The extremely long-tongued Neotropical butterfly Eurybia lycisca (Riodinidae): Proboscis morphology and flower handling

Abstract

Few species of true butterflies (Lepidoptera: Papilionoidea) have evolved a proboscis that greatly exceeds the length of the body. This study is the first to examine the morphology of an extremely long butterfly proboscis and to describe how it is used to obtain nectar from flowers with very deep corolla tubes. The proboscis of Eurybia lycisca (Riodinidae) is approximately twice as long as the body. It has a maximal length of 45.6 mm (mean length 36.5 mm ± 4.1 S.D., N = 20) and is extremely thin, measuring only about 0.26 mm at its maximum diameter. The proboscis has a unique arrangement of short sensilla at the tip, and its musculature arrangement is derived. The flower handling times on the preferred nectar plant, Calathea crotalifera (Marantaceae), were exceptionally long (mean 54.5 sec ± 28.5 S.D., N = 26). When feeding on the deep flowers remarkably few proboscis movements occur. The relationship between Eurybia lycisca and its preferred nectar plant and larval host plant, Calathea crotalifera, is not mutualistic since the butterfly exploits the flowers without contributing to their pollination. We hypothesize that the extraordinarily long proboscis of Eurybia lycisca is an adaptation for capitalizing on the pre-existing mutualistic interaction of the host plant with its pollinating long-tongued nectar feeding insects.

The ecological role of extremely long-proboscid Neotropical butterflies (Lepidoptera: Hesperiidae) in plant-pollinator networks

“…L. camara had the shortest nectar spurs (10.4 ± 0.9 mm, N = 11). Whereas both L. camara and S. frantzii received frequent visits from other butterflies, e.g., Pieridae, Nymphalidae, Papilionidae and Lycaenidae, the two species of Calathea were visited exclusively by Hesperiidae and butterflies of the genus Eurybia (Riodiniae), confirming the results of a previous study (Bauder et al 2011).…”

“…Since the butterflies' proboscides are longer than the floral tube, they are not forced to plunge their head into the corolla entrance and successful pollination is very unlikely. Apart from that, previous analyses on the flower-visiting behavior of extremely long-proboscid butterflies (Bauder et al 2011) as well as the results of this study demonstrate that neither skipper nor metalmark butterflies were able to release the trigger mechanism of Calathea-flowers effectively. Schemske and Horvitz (1984) made similar observations and stated that while Hesperiidae accounted for 21 % of all flower visits on Calathea ovandensis, they were responsible for only 2 % of all triggered flowers and less than 1 % of all fruit sets.…”

“…Although our results showed that the proboscis lengths of skipper butterflies differed significantly between the visited flower species, we did not observe a close match between extremely long proboscides and deep tubes: Extremely long-proboscid skipper butterflies that used C. crotalifera and C. lutea as nectar source had a mean proboscis length of 43.4 mm, exceeding the corolla length of C. crotalifera by 18.4 mm and C. lutea by 12 mm. Similarly, the proboscides of E. lycisca butterflies in Costa Rica that fed on the nectar of C. crotalifera and C. lutea plants measured 36.5 mm on average (Bauder et al 2011), exceeding the corolla depth of C. crotalifera and C. lutea by 11.5 or 5.1 mm, respectively. Since the butterflies' proboscides are longer than the floral tube, they are not forced to plunge their head into the corolla entrance and successful pollination is very unlikely.…”

Feeding Kinematics and Nectar Intake of the Honey Bee Tongue

“…Thus the length of honey bees' glossae is crucial for their foraging efficiency. But the movements in insects with extremely long proboscis during feeding are slower than the movements in insects with average-sized proboscis, which will produce exceptionally augmentation of functional costs and reduction of foraging efficiency (Bauder et al 2011). A relatively long proboscis insect also need more space for unfolding of the proboscis and thus some of the extremely long-tongued animals still hover while they are foraging, so extendible mouthparts have advantages for the feeding performance of insects (Krenn et al 2002).…”

A New Species ofEurybia(Lepidoptera: Riodinidae: Eurybiini) from Northeastern Brazil

“…The genus can be further distinguished from Alesa Doubleday, 1847 by the presence of bristle-like scales on the first and second labial palpi segments, and a characteristic long and bifurcate valva (Hall 2003). Eurybia holds the record of the greatest length in butterfly proboscis, up to twice the length of the body in some species (Kunte 2007;Bauder et al 2011). In the pupal stage, the proboscis extends beyond the terminal abdominal segments (Horvitz et al 1987).…”