Category: About

About blockislandmoths.org

Block Island Moths is intended for use both by anyone looking learn about Block Island’s moth fauna and for professional and amateur lepidopterists more generally. This website can serve as a field guide for use by anyone attempting identification of moths found on Block Island, though it would be of more limited use elsewhere in the region, since there are many species commonly found on the mainland and on nearby islands that do not occur on Block Island. If you find moths of any life stage on Block Island, please submit photos to BugGuide or iNaturalist or send them to me at blockislander1@gmail.com for prompt identification and inclusion of any novel species or seasonality records here.

The main section of this website is for moths, with butterflies excluded. However, there are sections for the butterflies and caddisflies of Block Island. The species pages for butterflies lack the phenology graph and distribution map found on the moth species pages, since butterflies are all diurnal and seldom seen at lights. I have recorded caddisflies at lights using the same methodology as for moths, so species pages for Trichoptera include these graphics.

In addition to providing a wealth of information on Block Island’s moth fauna, this website serves as a digital field guide to the island’s moths. There may be no place on Earth with 1,000+ moth species where identification of the local fauna is as easy as it now is on Block Island thanks to this website. Go to the identify section to identify nearly any moth on Block Island using plates of live images.

The phenology data included on the species pages would probably prove instructive for regional comparisons and useful as a guide to species’ flight times to moth observers throughout southern New England. The data on species’ local distribution, combined with the information included on species’ habitat preferences and host plants, could also prove useful as a proxy measure of the distribution of Block Island’s flora. Finally, the summaries of the data gathered at each black lighting site can provide some indication of the most ecologically valuable places on Block Island especially worthy of conservation.

Identification

This section of the Block Island Moths website is intended to be used as a guide to the island’s moth fauna. It is obtimized for mobile browsers to enable easy use on a phone as a digital field guide. The images are organized multiple ways to aid identification.

The taxonomy view displays single images of up to six species in each superfamily, family, genus, or other taxon. In this view, taxa are organized and images selected with ease of use and aesthetics in mind; the ordering therefore differs substantially from both the Hodges (1983) sequence and the phylogenetic order of Pohl, Patterson, and Pelham (2016). Generally, similar taxa are placed together, and the most abundant and diverse taxa are placed near the top. Clicking on a taxon will bring the user to a page displaying images of all local daughter taxa. When a taxon has only one immediate daughter taxon present on Block Island, clicking on it skips to the daughter taxon. When viewing genera, for any genus with only one local species, the species name will be shown. Clicking on it will bring the user to its species page. Clicking on a genus displays an image of each species in the genus; displaying an image of each species for a higher taxon can be done by selecting either of the other two viewing options (see next). The species view displays a single image of each species in a given taxon. The default is for the species to be ordered according to the Pohl et al. (2016) phylogenetic sequence, but the species can instead be displayed in order of abundance in my surveying from 2018 to 2021.

Species Information

The centerpiece of this website is the series of species pages for the more than 1,200 moth species recorded on Block Island. Each page includes representative live photographs; a chart of flight time phenology; a map of Block Island depicting the local distribution of the species; information on host plants, life cycle, identification, and more; and a list of specimens collected on Block Island.

Flight time phenology is represented for most species in three ways, in all cases organized by 1/3-month period (1st to 10th, 11th to 20th, and 21st to end of month) (Fig. 1). All records from photographs, notes, and specimens gathered in the present survey, along with all older records I have found from previous surveying, are used as species presence records. To calculate abundance, I use only my nightly records from my porch lights (the Hunt property), which I began taking in 2018. I have enough records for abundance estimates from late May to early October. Abundance is represented in two ways: as individuals per survey night and as percent of moths of all species.

Flight time phenology is represented differently for species that are rare at the Hunt property but common enough at at least one major black lighting site to create a large sample size. More than half of all my records since 2018 are at the Hunt property, and this is the only site with many survey nights in each 1/3-month period throughout the summer. For species common at the tupelo forest southeast of the airport and/or the site in the north of Nathan Mott Park Preserve west of the airport and/or the site in the south of Nathan Mott Park Preserve near Old Mill Road but rare at the Hunt property, numbers of individuals for each survey night from one or both sites are depicted in a scatterplot, with abundance values for the Hunt property added if informative (Figs. 2–4).

Each species page include a map of Block Island that provides information on the local distribution of the species (Fig. 5). Each map uses my sighting records from the Hunt property and at sheets at sites across Block Island since 2018. The total number of sightings of the species, the percentages of those sightings that occurred in each area surveyed, and the percentages of sightings of all moth species that occurred in each area. While these are crude measures that do not account for seasonality, they are generally informative, especially for common species. Percentage representation of a site for one species that is much lower that of the site for all moths indicates that the species in question is poorly represented at that site relative to elsewhere on Block Island, and higher representation indicates the reverse. Some species are about equally common at sites across the island, while some have been found exclusively at one surveyed site. Refer to site descriptions for information needed to relate a species’s local distribution on Block Island to its possible host plants and habitat requirements.

About the Authors

Surveying the moths of Block Island has been a passion project of mine for the last several years. I began regularly photographing moths in 2014 with no prior experience, and within a few years, photographing, identifying, collecting, and studying moths became my primary preoccupation. I am now a masters student at the University of Delaware writing my thesis about how urbanization shapes moth community composition in and around Boston and Providence. I intend to pursue a PhD next, most likely working on moth systematics.

Nigel Grindley is an emeritus professor of molecular biophysics and biochemistry at Yale University. He and his wife Cathy Joyce are year-round residents of Block Island. I met them in 2015 after Nigel and I found out about our shared interest in moths through BugGuide. Nigel began photographing moths in 2014, around the same time I did and has collaborated with me in surveying the moths of Block Island since the beginning of the project.

Aaron Hunt

Moths constitute one of the most diverse and abundant groups of insects globally and are richly represented in nearly every terrestrial habitat. The most distinctive feature of adult moths and butterflies is the dense, colorful scaling covering nearly the entire body. Moths and butterflies undergo complete metamorphosis, with four distinct life stages: egg, larva, pupa, and adult. The larva, which has up to several pairs of prolegs in addition to three pairs of true legs, is usually called a caterpillar; it produces silk used to build shelters and hang from foliage. In many species, the larva spins a silken cocoon and pupates within it. Adults have two pairs of wings, though these are reduced or absent in females, and more rarely in males, of some species.

Moths and butterflies comprise the order Lepidoptera, one of the four largest insect orders along with Coleoptera (beetles), Diptera (flies), and Hymenoptera (wasps and bees), with over 150,000 described species. In phylogenetic terms, butterflies are one diverse clade of moths; their most recent common ancestor was a moth. Butterflies are usually considered separately from the rest of Lepidoptera (i.e. “moths”) for historical and practical reasons: the adults are exclusively diurnal and by far the most conspicuous and abundant day-flying Lepidoptera. (This division in common names is not reflected in all languages; in French, for instance, all Lepidoptera are papillons.) Butterflies’ diurnal habits, heavy reliance on nectar for food, and vibrant colors in their adult stage have made them the most popular and best-studied group of insects. However, butterflies have not been a focus of the Block Island moth survey due to the popular distinction between them and the rest of Lepidoptera; their already being very well-studied; and, crucially, their diurnal habits, which mean they can’t be studied by surveying with lights.

Survey Methods

Overview

Surveying for moths is most often and easily accomplished by setting lights at night to attract adults. Moths are primarily nocturnal, and most species are attracted to lights, some much more strongly than others. A single bright ultraviolet or incandescent light placed in a rich temperate habitat will reliably attract well over 100 species of moths on on calm, moonless, and warm summer nights. Even in quite degraded and fragmented semi-natural habitats, such as the post-agricultural meadows and shrublands that cover much of Block Island, a light can attract over 100 species of moths on the best nights. While certain moth taxa are diurnal or not attracted to lights, most species present in any given area will come to lights at least occasionally.

Light surveying has been the main method used in the Block Island moth survey, and only a handful of the more than 1,200 species known from Block Island have been recorded on the island only by other survey means. The most conspicuous and diverse group of Lepidoptera not attracted to lights is the butterflies, which comprise a single large diurnal superfamily, Papilionoidea. (Butterflies evolved from moths and from the perspective of cladistics are a group of diurnal moths in the same way birds are therapod [dinosaurs], hominids are apes, and ants are wasps.) Moths are also commonly surveyed by searching flowers on warm sunny days for nectaring diurnal adults, sweeping fields for adults, and searching for larvae on and in plants; I have not utilized these methods as much as I would like so far.

What makes my survey nearly unique among moth surveys is that since 2018, I have made comprehensive records of abundances of all species each survey night, recording more than 40,000 individual moths in four seasons. This dataset allows for quantitative analysis of the fauna, which I have only just begun. For each species, I have generated a flight time phenology chart and a map of relative abundance in each area surveyed. For common species, my observations reliably measure flight times and habitat preferences. My data can also be used to characterize Block Island’s moth fauna in great detail. So far, I have produced measures of the similarity of the fauna between survey locations and, using my observations at my porch lights, its change over the course of the season.

Timeline

The methods, goals, and scope of this survey evolved organically over the course of several years beginning in 2014. This survey began as part of a more general survey of Block Island’s animal fauna I began in August 2014 with no guidance or prior experience in faunal surveying methods or species identification. Over the following few years, moths become nearly the exclusive focus of the project, and the moth component of my survey gradually grew into an effort at a comprehensive survey of Block Island’s moths. I began collecting moths in 2016 but did not intensively collect for identification until 2018. I began blacklighting around the island, collecting smaller microlepidoptera, and counting common species at my porch lights in 2017. In 2018, my survey efforts took close to their definitive form. I regularly set up sheets for blacklighting at sites across the island that summer, recorded all individual moths sighted both at my porch lights at at blacklighting sheets, and intensively collected taxa I could not identify to species by sight. In 2021, I began using no-kill bucket traps to supplement my surveying with sheets, particularly in dunes, where winds slacken enough for surveying with sheets only a few nights each summer. Future plans, aside from additional surveying for moths, include floristic and habitat surveys of each location sampled and a detailed plant inventory of the Hunt property and surrounding area.

I began nightly estimates of species counts at my porch lights in 2017 for a set slate of several dozen common species and species complexes and in 2018 for nearly every species. Certain groups, such as Pero spp. and Eulithis spp., in which the species present on Block Island are difficult to impossible to separate on sight, I have recorded jointly. Some groups I could not personally identify on sight in 2018 or into 2019, notably all Renia spp., and some Acronicta spp., I always photographed and/or collected for later determination. Anything unrecognized I likewise photographed and/or collected. Since 2019, I have always collected each species I have not previously seen. For Coleophora spp. and Blastobasidae, I recorded morphospecies as precisely as I could, though I shortsightedly did not consistently make note of the streaky tan Coleophora spp. in 2019. I have since identified many of these morphospecies in through identification of collected specimens, though probably several of Block Island’s Coleophora species are indistinguishable by sight due their similarity, low contrast patterning, and small size. Aside from the omission of some Coleophora spp. in 2019, I have recorded in some manner all moths seen since 2018.

While the great majority of my survey effort has been with lights, I have searched in daytime for adults of diurnal species on flowers and vegetation and by sweeping meadows and for larvae, especially leafminers. Additionally, Nigel Grindley has regularly photographed and collected moths at lights at his home in the southwest of Block Island for several years, by a remarkable coincidence starting the same year I did. In the last few years, he has also surveyed at sheets with blacklights several years while I have been off the island. By my count, he has found 58 species I have not found, of these, fewer than ten were recorded by previous surveyors, making Nigel’s contribution to the island’s species list quite significant. (He has of course seen several hundred of the species I have seen as well.) His surveying has disproportionately added species that fly only very early or late in the season, when I have rarely been on Block Island.

Recording Sightings

The methodology I have used for counting numbers of each species at my porch lights is roughly as follows: I start by scanning the porch, walls, and eaves for moths and note the species I see on my phone. As I go, I photograph uncommon or otherwise interesting moths and capture specimens I wish to collect, usually for identification. I frequently update estimated numbers of each species based either on spotting specimens that were worn or differently patterned than those previously counted or by scanning the entire area for all examples of a set of species for a more complete count. For especially abundant species, I estimate numbers. While my methodology is highly inexact, especially during the most productive nights, it has been fairly consistent. The time I spend at the porch lights each night varies based on the number of moths present, but during the peak of the season, 45-60 minutes is probably typical.

During blacklighting sessions, I follow a similar procedure to that I employ at my porch lights, except in that I spend most or all of the night observing moths until I take down the sheets. When I use two sheets, as I typically do, I record moths separarately at each sheet. I make multiple visits to each sheet each night, and I often note the moths I see flying past when walking between the sheets. My notes on moth found away from the sheets have informed my understanding of which common species are poorly drawn to lights. My typical procedure for counting individuals of a species at a sheet is to quickly but thoroughly scan each side of the sheet and then any nearby plants as well as the ground, continually scanning the sheet and updating counts as long as the total number of individuals present appears to be increasing. As at the porch lights, I use photography and collection to fill all gaps in the data created by identification uncertainty, excepting certain species complexes.

Data Analysis

At the end of each season, I compile all my sighting records into a single document in chronological order. I manually add my sightings to a spreadsheet with a line for each species and a column for each night or blacklighting sheet (Fig. 1). Records of unidentified species are marked in red and with asterisks and revisited when I identify the species they represent. I add photographic and specimen records, not all of which I include in my nightly notes, to my tables to complete my records.

I use a series of spreadsheets to store all my photographic records from 2017 and earlier, Nigel’s photographic records, and records from older surveys; and I use these along with my 2018–2021 sighting tables to make a single table with presence/absence data for each species in each 1/3-month period from March through December (Fig. 2). I use the sighting records from my porch lights from 2018 to present to calculate flight time phenology in individuals per survey night and as a percent of all moth records for each 1/3-month period (Fig. 3).

Partial List of Relevant Survey Data and Other Research

This page will eventually have an explanation of how best to identify moths along with the principles of species identification generally. For now, it has two collages illustrating intraspecific variability in forewing markings.