Scientists sometimes use the word "crepuscular" to describe nocturnal animals that are not active when it is very dark at night; they are mostly active near dawn, dusk, and sometimes when the moon makes a lot of light.
Skipper (butterfly)
The skippers are a family of butterflies, the Hesperiidae. They are named after their quick, darting flight.
Skippers used to be classified in their own superfamily, Hesperioidea, because they have their antennae clubs hooked backward like a crochet while the other butterflies have club-like tips to their antennae. Skippers also have generally stockier bodies than regular butterflies, with stronger wing muscles.
There are about 3500 species of skippers. They are usually classified in the following subfamilies:
Many species of skippers look frustratingly alike. For example, some species in the genera "Erynnis", "Hesperia", and "Amblyscirtes" cannot currently be distinguished in the field even by experts. The only reliable method of telling them apart involving dissection and examination of the genitalia.
Examples include:
Energy conservation
Energy conservation is reducing the amount of energy used for different purposes. This may result in an increase of financial capital, environmental value, national and personal security, and human comfort.
Individuals and organizations that consume energy may conserve energy to reduce costs and promote economic, political and environmental sustainability. Industrial and commercial users may want to increase efficiency and thus maximize profit.
On a larger scale, energy conservation is an energy policy. In general, energy conservation reduces the energy consumption and energy demand per capita. This reduces the rise in energy costs, and can reduce the need for new power plants, and energy imports. The reduced energy demand can provide more flexibility in choosing the methods of energy production.
By reducing emissions, energy conservation helps to prevent climate change. Energy conservation makes it easier to replace non-renewable resources with renewable energy. Energy conservation is often the most economical solution to energy shortages.
The U.S. is the largest consumer of energy, although at current levels of growth, China may become the leading energy consumer. The U.S. Department of Energy categorizes national energy use in four broad sectors: transportation, residential, commercial, and industrial.
Energy usage in the transportation and residential sectors (about half of U.S. energy consumption) is largely controlled by individual domestic consumers. Commercial and industrial energy usage are controlled by businesses. National energy policy has a significant effect on energy usage across all four sectors.
The transportation sector includes all vehicles used for personal or freight transportation. Of the energy used in this sector, about 65% is used by gasoline-powered vehicles, mostly personally owned. Diesel-powered transport (trains, merchant ships, heavy trucks, etc.) consumes about 20%, and air traffic consumes most of the remaining 15%.
The oil supply crises of the 1970s spurred the creation, in 1975, of the federal Corporate Average Fuel Economy (CAFE) program, which required auto manufacturers to meet progressively higher fleet fuel economy targets. The next decade saw dramatic improvements in fuel economy, mostly the result of reductions in vehicle size and weight. These gains eroded somewhat after 1990 due to the growing popularity of sport utility vehicles, pickup trucks and minivans, which fall under the more lenient "light truck" CAFE standard.
In addition to the CAFE program, the U.S. government has tried to encourage better vehicle efficiency through tax policy. Since 2002, taxpayers have been eligible for income tax credits for gas/electric hybrid vehicles. A "gas-guzzler" tax has been assessed on manufacturers since 1978 for cars with exceptionally poor fuel economy. While this tax remains in effect, it currently generates very little revenue as overall fuel economy has improved.
Another focus in gasoline conservation is reducing the number of miles driven. An estimated 40% of American automobile use is associated with daily commuting. Many urban areas offer subsidized public transportation to reduce commuting traffic, and encourage carpooling by providing designated high-occupancy vehicle lanes and lower tolls for cars with multiple riders. In recent years telecommuting has also become a viable alternative to commuting for some jobs.
A vehicle's gas mileage normally decreases rapidly at speeds above 55 miles per hour. A car or truck moving at 55 miles an hour can get about 15 percent better fuel economy than the same car going 65 mph. According to the U.S. Department of Energy (DOE), as a rule of thumb, each 5 mph you drive over 60 mph is similar to paying an additional $1.20 per gallon for gas (at $3.10 per gallon).
The residential sector refers to all private residences, including single-family homes, apartments, manufactured homes and dormitories. Energy use in this sector varies significantly across the country, due to regional climate differences and different regulation. On average, about half of the energy used in the U.S. homes is expended on space conditioning (i.e. heating and cooling).
The efficiency of furnaces and air conditioners has increased steadily since the energy crises of the 1970s. The 1987 National Appliance Energy Conservation Act authorized the Department of Energy to set minimum efficiency standards for space conditioning equipment and other appliances each year, based on what is "technologically feasible and economically justified".
Despite technological improvements, many American lifestyle changes have put higher demands on heating and cooling resources. The average size of homes built in the United States has increased significantly, from 1500 ft² in 1970 to 2300 ft² in 2005. The single-person household has become more common, as has central air conditioning: 23% of households had central air conditioning in 1978, that figure rose to 55% by 2001.
As a cheaper alternative to the purchase of a new furnace or air conditioner, most public utilities encourage smaller changes the consumer can make. Consumers have also been asked to adopt a wider indoor temperature range (e.g. 65 °F in the winter, 80 °F in the summer).
Energy usage in some homes may vary widely from these averages. In most residences no single appliance dominates, and any conservation efforts must be directed to numerous areas in order to achieve substantial energy savings. However, ground source heat pump systems are the more energy efficient, environmentally clean, and cost-effective space conditioning systems available (Environmental Protection Agency). They can achieve reductions in energy consumptions of up to 70%.
Current best practices in building design and construction result in homes that are much more energy conserving than average new homes. See Passive house, Superinsulation, Self-sufficient homes, Zero energy building, Earthship, Straw-bale construction, MIT Design Advisor, Energy Conservation Code for Indian Commercial Buildings.
Smart ways to construct homes such that minimal resources are used to cooling and heating the house in summer and winter respectively can significantly reduce energy costs!