First, let's clear something up.

Scientific names are not Latin. You don't need to learn Latin to understand them. People who learn them don't do it so we can flaunt our knowledge of Latin. We would be laughed out of ancient Rome.

Imagine walking past the Colosseum in the year 100 A.D., dressed in your fly fishing garb, and trying to strike up a conversation.

You: "Hey, Brutus. How ya baetis? Ephemerella plecoptera ludens tricorythodes."

Brutus: "Huhae?"

You: "Paraleptophlebia! Cupida insecta, bicolor hemiptera siphloplecton perla stenonema."

Brutus looks at you funny.

You: "Yoloensis tipicus megaloptera obesa."

Brutus cuts your arms off with a sword.

You: "Isonychia."

What we use are mostly Latinized names. Latin has word endings out the wazoo, and it's handy to stick them onto the end of something else to make a new word nobody uses yet. Endings like -ium, -ella, -ptera, -idae, and -arcys come in handy. We can makium new wordsella so easiloptera from simplarcys Englishidae!

Sometimes the beginnings of names are borrowed from Latin, too, but many come from English names for the person who discovered the species or a part of its range. For example, the caddisfly Ceraclea wetzeli is named for the angling writer Charles Wetzel. And take a wild guess where you might find the stonefly Pteronarcys californica.

On the intimidation scale, these names are closer to Pig-Latin than to Linguistics 899.

Why Latin Names Are Useful

Intimidating or not, what's the point? Don't we already have names? What's wrong with calling a Sulphur a Sulphur? The problem is that, while sometimes a Sulphur is a Sulphur, other times a Sulphur is not a Sulphur, or at least not that Sulphur, or the other Sulphur, but yet another Sulphur, not to be confused with the Sulphur or the Sulphur. Confused? Me too.

Most common names refer to more than one species. Sulphur can mean Ephemerella invaria, Ephemerella dorothea, or Epeorus vitreus, at the very least.
Those names are a little harder to say, but there's just one name per critter and one critter per name.

"Still," you ask, "who cares if my Sulphur is Ephemerella invaria or Epeorus vitreus? Trout don't speak Latin!" That last accursed sentence is repeated ad nauseum in recent books, but few statements are both so obvious and so misleading.

Sure, trout don't understand Latin, but they do understand color and location and motion. There can be differences in all those things between insects with the same common name. The Sulphur Ephemerella invaria emerges from a pudgy olive or brown nymph that wiggles to the surface before the dun starts to pop out. The Sulphur Epeorus vitreus emerges near the bottom from a flat grayish nymph and floats to the surface as a bedraggled yellow dun.

Wouldn't that matter when you're fishing subsurface?

That's the key to the reason for learning Latin names: The bug you see and the bug the trout sees aren't always the same thing! Two insects which look nearly identical as adults may look nothing like each other underwater where the trout are eating them, and may behave in completely different ways.

Recognizing a species by its Latin name means associating it with the right hatching behavior and appearance of its important unseen stages. So the Latin name carries more practical information than the common name.

No-Nonsense Conversation

Nobody can solve all the riddles of our quirky hatches by himself, nor can the answers all be found in books. Instead we gain insights by swapping stream notes with each other, around the campfire or on websites like this one. But this study of the hatches is meaningless if we aren't using consistent and specific labels. Discussing hatch details by common name alone (without at least an implied understanding of the real species name) would be like trying to get my car fixed with a two-auto-part vocabulary:

Mechanic: "What seems to be the problem?"

Troutnut: "It's broken."

Mechanic: "Which part?"

Troutnut: "I don't know. The thingamajig doesn't work."

Mechanic: "Which thingamajig?"

Troutnut: "The one you use with the whatchamacallit to do the thing."

Mechanic: "You're gonna have to do better than that."

Troutnut: "What? Didn't you learn about thingamajigs in mechanic school?"

Mechanic: "Well, sir, there are a lot of thingamajigs in a car..."

Troutnut: "I don't need you to fix the other thingamajigs. Just the broken one."

Mechanic: "Which one is it?"

Troutnut: "The one with the whatchamacallit."

Mechanic hits me with a wrench.

When we don't have specific language, technical conversations just spin in circles. Read on to learn why "Blue-Winged Olives" are the fly fishing equivalents of "thingamajigs."