Frequently Asked Questions
- What is the life cycle of a moth?
- What are the differences between moths and butterflies?
- Are all moths nocturnal?
- Do all moths spin cocoons?
- What is the largest moth in the Pacific Northwest?
- How long do moths live?
- What are the worst pest moths in the region?
- What do caterpillars and moths eat?
- What roles do moths play in the environment?
- Are there any threatened or endangered moths in the Pacific Northwest?
- Which moths are endemic to (only found in) the Pacific Northwest?
- Which moths have the most records in our database?
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.
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!
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.
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!
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!
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.
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).
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.
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.
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.
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 that are limited to western Washington and western Oregon: Ceranemota crumbi
Species found only the northern mountains of the Pacific Northwest: Euchalcia borealis
Species found only in the Siskiyou Mountains: Euros osticollis
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.
- 360 records; - 357 records; - 340 records; - 324 records; - 324 records; - 320 records; - 320 records; - 319 records; - 318 records; - 318 records; - 317 records; - 313 records; - 313 records; - 313 records; - 312 records; - 311 records; - 309 records; - 304 records; - 303 records; - 301 records; - 299 records; - 299 records; - 295 records; - 295 records; - 292 records; - 289 records; - 289 records; - 288 records; - 285 records; - 281 records; - 279 records; - 274 records; - 272 records; - 268 records; - 266 records; - 262 records; - 262 records; - 262 records; - 261 records; - 259 records; - 258 records; - 255 records; - 251 records; - 250 records; - 250 records- 780 records; - 768 records; - 759 records; - 665 records; - 634 records; - 589 records; - 581 records; - 578 records; - 545 records; - 523 records; - 498 records; - 497 records; - 496 records; - 494 records; - 488 records; - 437 records; - 434 records; - 432 records; - 419 records; - 412 records; - 406 records; - 395 records; - 380 records; - 378 records; - 366 records; - 362 records; - 362 records;