The Larger Moths Found in Washington State

FS296E

Sharon Collman, Extension Educator, Department of Entomology, Washington State University, Michael Bush, Ph.D. Extension Entomologist, Department of Entomology, Washington State University

Moths are stunningly beautiful and prevalent insects in Washington State and, through this publication, identifying them becomes much easier.

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Introduction

The insect order Lepidoptera includes moths and butterflies and is the most recognized group of insects in the world. Perhaps this popularity is due to the wide range of colorful wing patterns that adult moths and butterflies display. These wing patterns range from brightly to dull colored, single- or multicolored, simple to highly intricate designs, but all wings have one thing in common—microscopic scales of “color”. Thousands of microscopic scales cover the two pairs of wings that most moths and butterflies have, and these scales easily rub off like dust in your hand (Figure 1). The presence of scales is the key character that distinguishes the moths and butterflies from nearly all other insect orders, and certainly contributes to the beauty and popularity of Lepidoptera.

Figure 1. Moth scales under 100-fold magnification. Photo—M. Bush, WSU Extension.

One goal of this publication is to help Washington residents recognize all life stages of Lepidoptera and to distinguish adult moths from butterflies. There are over 1,200 species of moths in Washington State (Pacific Northwest Moths 2017). This publication seeks to help Washington residents recognize and appreciate the biggest and most spectacular moths native to our state.

Moths versus Butterflies

A general rule of thumb is that moths are active at dawn, dusk, and at night, while butterflies are active during the day. Thus, moths tend to be more subdued in coloration, while butterflies can be very bright and colorful. Not all moth colors follow these rules, as a few moths are not only bright and colorful, but active during the day. Moths tend to have thick and sturdy bodies covered with hair, while butterflies have thinner bodies.

Moth antennae are highly variable ranging from a slender thread to highly plumose (feathery) antennae, while butterflies have antennae that are threadlike with a knob at the furthest tip of the antennae. Finally, moths usually hold their wings tent-like over their back at rest (Figure 2), while butterflies hold their wings perpendicular when at rest (Figure 3).

Figure 2. Moths like this carpenter moth (*Prionoxystus robiniae*) tend to be more subdued in color, have thicker bodies, fold wings like a tent over their backs, and have variable shaped antennae (but never knobbed at the tip). Photo—M. Bush, WSU Extension.

Figure 3. Butterflies like this western tiger swallowtail, *Papilio rutulus*, tend to be brilliant in color, have thinner bodies, hold wings perpendicular over the body, and have thread-like antennae with knobs at the tip. Photo—M. Bush, WSU Extension.

Moth Life Cycle

All moths and butterflies go through complete metamorphosis, or a change in shape and size from egg to larva, larva to pupa, and finally from pupa to the adult stage.

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Introduction

Moths versus Butterflies

Moth Life Cycle

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