Measuring proboscis length in Lepidoptera: a review

Abstract

Mouthpart morphologies relate to diet range. Differences among or within species may result in resource partitioning and speciation. In plant-pollinator interactions, mouthpart length has an important role in foraging efficiency, resource partitioning and pollination, hence measuring nectarivorous insect mouthparts’ morphological variation is important. Most adult lepidopterans feed on nectars and participate in pollination. Although a vast range of studies applied morphometric measurements on lepidopteran proboscis (tongue) length, general recommendations on methodologies are scarce. We review available proboscis length measurement methodologies for Lepidoptera. Focusing on how proboscides have been measured, how accurate the measurements were, and how were these constrained by sampling effort, we searched for research articles investigating lepidopteran proboscis length and extracted variables on the aims of measurements, preparation and measurement methodology, and descriptive statistics. Different methods were used both for preparation and measurements. Many of the 135 reviewed papers did not provide descriptions of the procedures applied. Research aims were different among studies. Forty-four percent of the studies measured dead specimens, 13% measured living specimens, and 43% were unclear. Fifteen percent of the studies used callipers, 9% rulers, 1% millimetre scales, 4% ocular micrometers, 3% drawings and 14% photographs; 55% were non-informative. We emphasise the importance to provide detailed descriptions on the methods applied. Providing guidelines for future sampling and measurements, we encourage fellow researchers planning measurements to take into account the effect of specimen preparation techniques on the results, define landmarks, consider resolution, accuracy, precision, choose an appropriate sample size and report details on methodology.

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

“…The material properties of insect structures play an important role in their functionality [18,21,59]. Elasticity of the insect cuticle, for example, is often associated with the presence or absence of resilin [22,50,60]. Here, we found flower visitors with few sensilla styloconica, such as A. precationis and C. agitatellus , had a drinking region with extensive red autofluorescence (red was assigned to autofluorescence signals from excitation lasers 561 and 640 nm), an indicator of high amounts of sclerotization.…”

“…Studies of insect mouthparts have become more interdisciplinary, often involving fields that span morphology [8][9][10], biomechanics [11][12][13], developmental biology [14,15], material sciences [16][17][18] and chemistry [19][20][21]. Although mouthparts have been studied from an array of insect lineages, the lepidopteran proboscis has notably experienced an increase in study abundance [22], likely due to their large biodiversity, important role as pollinators, and interesting feeding mechanism that is capable of transporting nanolitres of liquids from wetted surfaces to the gut [23].…”

Automated Size Measurements of Halyomorpha halys (Stål) (Heteroptera: Pentatomidae) with Simple Image-Based Methodology

“…However, existing methods for insect measurement often are labor-and time-intensive, and rely on the experience and precision of the individual performing measurements. Additionally, standardized methods for insect measurements often do not exist, such as the case for proboscis length in Lepidoptera (Vajna et al 2021) leading to difficulty in comparing results among studies. Recently, new techniques have emerged to improve accuracy of size measurements including high resolution digital photography which have been used to measure live and dead Phormia regina (Meigen) (Diptera: Calliphoridae) larvae (Bourne et al 2019).…”