by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
As part of the recent Nantucket Biodiversity Assessment Week program, we set up a couple of moth sheets at the field station and used two different types of lights (UV or “black lights” and mercury vapor lights) to attract the evening beauties to the sheets to be photographed. This is the second time we’ve done this for the public out at the Field Station and we’ll be doing this on a regular basis as part of a slowly evolving Massachusetts Natural History Survey. So you could say I have moths on the brain and figured now was a good time to learn more about them.
Moths belong to the large order Lepidoptera which also includes butterflies. Lepidoptera is one of the most widespread and widely recognizable insect orders in the world, encompassing 46 superfamilies, 44 of which are moths, and one each for butterflies and skippers. The term was coined by Linnaeus in 1735 and is derived from Ancient Greek “lepidos” meaning scales and “pteron” meaning wing. Comprising an estimated 174,250 species, the Lepidoptera show many variations of the basic body structure that have evolved to gain advantages in lifestyle and distribution. Recent estimates suggest that the order may have more species than earlier thought, and that it is the second largest order among the four most speciose orders, which include the Hymenoptera (sawflies, wasps, bees and ants), Diptera (“true flies” including mosquitoes, gnats, midges), and the Coleoptera (beetles, most numerous, comprising almost 25% of all life forms). As we can see with such a large number of species, moths are an amazing evolutionary success. That’s not even counting Mothra, who starred in at least 17 movies and was depicted with a combination of butterfly and moth characteristics just to confuse scientists.
Many moths are highly dependent on certain types of habitats and our island conservation of essential habitat like sandplain grasslands means that we are able to see some of the species that are becoming rarer on the mainland. All moths undergo complete metamorphosis; that is, their life cycles progress through egg, larval, pupal, and adult stages. Thus, the typical moth lives two very different lives, filling two distinct ecological niches; it is born as a terrestrial, vegetarian machine and is “reborn” as a winged creature of the night, intent on completing its reproductive cycle.
How do you tell the difference between a moth versus a butterfly? Both of them may be seen in the daytime, so the time of day you see them is not as much help as you would think. Sometimes you can distinguish them by their feelers, or antennae. Most butterflies have thin filament-like antennae that are club-shaped at the end. On the other hand, many (but not all) moths have comb-like or feathery antennae. This distinction is the basis for the earliest taxonomic divisions in the Lepidoptera – the Rhopalocera (“clubbed horn,” the butterflies) and the Heterocera (“varied horn,” the moths). There are, however, exceptions to this rule and some moths (for example, Castniidae) have clubbed antennae. Some butterflies, like Pseudopontia paradoxa from the forests of central Africa, lack the clubbed ends.
The majority of butterflies are active during the day while moths are active mostly at night. It helps to bear in mind that butterflies are essentially diurnal (daytime) moths, the way bees are vegetarian wasps or whales are mammals.
Moths are extremely adept at using smell to locate a mate and many species have well developed olfactory organs. The feathered antennae of male moths from the Saturniidae, Lasiocampidae and many other families are so sensitive that they can detect the pheromones of female moths from distances of 2. 0 km (1.2 miles) and perhaps even up to 11 km (6.8 mi) away (http://www.cs.csubak.edu/~wli/Wei_Li_Pub/Adaptive_01Li.pdf ). Female moths can detect a male’s age, ancestry and possibly reproductive health by pheromones; I’ll leave any comparisons to human abilities alone (http://www.youramazingbrain.org.uk/supersenses/pheromones.htm).
Both butterflies and most moth species have mouth parts called proboscises. The more “primitive” moth members in the Micropterigidae family do not have these developed mouth parts, but have mandibles instead. Some ephemeral species, such as the Luna moth, also do not have any functional mouthparts since their adult lifespan is very short and they don’t waste their limited time on Earth finding something to eat. The Convolvulus Hawk-moth has a proboscis 14 cm long, which it keeps coiled up ready to dip into the trumpet shaped convolvulus flowers that it takes nectar from. There are a few species of moths found in Madagascar and Africa that drink tears! They use a long proboscis armed with hooks like a harpoon to slip under the eyelids of sleeping birds and other mammals. Scientists think they may be getting salt and proteins from tears. I had to look up about five corroborating articles before I believed this one. (Biology Letters (DOI: 10.1098/rsbl.2006.0581). The term for this is lachrymophagy in case you need it for a sad song or poem. And if that isn’t enough for you, there are also some moths that drink blood. I think a new Twilight book that includes Mothman should be explored.
Many moths have “ears” that can detect sound waves. They developed this ability to avoid becoming dinner for bats. Some butterflies also have sound organs on their legs; different groups of Lepidopterans have evolved sound-detection organs independently on different body parts.
- Body Temperature Regulation: Butterflies use the sun to warm up. The more typically nocturnal moths must depend on moving their wings to stay warm.
- Pupa: Most butterflies make a chrysalis hanging from a branch or other support while moths often pupate with a cocoon or underground.
- Color: This may be a bias of the butterfly crowd, but most butterflies are brightly colored while moths are typically less conspicuous than butterflies. But they have better personalities I’m told.
- Wing venation: All butterflies and moths ( except plume moths ) have 2 pairs of overlapping wings, each comprised of a very thin double membrane with rigidity supplied by a network of tubular veins radiating from the base of the wings. The pattern of veins differs in each group of butterfly, and is one of the main sources of characteristics used by taxonomists when identifying and classifying them. Differences between moth and butterfly venation help scientists differentiate among the 120+ different families of butterflies and moths.
Male moths can often be distinguished from females by their broader, comb-like antennae, valve-like abdominal claspers, and smaller, more slender bodies. How do you tell different very similar looking moths apart? Well, believe it or not, by their genitals. I bet you didn’t know that. I had the pleasure to visit Cape and Islands moth expert Dr. Paul Goldstein at his office in the Smithsonian’s National Museum of Natural History in Washington DC back in March. I was amazed at the rows and rows of cabinets filled with preserved moths used as voucher specimens to document species found all over the world. And low and behold, there are cabinets filled with, you guessed it, moth genitalia (the more common word rhymes with what is known by chemists as naphthalene– which is a prevalent moth collection smell) that scientists use to tell the tiny creatures with fewer other defining features apart. I am pretty sure they don’t tell you that in zoology class. In fact, several species of both small and large (micro and macro) moths can only be identified by dissecting their genitalia or by their caterpillars or their DNA. And sometimes the most reliable way to positively identify a micro moth is to rear it in captivity. So when you are observing and caring for cocoons and chrysalises you are using a method still used by many researchers around the world to better understand Lepidoptera.
Moths are one of our most beautiful and underrated creatures here on Nantucket. The Field Station has been fortunate to facilitate long term research on moths of Nantucket by Mark Mello, the Director of Research at the Lloyd Center for the Environment. Mark did surveys on the island in response to some proposed development projects. It is important to remember when we are looking for state listed species that have certain protections, we are in fact trying to preserve the habitat they use in cases where only one or two habitats will do. He was able to compare his findings to earlier research conducted by Frank Morton Jones and Charles P. Kimball which is described in their 1943 publication, “The Lepidoptera of Nantucket and Martha’s Vineyard Islands, Massachusetts”. This publication includes the moth data from Charles William Johnson’s 1930 pioneering publication, “A list of the Insect Fauna of Nantucket Massachusetts”. Both of these works were publications of The Nantucket Maria Mitchell Association and provided an excellent opportunity to see how moth populations have varied over time and a changing landscape. Mark Mello has created an online database to compare his surveys to earlier surveys over the past 100 years while providing ecological data and images on Nantucket’s moth fauna (http://lloydcenter.org/nantucket-lepidoptera/, accessed June 3, 2012).
According to the Lloyd’s center Lepidoptera page listed above: “Over sixty percent (24 out of 39) of the rare moth fauna listed in the Massachusetts Endangered Species Protection Act are found primarily in scrub oak barrens (9 species), coastal heathlands (8 species), or sandplain grasslands (7 species). Forty-four percent (17 of 39) are restricted to native heathland or shrubland (including scrub oak barrens) habitat as described by Wagner et al (2003); and this number represents only a fraction of the 56 species of “Conservation Concern” they list as uncommon shrubland/heathland specialists. For New England, many of these species reside in, and in some cases are restricted to, southeastern Massachusetts – particularly Martha’s Vineyard and Nantucket. In fact, the sandplain grassland, coastal heathland and scrub oak habitats on Massachusetts offshore islands have been identified as significant globally rare natural communities (Swain & Kearsley, 2000).” The report goes on to state that: “Thus, of the 24 state-listed macrolepidoptera recorded on Nantucket, only 14 species (58%) were recorded both by Kimball and by Mello. This change in state-listed species composition was similarly reflected in the entire macrolepidopteran fauna (excluding butterflies). Of the 738 species that have been documented on Nantucket by Kimball (575 species) and Mello (618 species) through 2006, only 455 species (62%) were documented by both researchers. Mello has documented 163 species not seen by Kimball, and conversely 120 species were not found between 2000 and 2005. This change in over a third of the recorded moth fauna on Nantucket was not anticipated by Kimball, but it reflects the changes in vegetation that have taken place on the island.”
The significant work on island by the Nantucket Conservation Foundation, the Nantucket Land Bank and Massachusetts Audubon among others has helped preserve some of these populations from disappearing as grasslands give way to shrublands and eventually forests. In future articles we’ll explore what other plant and animal populations are supported by these habitats.
Sadly, it seems like most web sites are concentrating on the dreaded winter moth and not its many helpful, beautiful and native cousins. Their biggest concern in New England is the winter moth (Operophtera brumata) which is an introduced pest that has been well established in Eastern Massachusetts and Rhode Island for about 10 years. It favors oaks, maples, birches, apple, crabapple, blueberry and other deciduous hosts here. It also is one of the first caterpillar pests to hatch from over-wintering eggs in the early spring; usually just prior to bud-break as host plant buds are swelling. If many caterpillars are able to emerge and feed on buds in their delicate first flush, then significant plant damage can occur. (http://www.capecodextension.org/docs/natural%20resources/Winter_Moth_Release.pdf, accessed June 3, 2012.)
I can’t recommend highly enough the daily dose of beautiful moth pictures I get through a free subscription to “Bug of the Day” by my friend Dr. Jenn Foreman-Orth. Every day she sends out a beauty captured on her back porch moth sheet (an example of her work can be found at http://www.flickr.com/photos/urtica/ and you can sign up for Bug of the day here http://www.flickr.com/photos/urtica/collections/72157600071443705/. Jenn will be here in August with fellow moth expert Dave Small to do a mini moth bioblitz concentrating on some of the micro species sometimes ignored in other surveys. If you are on island August 4-8th, come out to the field station to check out our process. No moths will be harmed; the research is done by collecting fine scale macro photos of each species we see. Hopefully you have learned a thing or two about moths and will appreciate them more when you see them.
Resources used for this article:
Powell, Jerry A. (2009). “Lepidoptera”. In Resh, Vincent H.; Cardé, Ring T. Encyclopedia of Insects (2 (illustrated) ed.). Academic Press. pp. 557–587. ISBN 978-0-12-374144-8. Retrieved 3 June 2012.
Mallet, Jim (12 June 2007). “Taxonomy of Lepidoptera: the scale of the problem”. The Lepidoptera Taxome Project. University College, London. Retrieved 3 June 2012.
An excellent online article by Robert A. Raguso and Mark A. Willis; http://www.desertmuseum.org/books/nhsd_moths.php. Retrieved 3 June 2012.
Thanks are due to Dr. Paul Goldstein for assistance with this article; anything correct is a result of his input, something wrong is more likely my fault.