Adaptations for nectar-feeding in the mouthparts of long-proboscid flies (Nemestrinidae: Prosoeca)

Abstract

The insects with the longest proboscis in relation to body length are the nectar-feeding Nemestrinidae. These flies represent important pollinators of the South African flora and feature adaptations to particularly long-tubed flowers. The present study examined the morphology of the extremely long and slender mouthparts of Nemestrinidae for the first time. The heavily sclerotized tubular proboscis of flies from the genus is highly variable in length. It measures 20-47 mm in length and may exceed double the body length in some individuals. Proximally, the proboscis consists of the labrum-epipharynx unit, the laciniae, the hypopharynx, and the labium. The distal half is composed of the prementum of the labium, which solely forms the food tube. In adaptation to long-tubed and narrow flowers, the prementum is extremelyelongated, bearing the short apical labella that appear only to be able to spread apart slightly during nectar uptake. Moving the proboscis from resting position under the body to a vertical feeding position is accomplished in particular by the movements of the laciniae, which function as a lever arm. Comparisons with the mouthparts of other flower visiting flies provide insights into adaptations to nectar-feeding from long-tubed flowers.

Time management and nectar flow: flower handling and suction feeding in long-proboscid flies (Nemestrinidae: Prosoeca)

“…The mouthpart morphology suggests that Nemestrinidae are suction feeders that rely on pressure gradients within the proboscis (Karolyi et al 2012). While feeding, on the first microlevel, paired labella at the tip of the proboscis function as a nanosponge.…”

Functional constraints on the evolution of long butterfly proboscides: lessons from Neotropical skippers (Lepidoptera: Hesperiidae)

“…Nectar is commonly regarded as the world's most ubiquitous food source and therefore favoured by many birds, bats and insects (Nicolson, ). These taxa have independently evolved various physiological, morphological and behavioural specializations as adaptations for nectar uptake (Pellmyr, ; Muchhala & Thomson, ; Johnson & Anderson, ; Karolyi et al ., , ). Most conspicuous are elongations of the mouthparts which are often shaped as a proboscis in insects (Krenn et al ., ).…”

“…Most conspicuous are elongations of the mouthparts which are often shaped as a proboscis in insects (Krenn et al ., ). Euglossine bees, certain tabanid and nemestrinid flies and some hawk moths have evolved extremely long mouthparts that exceed twice the body length to gain access to long‐tubed flowers (Amsel, ; Borrell, ; Borrell & Krenn, ; Pauw et al ., ; Karolyi et al ., , ). However, such extremely long mouthparts are rare among butterflies.…”

The first fossil hilarimorphid fly (Diptera: Brachycera)

“…Unfortunately it is not possible to determine the morphology of the distal part of the hypopharynx and laciniae in Cretahilarimorpha and to compare them to the situation in Asilidae (see Hull, 1962). Nevertheless the mouthparts of Cretahilarimorpha are very similar to those of the modern Nemestrinidae, Bombyliidae, or the nectar-feeding Syrphidae (see Gilbert, 1981;Szucsich and Krenn, 2000;Karolyi et al, 2012), rather than to the blood-feeding structures of the modern muscid Stomoxys. In particular Cretahilarimorpha differs from Stomoxys in the absence of teeth at the apex of the labella (see Fig.…”