Here are some photos of Josh Esposito doing mosquito control in the backcountry near Bear Valley. The vernal pools can sometimes hold tens of thousands of mosquito larvae. Cattle are trucked up for spring and summer grazing, and provide unlimited blood for the snow pool mosquitoes. But years of treating have cut the mosquito numbers way down. (Note that we have not seen any negative impact on the frog population.)
The area around Columbia State Park was hydraulically mined during the gold rush, and many dug-out areas remain. These fill with water during the winter, becoming vernal pools. Floodwater mosquitoes like these pools.
Here are photos and videos showing how infested these pools can become. Included below is a compilation of mosquitoes suffocating videos, after a treatment with the BVA 2 oil.
11 May 2017.
For a number of years, the area around the homes located at the upper end of Apple Valley Drive, Sonora, California, have had extraordinary numbers of large, floodwater mosquitoes, genus Aedes (or Ochlerotatus), in the spring. These mosquitoes are larger than the western treehole mosquitoes that are common in the foothills at that time of year. The source of the floodwater mosquitoes has been a mystery, as searching in late spring did not reveal a source. We did a search in mid-April 2017, and found a major breeding area.
Hiking behind the creek, and towards Summer’s Pond, revealed a number of possibilities. Sampling yielded no mosquitoes, except in one location, at what appeared to be a small vernal pool on the edge of thick vegetation (1st photo below). About 100 feet away was what appeared to a second, small vernal pool (2nd photo below). The density of the brush and trees was so great that visibility was highly limited, and these pools did not appear connected. Further investigation revealed that the vegetation was concealing what was actually a gigantic vernal pool, about a quarter of an acre, its perimeter, and center as well, overgrown with thick vegetation. This cryptic, huge pool, hiding in plain sight, contained thousands of mosquito larvae.
The location of the pool is not discernable in the Google Earth 2016 satellite image (38°00’16.49″ N 120°19’32.67″ W), below, but is readily visible in the 1993 image, prior to the tree and shrub growth.
As we do elsewhere, we monitored the frogs, before and after treatment with the mosquito larvicidal oil, and found that the frog population was unaffected.
In addition, we explored a second potential mosquito breeding site, shown in the 1993 satellite image below, by the oval. Sampling on 23 April 2017 did not yield any mosquito larvae, but a number of the larger, floodwater mosquitoes were in the brush area, attempting to bite. This area appears to be directly linked to Summer’s Pond, and is also heavily overgrown. See the images below.
Photos taken on 31 May 2016. Click to enlarge.
Mosquito Lake, in Alpine County, is located a few miles east of Lake Alpine and Bear Valley. You might think, based on the name, that the mosquitoes are breeding in the lake. No, the mosquitoes come from vernal pools, or snow-melt pools, near the lake. These photos were taken 31 May 2016.
Click on an image to enlarge it.
These photos were taken May 24, 2016, at Bear Valley, near Blood’s Meadow.
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(Note:click on an image to enlarge it)
Some snow melt pools, or vernal pools, can contain tens of thousands of mosquito larvae. These photos and videos were taken on 30 March 2015, Alpine County. “T-pool” is named for being the top of a “T’, coming up from ‘Fairy Shrimp Pool’ (see below).
Fairy Shrimp Pool
Views of Fairy Shrimp Pond, from both ends. This vernal pool is home to a species of fairy shrimp, as well as a lot of snow pool mosquitoes.
The fairy shrimp species is probably Streptocephalus sealii, as it matches the description and distribution. This distribution map is from Fairy Shrimps Of California’s Puddles, Pools, And Playas by Clyde H. Eriksen and Denton Belk, 1999.
This vernal pool contains surprisingly few mosquito larvae, despite its large size, and this rarity of mosquitoes occurs year to year.
Bloods Meadow Pool
Bloods Meadow is home to a very large vernal pool in early spring. We find mosquito larvae all around its fringes, and in various locations within the meadow itself.
Sierran Treefrog – Pseudacris sierra is common near Bloods Meadow pool.