Frequently Asked Questions

  1. What is the life cycle of a moth? Back to top

    Moths go through a process called complete metamorphosis, which is a complicated process that is peculiar to many insects, including moths and butterflies, beetles, flies, wasps, and bees. A female moth lays an egg that hatches to produce a caterpillar (larva). The caterpillar feeds on a plant and grows very rapidly, occasionally shedding its outer skin (exoskeleton) so that it can continue to grow. This process of shedding an old exoskeleton is called molting. Before transforming into an adult, the caterpillar molts to form a pupa, which is often covered in a protective cover of silk, called a cocoon. Within the pupa, the body is transformed into the adult moth, which will eventually emerge, expand its wings, and fly away.

  2. What are the differences between moths and butterflies? Back to top

    ‘Butterfly’ and ‘moth’ are common names applied to members of a group of insects called the Lepidoptera. In general, butterflies have thin, hair-like antennae with a small knob or ball at the end, while the antennae of moths are varied in appearance, often hair-like (with no knob) or feathery. Many moths spin a cocoon of silk as a protective cover for the pupa, while most butterflies do not have a cocoon around their pupa (which for butterflies is often called a chrysalis). In addition, butterflies tend to have brighter colors and patterns and are active during the day, while moths tend to have dull, drab colors and are mostly active during the night. However, keep in mind that there are exceptions to all of these characteristics!

  3. Are all moths nocturnal? Back to top

    While most moths are active during the night (nocturnal), some are active during the day (diurnal). Diurnal moths are often more brightly colored and tend to look a little more like a butterfly, but without a knob at the end of each antenna. Good examples of day-flying moths are those in the genus Hemileuca, which are sometimes called sheep moths (Family Saturniidae). There are also a number of small, micro-moths that are day active.

  4. Do all moths spin cocoons? Back to top

    Many species cover the pupa with a cocoon of silk or a combination of silk and plant debris, such as dead leaves, that they spin in with the silk. However, some moths do not make a cocoon and simply form a naked or exposed pupa. One very famous moth, the silk moth (Bombyx mori), covers its pupa with the silk that people use to make clothing. This moth does not live in the United States and, in fact, can only be found in facilities where they are reared for silk production – it no longer occurs in the wild!

  5. What is the largest moth in the Pacific Northwest? Back to top

    The largest moths in the Pacific Northwest are in the family Saturniidae and are sometimes called Giant Silk Moths. Some, such as the Polyphemus Moth (Antheraea polyphemus) can have wingspans of up to 6.5” (16.5cm)! Some of the hawk moths in the family Sphingidae are also quite large and have very heavy bodies. The largest of these are the Big Poplar Sphinx Moth (Pachysphinx modesta) and the Western Poplar Sphinx Moth (Pachysphinx occidentalis) with wingspans of up to 5.5” (14cm). At the opposite extreme, some micro-moths have wingspans of less than 2 millimeters!

  6. How long do moths live? Back to top

    The length of time for a moth to complete its life cycle from egg to adult varies, depending on the species of moth and time of year. Moths can be univoltine (one generation per year), bivoltine (two generations per year) or multivoltine (with several generations per year). In the Pacific Northwest, most of our moths are uni- or bivoltine. For example, a univoltine moth may lay eggs during the summer, the eggs will hatch, and the larvae will feed on vegetation until they are fully developed, at which time they may bury themselves in the ground, a few inches below the surface. The larva may molt into a pupa (with or without cocoon) in the fall, and will spend the entire winter and spring in that stage. Alternatively, some species overwinter as a larva, which will then pupate in late winter or spring. Either way, in the following spring or summer, the adult moth will emerge and the cycle will be repeated. At this time, the adult moth may only live a few days to a month or so, on average. Other univoltine species, such as fall-flying species, may overwinter as eggs, and there are even some that overwinter as adults. In species that produce several generations each year, the period that it takes to go from the egg to the adult may be as short as 30 days. Still, whatever stage is the one in which the species overwinters will usually be the longest lasting.

  7. What are the worst pest moths in the region? Back to top

    The larvae of almost all moths feed on plant parts, including leaves, stems, twigs and branches, flowers, fruits, or roots, but few are serious pests. However, some moth larvae are among the most serious pest insects in the Pacific Northwest. Perhaps the most economically damaging of these is the larva of the codling moth (Cydia pomonella), which feeds in fruits including apples. This species belongs to a family of small moths (Tortricidae) that is not featured on our website. Other orchard pests include the tent caterpillar moths, including the Western Tent Caterpillar Moth (Malacosoma californicum). Major pests of field crops and ornamental plants include our many species of loopers, cutworms, and armyworms, including the Alfalfa Looper (Autographa californica), the Variegated Cutworm Moth (Peridroma saucia), and the Western Yellowstriped Armyworm Moth (Spodoptera praefica). Serious pests of forests include the caterpillar of the Douglas Fir Tussock Moth (Orygia pseudotsugata) and the Pandora Pinemoth (Coloradia pandora).

  8. What do caterpillars and moths eat? Back to top

    Almost all moth larvae (caterpillars) feed on some form of a plant, from the leaves to the roots. Some species eat only a small number of different plant species, but others eat a huge variety of plants.  As adults, moths feed on water, plant nectar, rotting fruit, and sap from wounded trees. Watch for moths sticking their proboscis (tongue) into a flower to obtain nectar. And, if you look on the plants in your yard or in a patch of weeds, you will certainly see some moth larvae feeding.

  9. What roles do moths play in the environment? Back to top

    Moths and their larvae provide food for other insects, birds, reptiles and amphibians, fish, and mammals. At some times, they are the main food items of these animals. Because of what they eat, and what eats them, caterpillars and moths are extremely important components of most environments. Occasionally, some species can develop outbreaks, in which they become extremely abundant. These outbreaks cause defoliation (the total loss of leaves) of entire trees, and can weaken the trees in a forest or kill large numbers of them. The Douglas Fir Tussock moth (Orygia pseudotsugata) is a good example of a moth species that can defoliate large areas of forests in the Pacific Northwest.

  10. Are there any threatened or endangered moths in the Pacific Northwest? Back to top

    The only moth species listed as threatened or endangered in the Pacific Northwest are Anarta edwardsii and Copablepharon fuscum, both of which are considered Endangered in B.C., where they are at the northern limits of their ranges.  Neither of these coastal species is listed as threatened or endangered in the U.S.

    In many cases, how common or rare a species is depends on how many different types of plants the larvae can eat. For example, the larvae of some species of moths feed on a large number of different types of plants that are available throughout the spring and summer. These species usually occur all summer, and often in large numbers. Other moth species have caterpillars that can feed and survive on only one species of plant. If that plant is rare or is found in a limited area, such as a plant that lives only in bogs, the moths that depend on it will also be rare or limited in distribution. These are the types of moths that most need to be monitored, so we can make sure not to eliminate their host plants or the habitats in which the host plants occur.

  11. Which moths are endemic to (only found in) the Pacific Northwest? Back to top

    Most species on our website have broad geographic ranges that extend outside of the Pacific Northwest, but some have never been found outside of our region. Indeed, these endemic species generally have limited distributions even within the Pacific Northwest.

    Species restricted to the Haida Gwaii archipelago:  Lasionycta haida 

    Species found only around the Gulf of Georgia:  Grammia complicata, Xestia verniloides, Copablepharon fuscum 

    Species that are limited to western Washington and western Oregon:  Ceranemota crumbi

    Species restricted to the Coast Range of B.C.:  Euxoa apopsis, Lasionycta caesia, Lasionycta gelida, Lasionycta macleani 

    Species found only the northern mountains of the Pacific Northwest:  Euchalcia borealis 

    Species limited to the Columbia Plateau:  Euxoa emma, Sympistis apep, Sympistis parvacana, Copablepharon columbia, Copablepharon mutans 

    Species known only from SE Oregon:  Schinia lynda, Sympistis hathor 

    Species restricted to the Idaho, eastern Washington, and eastern Oregon:  Sympistis saxatilis, Sympistis sesmu

    Species found only in the Siskiyou Mountains:  Euros osticollis

  12. Which moths have the most records in our database? Back to top

    The following moth species are all represented by at least 250 different occurrence records in our database. The number next to each is the number of records in the database, to give you a sense of how commonly collected and/or photographed these species are.

    Malacosoma californicum - 780 records; Smerinthus ophthalmica - 768 records; Autographa californica  - 759 records; Panthea virginarius - 665 records; Lophocampa maculata - 634 records; Spilosoma virginica - 589 records; Apamea amputatrix - 581 records; Apamea devastator - 578 records; Phyllodesma americana - 545 records; Caenurgina erechtea - 523 records; Grammia ornata - 498 records; Acronicta dactylina - 497 records; Caradrina montana - 496 records; Leucania farcta - 494 records; Apamea cogitata - 488 records; Xestia c-nigrum - 437 records; Hyles lineata - 434 records; Malacosoma disstria - 432 records; Orthosia hibisci - 419 records; Habrosyne scripta - 412 records; Nadata gibbosa - 406 records; Hemaris thetis - 395 records; Raphia frater - 380 records; Idia americalis - 378 records; Spilosoma vagans - 366 records; Mythimna oxygala - 362 records; Xylomoia indirecta - 362 records; Acronicta grisea  - 360 records; Egira rubrica  - 357 records; Agrotis vancouverensis - 340 records; Dargida procinctus - 324 records; Oligocentria semirufescens - 324 records; Euxoa messoria - 320 records; Pyrrharctia isabella - 320 records; Furcula scolopendrina - 319 records; Tolype distincta - 318 records; Hypena californica - 318 records; Lacinipolia pensilis - 317 records; Pseudothyatira cymatophoroides - 313 records; Arctia caja - 313 records; Clostera apicalis - 313 records; Acronicta impressa - 312 records; Hemileuca eglanterina - 311 records; Schizura unicornis - 309 records; Egira crucialis - 304 records; Euxoa tessellata - 303 records; Drepana arcuata - 301 records; Antheraea polyphemus - 299 records; Hypena humuli - 299 records; Anarta trifolii - 295 records; Pheosia rimosa - 295 records; Grammia nevadensis - 292 records; Peridroma saucia - 289 records; Lacinipolia cuneata - 289 records; Feltia jaculifera - 288 records; Leucoma salicis - 285 records; Lacinipolia stricta - 281 records; Sphinx vashti - 279 records; Schizura ipomaeae - 274 records; Hyalophora euryalus - 272 records; Leptarctia californiae - 268 records; Oligia divesta - 266 records; Euxoa auxiliaris - 262 records; Autographa ampla - 262 records; Lophocampa argentata - 262 records; Drasteria adumbrata - 261 records; Diarsia rosaria - 259 records; Protodeltote albidula - 258 records; Gluphisia severa - 255 records; Zale lunata - 251 records; Parabagrotis sulinaris - 250 records; Cosmia praeacuta - 250 records