My Science School

Technically speaking, spiders are not insects! Why aren’t they exactly? We’ll look into a few main reasons why spiders and insects are so different. But first, let’s break down what spiders and insects have in common, which is actually quite a bit.

To understand the similarities and differences between spiders and insects, we have to cover a bit of taxonomy. Taxonomy is the science of classifying all living things. Spiders, insects, fish, birds, and humans all fall into the Kingdom Animalia. Pretty much every animal is able to breathe and move, unlike plants and fungi. Additionally, animals are multicellular, unlike bacteria. Let’s dive deeper into the world of taxonomy and discover more about the classification of spiders and insects.

The next taxonomic level down is where spiders and insects lose their similarities. Spiders are in a class of animals known as arachnids. Spiders, scorpions, mites, and ticks are all different kinds of arachnids. Perhaps the biggest difference between arachnids and insects are the number of legs they have. One of the defining characteristics of spiders and other arachnids is that they have 8 legs. Insects, on the other hand, only have 6. This difference may not seem that significant, but it’s one of the most important things that separate these two classes of animals!

Next up is the number of body segments. Spiders have two segments – the abdomen, and the cephalothorax (which is a combination of a head and thorax). Insects boast three distinct segments – an abdomen, a thorax, and a head. Although they serve essentially the same functions, the body segments are another characteristic that spiders and insects do not have in common.

 

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Are you thinking of these insects being particularly chatty? Well, you may not be off the mark. Yes, gregarious locusts are sociable. But they also exhibit a few other characteristics when they are gregarious. Let's find out more about this.

What are locusts?

Locusts are insects that belong to the grasshopper family, and so, look a lot like grasshoppers. But there are a few crucial differences between them. Among those is the ability of locusts to fly long distances and also invade fields as swans, causing unimaginable damage to agricultural crops. Remember locust invasion in several parts of Africa and India in 2020, reported widely the media? However, locusts are solitary creatures just like grasshoppers, and they come together as swarms only when they are gregarious. Gregarious is a phase that occurs during a locust's lifecycle.

When do they become gregarious?

During the dry season when there's not much vegetation around, locusts are forced to come together on small patches of land that has a little vegetation, When that happens, the chemical serotonin gets released in their body. With this they reach the gregarious phase, during which they are sociable. According to National Geographic "Locusts can even change color and body shape when they move into this phase. Their endurance increases and even their brains get larger.” Soon, when it rains, they multiply in large numbers, the place becomes even more crowded, and they start invading agricultural lands in swarms. Reports suggest that the phase is triggered by the need for food.

There are several varieties of locusts that take over large areas of agricultural lands. However, the desert locust is the most dreaded for its country crossing abilities and for polishing off tens of thousands of acres of vegetation.

 

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The word spider invariably evokes visuals of stunningly beautiful and intricate webs. But do you know not all spiders spin webs? Yes, you read that right. There are a few varieties that do not spin webs at all. However, what is interesting is that all spiders produce silk. Which means their silk has several uses other than just spinning the web. This silk a strong, flexible protein fibre - is used as a tether for safety in case of a fall; to create egg sacs: to wrap up prey: to make nests, etc.

Spiders have structures called spinnerets on their abdomen: these are their silk-spinning organs. Most of them have a cluster of spinnerets, though the exact number differs with species. The silk is a liquid before it comes out. While the fact that it has many uses is fascinating, what is intriguing about spider silk is its strength. Most of them are said to be five times stronger than steel. And a study in 2018 revealed how the silk gets its strength. When scientists analysed the silk of a specific species of spider using an atomic force microscope, they discovered that "each strand - which is 1000 times thinner than a human hair is actually made up of thousands of nanostrands”!

Trivia

There are several varieties of spider webs because different species use different patterns to construct their webs. Apparently, the webs can be categorised into orb, sheet tangle, funnel, lace, radial, and purse, based on their structure, and the webs also give a general idea about the family a spider could belong to.

 

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Mosquitoes shouldn’t be able to fly in the rain, but they still do!

Despite being roughly the same size, a single raindrop can weigh up to 50 times more than an average mosquito. So, a mosquito flying in the rain is like a person wandering about when it’s raining buses! Common sense says mosquitoes shouldn’t survive the rain, but they are a stubborn bunch.

So how do they survive the rain?

Well firstly, they do not get wet. The glassy wings and the tiny hairs on their bodies are designed to repel water. So, when a raindrop bounces off of a mosquito, one of the two scenarios may occur:

Raindrop hits wings or legs [very probable]

Raindrop hits the core body or head [unlikely]

In the first scenario, the mosquito rotates around the raindrop due to its hydrophobic body and regains normal flight with minimal effort. In other terms, the mosquitoes just shake it off

In the second scenario, the mosquito gets hit hard and drops in altitude. But it still manages to survive by taking on only a fraction of the full momentum [2–17% depending on the mosquito] of the raindrop upon impact. It does this by making the collision inelastic. The secret to this is to go with the flow

Besides, the drastic difference in mass between the mosquito and the raindrop actually becomes an advantage when we analyse the system by applying the law of conservation of momentum.

And that is how the pesky little mosquitoes fly in the rain.

 

Credit : Quora

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Pitcher plants usually conjure up visuals of unsuspecting insects falling into a watery grave. But did you know these insectivorous plants also offer a fascinating story on a mutually beneficial relationship in the wild?

A place for roosting

One variety of pitcher plant that grows on trees in Brunie’s Borneo gladly welcomes a type of woolly bat to safely roost in its pitchers. And how is this mutually beneficial? Because, the bat droppings provide the pitcher plant much-needed nutrients. Since this plant dwells on trees, its chances of trapping insects are said to be lower than those of its cousins that grow on the ground. A study indicated that as the bats roost in the safety of the pitchers, the plants get about a third of their nutrients in the form of nitrogen from bat droppings. Of course, it certainly helps that this variety of plant has large pitchers, less digestive liquid, and more importantly, some sort of a “girdle” mid-way that prevents the bat from slipping and falling into the fluid. Interestingly, these bats use only this specific variety of plants for roosting. A subsequent study revealed that the back wall of the pitcher “strongly reflects incoming ultrasound in the direction it come from, and over a large area”, helping the bat locate these plants from far.

Not just bats

There are a few other pitcher plant species too that welcome such small mammals. For instance, one variety of plant tempts tree shrews with nutritious nectar on the pitcher’s lid. But there’s a catch. The shrews will be able to lick the nectar only when “they position their backsides over the mouth of the pitcher”. The pitcher plant offers nectar and, in return, expects nutrient-rich shrew dropping! Occasionally though, a shrew falls to its death in the pitcher fluid.

 

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Not just flies, spiders, lizards, ants and other creatures too have the unique ability to walk up the wall. They are not defying gravity, of course. They simply have specialised feet that enable them to hold on to the wall without falling off. They use a combination of features such as tiny hairs, natural adhesives and large claws to carry out the task.

In the case of flies, each foot has two fat footpads that give the insect plenty of surface area that aid in climbing. The footpads are covered with adhesives produced by the insect itself. These pads, called pulvilli, come equipped with tiny bristles or hairs that have spatula-like tips. These hairs are called setae. Flies need sticky feet to walk on ceilings, but not so sticky that they get stuck upside down. So each foot also comes with a pair of claw-like structures that help remove the gooey foot off the wall. If you look closely, you will notice that most wall-climbing creatures leave behind sticky footprints. The ‘claws’ and adhesions also help the insect hold on to different types of surfaces – walls, wood or glasses.

 

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Scientists are not sure. Mosquitoes are not known for eating waste. They don’t improve the soil like earthworms do. Yes, frogs prey on mosquitoes, but it is not their major food source. Mosquitoes pollinate plants since the males drink nectar, but they don’t do a lot of it.

Winegard thinks that may be mosquitoes have evolved to check the uncontrolled human population growth. But no one will accept that theory. Others say they have been put on earth to tell us that we are not as mighty as we think we are. We can be brought down by a tiny insect army. Do you agree?

So do we eradicate all mosquitoes? Biologists say they are part of the ecological cycle, so we cannot. They are there for a purpose, for balance in the eco-system. Who knows, maybe if we kill off all the mosquitoes, we may upset this balance and the natural selection of species. Winegard also points out: “Since there are 3,500 mosquito species and very few transmit diseases, perhaps the eradication of those that transmit diseases is extreme.”

 

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Why mosquitoes bite and what to do:

• According to studies, mosquitoes prefer blood type O over A, B or a mix of any of them. So if your blood type is O, you find more of the insects buzzing around you.


• Mosquitoes are attracted to bright colours.


• Mosquitoes like the smell of beer in beer drinkers.


• When you exercise, you let out a lot of carbon dioxide. Mosquitoes thrive on CO2.


• Our skin usually keeps us safe from mosquitoes, but you know they attack your legs. That is because of the bacteria on your feet.


• All this information about what is good for them is genetically coded into the mosquito brain. So the insect knows where to find food.

What you can do:

• Sleep under a net if your area is mosquito-prone.


• Keep surroundings clean to prevent them from breeding.


• Keep your feet covered in places like the park, bus stands, railway stations, movie halls.


• Wash your feet well when you reach home after school, before sitting down at the table to study.

 

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Mosquitoes buzzed around even when dinosaurs roamed the earth. By sucking blood and carrying parasites of crippling diseases, these creatures have ravaged human populations, especially in Africa. Mosquito bites have caused the death and disability of millions of people, ruining the economy of some countries:

Weaponized

Mosquitoes have been used as a biological weapon during wars. According to Winegard, the Nazis purposely re-flooded the Pontine Marshes around Rome and Naples in Italy to reintroduce mosquitoes, and they spread malaria in that part of Italy during World War II. The soldiers fighting the Nazis got malaria and had to be sent back.

With all the science and technology we have now, why are we not eradicating mosquitoes?

Here is why:

They’re everywhere

Mosquitoes are everywhere – in swamps, forests, fields and homes – 110 trillion of them. They are global, and have been around for 100 million years. They are great survivors, “masters of evolutionary adaptation.” They are resilient, which means they can adapt to different weather conditions and terrains. They withstood “global showers” of DDT spray, and five types of mosquitoes are now immune to this pesticide. We all have defences in our body against disease. In the same way, mosquitoes have developed immunity to survive our attempts to kill them off.

Untiring work

Still, a lot of work has been done to tackle this relentless insect. Funding is available for research on mosquito-borne disease. Mosquito nets are given out in large numbers to people. Insecticides and malaria drugs are distributed in counties that cannot afford them. Doctors say death from malaria, the major disease caused by mosquitoes, has decreased across the world. However, there is an increase in the incidence of Zika, West Nile, and dengue.

Governments are low trying biological control of mosquitoes. This is to avoid use of pesticides. In this method, fish are bred in ponds where mosquitoes lay eggs. The fish eat the larvae. There are also plants that kill mosquito larvae. But these have had only limited success in keeping down mosquito numbers.

Climate crisis

Mosquitoes thrive when we create the right environment for them – by rearing animals and plants close to our homes, cutting down trees, letting water stagnate and keeping sewage channels open. Climate change, which is now a serious crisis, also helps breed mosquitoes. “Increased temperatures mean a longer breeding season for mosquitoes,” said Winegard in an interview.

“Canada has seen a 10% increase in mosquito-borne disease in the last 20 years. In the southern US, we’ve seen domestic cases of Zika, chikungunya, and even dengue in the last 10 years. So if temperatures rise around the planet, which increases the risk of spreading disease.”

 

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The mosquito transmits or carries more diseases than any other insect. The six major ones spread by it are: malaria, dengue fever, chikungunya, zika fever, lymphatic filariasis and Japanese encephalitis.

Different species of the mosquito cause different illnesses. Research into human civilisation shows that mosquito-borne diseases throughout history have killed more people than man-made weapons.

In the book: The Mosquito: A Human History of Our Deadliest Predator, historian Timothy Winegard gives us this startling fact: over the course of 200,000 years, 108 billion people have lived on Earth. Of these, 52 billion have been killed by mosquitoes. Since 2000, an average of 2 million people have died due to diseases caused by mosquitoes. And so, it is safe to sat, the insect has had a disastrous effect on our civilisation.

 

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Ants are some of the most skilful architects of the animal world, building a vast network of chambers under the ground. They have no blueprint to speak of, and no visible leader! They also work in total darkness.

An ant expert, Walter Tschinkel, made casts of ant colonies by pouring plaster, wax or molten metal into the hollows. He observed that most chambers were close to the surface, with smaller, more spaced-out rooms farther away. How ants gauge depth is not known, but Tschinkel thinks they can sense the carbon dioxide content of the soil. The amount of carbon dioxide increases as one goes deeper underground.

 

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It might sound like something out of a horror story, but the aptly-named bone-house wasp builds its nest out of dead ants! It stuffs the ant bodies between the mud walls of its nest. Scientists discovered that the corpses not only provided insulation from heat and cold that the scent kept away a number of predators. Most animals avoid ant colonies because they are known to put up a ferocious defence against intruders.

Scientists theorized the reasoning behind these strange defense tactics and concluded that the wasps are using the ant carcasses as deterrents from possible predators. Ants emanate strong pheromones as communication mechanisms and these scents linger for a period of time after their death. The smell of the lifeless bodies serves as an adequate deterrent for animals attempting to eat nesting larvae.

This analysis results in the subsequent reasoning that female wasps must actively seek out and kill live ants as opposed to collecting their dead bodies. This theory was confirmed by the 13% lower parasitism rates in bone-house nest as compared to nests of similar species.

 

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We all know that spiders make webs but the Australian leaf-curling spider builds two additional houses to provide her with a den as well as a nursery for her babies. After making a web, the female chooses a suitable dead leaf. She lines the leaf with spider silk and curls it to form a little den that is closed at the top and open at the bottom. She hangs it in the centre of the web and waits inside for passing prey.

When she is expecting babies, she curls another leaf and hangs it away from the web in the midst of foliage.

The spider is also eco-aware! She uses not just fallen leaves but also discarded scraps of paper or other waste material to make her shelters.

 

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The female of the montezuma oropendola of Central America builds one of the most elaborate nests in the animal kingdom. Using vines, the bird weaves a large basket-like nest that hangs from trees. The nests are anchored with the strongest vines, and bits of fibre and other vines are added as finishing touches. They are built in a group, forming a huge colony.

To keep away predators, nests are constructed on isolated trees and are suspended from the flimsy ends of the branches to deter monkeys. The oropendolas also take care to locate their nests inhabited by hornets!

 

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Four species of solitary bees in Turkey and Iran make a three-tiered shallow underground nest called a ‘flower sandwich’. The outside layer is made of petals, and then a lining of mud is applied, ending with a layer of petals for the innermost chamber. A store of nectar and pollen is deposited in his chamber for the larva to eat when it hatches. The egg is laid and the chamber is sealed by bending the petals forward and slathering the whole thing with mud! Each bee bower has room for just one egg.

The sandwich keeps the larva’s food moist. When the baby bee has eaten, it spins a cocoon and hibernates for ten months. By the time spring arrives, the chamber hardens like a nut, protecting the bee from predators and from collapsing inwards.

The bees emerge only to mate, build another nest and lay an egg, before they die.

Scientists found that the bees in Turkey pick pink, yellow, blue and purple petals while the ones in Iran favour only purple!

 

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