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Friday, July 25, 2014

Bugs - The Hydropsyche, "Spotted Sedge," Caddis

Bugs - The Hydropsyche Caddis

Each year I always look forward to summer and the hydropscyche caddis hatches. This bug is also commonly referred to as “the summer caddis” the “spotted sedge” or the “net spinning caddis”. On the Lower Sacramento River the bug takes on a brown or cinnamon cast. On the Lower Yuba River the bugs tend to have a green cast. The summer evenings will find active feeding fish willing to take caddis emergers and soft hackles. It is my favorite hatch of the year.

Ralph Cutter in his book “Fish Food” states that Hydropsychids are one of the most important of all insects for trout fishermen to know and understand. He also stated that despite this the Hydropsychids are one of the least understood and are poorly replicated. Almost no one fishes them correctly.

Hydrophsyche Facts

1. They are one of the few types of caddis that do not free roam in search for food.

2. The net-spinners build web retreats and let the food come to them.

3. They build funnel- shapped silken traps or span seines across gaps between rocks and sticks.

4. The uncased Hydropsyche is continuously exposed to trout, and ranges in size from 8-16 mm and can cycle through two or more generations in a fishing season.

5. Despite the fact the Hydropsyche builds a web retreat, it frequently strays and is commonly found roaming about streambed, draping strands of silk behind it in the cobbles. The silk not only works as a leash should the larva loose it’s footing, but it is also used by the caddis as a rappel line to lower itself across gaps between the rocks.

6. The larva are earth toned and difficult to see against the streambed background. By contrast the silk strands almost glow and are easily visiible from a distance. Trout have learned to key in to this luminescent line and frequently graze on the silk lines whether they have attached larva or not.
You can lighten the tippet for a foot or so above the larva imitation with a white grease pen, such as a Mean Streak marker.

7. When it comes time for pupation, the Hydropsyche entombs itself inside a dome of gravel. If you peel one of these cases off a rock, you’ll see that the bottom of the gravel dome is a sheet of silk through which you can view the evolving pupa.

8. With the exception of the Rhyacophilla, all other caddis pupa will be completely surrounded by sand and gravel.

Hydropsyche Habitat & Behavior

The preferred habitat of the Hydropsyche Caddis are riffles and runs. They often drift in the current, so where there are large populations, trout will feed on them year-round. A larva pattern dead-drifted near the bottom can be effective very effective in spring and fall, and even in winter.

Like all caddis, net-spinners pass through four stages of development: egg, larva, pupa, and adult. Most species require one year to develop from egg to adult. A few species pass through two generations in a single year.

In general, hatches are sparse in the spring. By June, activity increases. The heaviest activity often occurs in July and August.

Behavioral Drift

The larvae of net-spinning caddis periodically crawl out of their shelters, let go, and drift downstream 40, 50, or even 100 feet. This activity occurs on a daily cycle, and peaks near sunrise and sunset. Entomologists call this "behavioral drift" and speculate that it functions to disperse insect populations, thereby relieving competition and allowing the colonization of underutilized areas.

For the fishermen, it means increased food for trout, making nymph fishing during periods of peak drift very effective.

The Hydropsyche’s Life Line – A Gary LaFontaine Trick

Some hydropsyche caddis larvae throw a twist into normal drift behavior. Instead of simply letting go of the substrate, they attach a silk thread to the bottom and lower themselves downstream on a "life line." In his book Caddisflies, Gary LaFontaine discusses his increased success fishing with net-spinning caddis larva patterns when he colored the last 18 inches of his leader white to suggest this silk anchor line of the natural.

The Pupae

Once the larvae are mature, they seal themselves inside their shelter and transform into pupae. The pupae remain sealed inside until ready to emerge into adults. The complete development of the pupae typically requires four to six weeks.

When ready to emerge, the pupae swim to the surface, which is perhaps the most vulnerable period of the insect's life cycle. Trout feed selectively on the rising pupae, and imitating them is one of the most effective methods to use during a caddis hatch.

Peak emergence activity occurs in the late morning or early afternoon during the spring and fall. In mid-summer heavy hatches occur in the late afternoon and evening.

Hydropyshe Adults

Adult hydropsychids spend most of their time hiding on streamside vegetation. Mating occurs on the foliage, and unless a wind blows them over the water they are unavailable to fish.

Once egg laying begins, however, their vulnerability increases dramatically. Large swarms of gravid females congregate over the water from afternoon to late evening. To lay their eggs, they dive into the water and swim to the bottom, where they deposit strings of eggs on the substrate. Once egg laying is complete, they swim feebly back to the surface.

Such behavior makes them easy targets for feeding trout and an important stage for fly fishers to imitate. On streams like our Lower Yuba River, some of the fastest and most consistent fishing of the season occurs during the last hour of light when the hydropsychids lay their eggs.

Fishing Techniques

During a hatch, dead-drift a pupa pattern near the bottom in riffly water or just below riffles. An unweighted pupa pattern can also be drifted near the surface, or you can present a Soft Hackle with a wet-fly swing. Another good strategy is a dry fly with a pupa pattern as a dropper or trailer; the dry fly acts as an indicator and sometimes is taken by the trout.

After the hatch, errant and unlucky adults fall onto the water, and a dry fly is the right choice. Bankwater downwind or downstream from overhanging trees is a good place to cast your dry.

Females swim or crawl underwater to lay eggs. You can fish a dry at this time, or go subsurface with a Soft Hackle or Diving Caddis pattern.


Take some of these points to heart and you find out what a hammered take on a soft hackle is all about.

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Have any Questions or Comments? Let me know, Clay.