations of these functionally connected organs reflect morphological fine-tuning in the evolution of proboscis length and function.

Wettability and morphology of proboscises interweave with hawkmoth evolutionary history

“…Nectar feeding has evolved multiple times independently across insects, but hawkmoths have the longest proboscises relative to body size among all insects ( Hutchinson et al, 2018 ; Reinwald et al, 2022 ). The co-evolution between proboscis length and floral nectary tubes is frequently evoked to explain why proboscises have elongated.…”

The Morphology of the Sensilla on the Proboscis of Aporia crataegi (Linnaeus, 1758) (Lepidoptera: Pieridae)

“…suroia (Nymphalidae), ~44 µm in L. celtis (Nymphalidae) (Ma et al, 2019). Reinwald et al (2022) (Rothschild & Jordan, 1903) (Sphingidae). Microtrichia observed on the surface of the galea are common on the proboscis and are likely to act as mechanical receptors (Molleman et al, 2005).…”

Diverse material properties and morphology of moth proboscises relates to the feeding habits of some macromoth and other lepidopteran lineages

“…Most investigations of proboscis morphology have focused on diurnal butterfly species [36][37][38], vampire moths (Noctuidae) [39][40][41], or long-proboscis species, such as sphinx moths (Sphingidae) [42][43][44] and some metalmark butterflies (Riodinidae) [45,46]. Most lepidopteran species, however, are represented by small-to medium-sized nocturnal moth species, thus resulting in a taxonomic bias in the literature and large gaps in knowledge about proboscis morphology and its evolution among lepidopteran lineages.…”