D251--1b9 baby bye3-2022.12.20-万思乐学V-learn

Alex

科普：为什么苍蝇喜欢搓脚?

因为，有些昆虫的感觉器官和人不一样。
人和大多数动物是用舌头来品尝味道的，味觉器官在舌头上。而苍蝇的味觉器官长在脚上，它是用脚来尝味道的。它发现任何食物都要“用脚先尝一尝”，再决定是否饱餐一顿。

苍蝇去的地方都很脏，脚上经常会沾上各种各样的杂物，如果不把这些杂物搓掉，就会使得脚上的味觉器官失灵。

有趣的是，苍蝇不饿的时候也会搓脚。这是因为脚上沾的东西多了，会增加它身体的重量，影响它的飞行速度。

为什么苍蝇吃那么多脏东西，却不会生病呢？因为它的消化系统“工作速度很快”，食物进入它的身体后，在非常短的时间内，有营养的物质被留下，废物和病菌被排出体外。大多数细菌在进入苍蝇的身体之后，还来不及繁殖就变成便便被拉出去了。 Foot print picture How to Identify Tracks 
The art of studying and identifying animal tracks is a practice that dates back to ancient times when humans relied on hunting and gathering for survival. The practice is used today by hunters, hobbyists, and professionals to monitor animal migration patterns, track endangered species, and better understand local wildlife. Tracks are found in a variety of places and identifying them is most easily done through a process of elimination. While the process can feel overwhelming at first, a little ingenuity, research, and interpretive skills are all you need to be on your way to easily identifying tracks in no time. 1、Spotting Mammal Tracks
Count the toes.
Note how many are on both the front and hind feet. Felines猫科, canines犬科, and rabbits all have 4 toes, while smaller animals like mice have 4 toes on the front foot and 5 on the hind. Knowing the basics about toes can help you eliminate 消除many wrong possibilities right away.[2]
Observe the shape of the toes and note if they are long or rounded.
Always check other tracks in the same area to confirm your findings. It’s common to get an animal's hind foot mixed-up with its front foot, so studying the other tracks will help you verify what you’re seeing.[3] Look for claws.
If you can see claws in the track, take note of the size and shape. Some are large and blunt while others are thin and sharp. Noting the claw size will help in the process of elimination.[4]
Animals that climb tend to have small claws and animals that dig have large blunt ones.[5] Check if the track is symmetrical[sɪ'metrɪkl]对称的
Picture a line down the center of the track and compare the right and left sides. Typically, hooves are very symmetrical while other types of tracks are not.[6]
For instance, bears have huge, asymmetrical tracks with 5 toes. The front tracks are smaller than the hind tracks. Identify canine [ˈkenaɪn] n.犬(齿);犬科动物 tracks by their oval shape and 4 toe prints.
Canine tracks also point forward, have a concave heel pad, and visible claws. The front paws are larger than the hind paws.[7]
Wolves have the largest canine tracks at 4 inches (10 cm) long.
Coyote prints are smaller and narrower—about 2.5–3 inches (6.4–7.6 cm).
Fox prints are fuzzier due to the hair in the paws and measure around 2–3 inches (5.1–7.6 cm).
Domestic dog prints are similar in size and shape to wolf and coyote tracks. However, dog prints will zig-zag more than wild animal prints, which tend to follow a straight line. Recognize feline [ˈfilaɪn] n.猫科动物tracks by their rounded “M” shape.
The 3-lobed heel pads on felines look similar to a bubble letter “M.” Feline tracks have 4 toes and are about as wide as they are long. Typically, you won’t see claws on feline tracks.[8]
Mountain lion (or cougar) tracks are the largest feline tracks, measuring at about 3 inches (7.6 cm) long and wide.
Lynx tracks look very similar to mountain lion tracks and are about the same size. However, they are less defined because of the fur around the paws of a lynx.
Bobcat tracks look similar to that of a coyote or fox, but are rounder and lack claw marks. They are about 2 inches (5.1 cm) long and wide.
House cat prints are pretty small—1–1.5 inches (2.5–3.8 cm)—and generally don’t follow the straight paths that wild animals do. Identify small mammals by their 5-toed prints.
Many of the smaller mammals, with the exception of rabbits, have 5 toes. They range in size from 1–4 inches (2.5–10.2 cm).[9]
Some people think raccoon prints look like baby hands, so if you see a track that looks human-like, it could belong to a raccoon. Both prints have 5 toes, but the front ones are smaller than the back ones.
Opossum tracks are quite similar to raccoon tracks. However, the tracks of their hind feet clearly show their opposable thumbs.
Otter tracks are wider and are most often found on muddy river banks. Otters have partially webbed feet and short claws.
The front and hind feet of a skunk are the same size, unlike many other mammals. They have 5 toes and visible claws.
Rabbits stagger their feet, leading to Y-shaped tracks. Unlike the other animals in this group, rabbits do not have 5 toes. Spot hoof [huf] 蹄 tracks by their distinct 2-toed shape.
Hooves are generally symmetrical. Depending on the animal, the tracks may be round, heart-shaped, or square.
Moose have the largest prints at 5–7 inches (13–18 cm). They are heart-shaped, deep, and sometimes show claw marks.
Bison美洲或欧洲野牛 have round prints that are wider than other animals. Typically, they’re 4.5–6 inches (11–15 cm) long.
Elk 麋鹿tracks look similar to moose tracks but are smaller—about 3–5 inches (7.6–12.7 cm). They also have rounder toes that are not as tapered at the tips.
Deer tracks show 2 distinct toes and a small dot shape underneath each toe. They’re slightly angled away from each other and measure about 2–3.5 inches (5.1–8.9 cm).
Bighorn sheep加拿大盘羊 tracks look like deer tracks but are smaller and less pointed. They have a blockier shape and straighter edges.
Wild boar 野猪tracks also look similar to deer tracks. They’re about the same size but have rounder, wider toes. The dew claw is also present in their prints.
Mountain goat tracks are V-shaped and much smaller than hooved animals like elk or deer. Recognize that rodent[ˈrodnt] n.啮齿类动物prints have 4 toes in the front and 5 in the back.
Each rodent has a distinct清楚的 track, and the one thing they have in common is the number of toes on each foot.[10]
Beavers have webbed feet. Look for beaver tracks near rivers. The tracks from their back feet often cover up their front feet, and their tail can remove any trace of either!
Porcupine[ˈpɔrkjəˌpaɪn] n.豪猪prints often show only the pads of their feet and they are pigeon-toed, so the tracks point inward. Sometimes, you can see an impression of their tail along with their prints.
Mice have bigger back feet than front feet. Their tracks show 4 tiny feet and sometimes a tail drag.
Squirrel tracks also show 4 prints. Their back feet are around 0.5–1.0 inch (1.3–2.5 cm) and their front feet are 0.25–0.50 inches (0.64–1.27 cm). Squirrels tend to hop and move from tree to tree. 2、Identifying Bird Tracks
Take note of the habitat where the tracks are found.
Birds tend to live in specific habitats depending on their particular needs. Ducks will often be found near water, perching飞落 birds generally stay near wooded areas, and gaming birds like open spaces. Study the area around the bird tracks to help narrow down the possibilities.[11]
Since bird tracks look so similar, the best way to figure out which bird the prints belong to is to assess the habitat and find out which species frequent the area. See if the tracks alternate or are in pairs.
Birds that live primarily on the ground, like turkeys, have alternating tracks. Conversely, tree-dwelling birds, including crows, leave pairs of prints because they hop on the ground.[12] Identify classic tracks by their Y-shape.
Classic tracks (also known as anisodactyl) have 3 toes pointing forward and 1 long toe pointing backward. The most common birds in this category are doves, ravens, egrets, hawks, crows, grouse, and perching birds.[13] Recognize webbed tracks by their wide shape.
Webbed (or palmate) tracks have forward facing toes that are webbed and outer toes that curve slightly inward. The most common birds in this category are ducks, geese, and gulls.[15] Identify zygodactyl tracks by their 4 toes.
Zygodactyl n.攀木类之鸟;对趾鸟tracks have 2 toes that point forward and 2 that point backward. A slightly less common track, these belong to roadrunners, cuckoos [ˈku:ku:z] n. 布谷鸟, owls, and woodpeckers.[16] 3、Identifying Reptile and Amphibian Tracks
Note the size of the tracks.
While lizards typically leave behind the same type of track, size can vary significantly depending on the specific species. Measuring the length and width then reference various lizard sizes if you believe you’ve found reptile tracks. Determine if the tracks are inland or near water.
Depending on the type of reptile, understanding the location of the track will help you make determinations. Some reptiles like iguanas prefer dry areas and others like alligators will usually be found near water.
Spot alligator tracks by their 5 toes.
Alligator tracks are rarely mistaken for any other tracks—you can see 5 toes in the front tracks and 4 in the hind tracks. They will also have a scaled appearance. These tracks are much larger than those of most other reptiles.[17]
The tail of the alligator leaves a large trough between its prints.
Recognize lizard and salamander 蜥蜴tracks from their tail drags.
Lizard and salamander tracks are generally identified more easily from their tail drags than footprints. Their tails leave distinct lines and will often be accompanied with blurry foot marks on each side.[18]
Salamander tail tracks move from side to side while lizard tail tracks are much straighter. Note that snake tracks look like smudges污迹.
Since snakes don’t have feet, they don’t leave tracks in the way that other animals do. You may see slight smudges or continual S-shaped prints in the sand or dirt.[19] Identify turtle tracks by their continuous line.
Turtles take steps that are very close together, resulting in a continuous line of tracks on each side of their body. They look sort of like tank treads and have large claw marks and 5 toes on both feet. [20]
Sometimes, only 4 toes are visible in the hind prints. Spot frog and toad tracks by their “K” shape.
Both animals have 4 toes in the front and 5 in the back. Often, the front feet land between the back feet. Sometimes, you’ll be able to see the frog or toad’s belly impression in the tracks as well.[21]