biology

Xerces blue

Xerces blue is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Xerces blue rather than just read about it. In short: The Xerces blue (Glaucopsyche xerces) is an extinct species of butterfly in the gossamer-winged butterfly family, Lycaenidae. The species lived in coastal sand dunes of the Sunset District of the San Francisco Peninsula in California.

Key takeaways

Xerces blue belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Xerces blue to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Xerces blue from memory before moving on to harder problems.

Reference excerpt

The Xerces blue (Glaucopsyche xerces) is an extinct species of butterfly in the gossamer-winged butterfly family, Lycaenidae. The species lived in coastal sand dunes of the Sunset District of the San Francisco Peninsula in California. The Xerces blue is believed to be the first American butterfly species to become extinct due to loss of habitat caused by urban development. The last Xerces blue was seen in 1941 or 1943 on land that is now part of the Golden Gate National Recreation Area.

Taxonomy Genetic analysis of museum specimens published in 2021 confirmed that the Xerces blue represented a distinct species within the genus Glaucopsyche, with its closest relatives being Glaucopsyche australis and Glaucopsyche pseudoxerces, with this group most closely related to Glaucopsyche lygdamus (the silvery blue).

Extinction and ecology The species was first described and documented in 1852. It was characterized by blue wings with white spots. The butterflies fed on vegetation belonging to the genus Lotus and Lupinus. The loss of the Lotus plant that the butterfly fed on while in its larval stages is believed to be one reason for the extinction of the Xerces blue. The plant could not survive in the disturbed soils due to human development and was no longer available to the Xerces blue. Lupinus, the Xerces blue's other vegetative food source, was not suitable for the larval stages. Preserved specimens are found in California Academy of Sciences, Bohart Museum, and the Harvard Museum of Natural History.

Reestablishment efforts Efforts are ongoing to reestablish related butterflies in the Xerces blue's former habitat. The Palos Verdes blue (Glaucopsyche lygdamus palosverdesensis), which is considered a Los Angeles cousin of the Xerces, is being reared in labs. A new Xerces-like subspecies of the silvery blue (Glaucopsyche lygdamus), which the Xerces blue was thought to be a subspecies of has been discovered as well, and has been analyzed as a potential way to revive the Xerces blue. Successful reintroduction efforts of the silvery blue occurred in 2024 in a collaboration between the Presidio Land Trust, National Park Service, and California Academy of Sciences, among other groups. In 2025, silvery blue offspring were documented in the Lobos Creek Valley Dunes, implying successful reproduction within the Presidio. Releases of silvery blues have continued in 2025.

References

External links Xerces.org – An invertebrate conservation society BUTTERFLIES of CALIFORNIA - Book by J. A. Comstock with chapters on the Xerces Blue w/ illustrations

Illustrations

Worked examples

Example 1 — a first encounter with Xerces blue

Start with the simplest possible case. Write down what Xerces blue claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Xerces blue before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Xerces blue ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Xerces blue

In research: Xerces blue appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Xerces blue in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Xerces blue is common in secondary-school and first-year university syllabi. It links to neighbouring topics Butterflies described in 1852, Extinct animals of the United States, Extinct butterflies, so understanding it makes those chapters shorter.
In everyday life: Look for Xerces blue outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Xerces blue in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Xerces blue means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Xerces blue out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Xerces blue in simple terms?

Why does Xerces blue matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Xerces blue?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Xerces blue.