My Science School

More than beautiful, monarch butterflies contribute to the health of our planet. While feeding on nectar, they pollinate many types of wildflowers. The flowers they chose are varieties that are brightly colored, grow in clusters, stay open during the day, and have flat surfaces that serve as landing pads for their tiny guests. Monarch butterflies are also an important food source for birds, small animals, and other insects.

The vivid markings of the monarch butterfly (Danaus plexippus) serves as a “skull and crossbones” warning, signaling “Poison!” to the butterfly’s predators. Female monarchs lay their eggs on the underside of poisonous milkweed leaves. As the caterpillar hatches, it eats its own egg; then switches to a diet of milkweed leaves. The milkweeds’ toxins remain permanently in the monarch’s system, even after the caterpillar metamorphoses into a butterfly. Animals that eat a monarch become very sick and, thereafter, will avoid this distinctively patterned butterfly.

Monarch butterflies live mainly in prairies, meadows, grasslands and along roadsides, across most of North America. The adult butterfly drinks nectar from a variety of flowers, uncoiling and extending its long proboscis to sip food. When not in use, this flexible “tongue” coils back into a spiral.

Most monarchs will live only a few weeks, but the generation that emerges in late summer and early fall is different. These butterflies are born to travel and may live for eight or nine months to accomplish their lengthy migration. Scientists think the monarchs use the position of the sun and the changing weather to know when it’s time for their long journey.

Credit : National Park Service

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Dragonfly, (suborder Anisoptera), also called darner, devil’s arrow, or devil’s darning needle, any of a group of roughly 3,000 species of aerial predatory insects most commonly found near freshwater habitats throughout most of the world. Damselflies (suborder Zygoptera) are sometimes also called dragonflies in that both are odonates (order Odonata).

Young dragonflies, called larvae or sometimes nymphs or naiads, are aquatic and are as dedicated predators under water as the adults are in the air. The functionally wingless larvae are usually mottled or dull in colour, matching the sediments or water plants among which they live. They have bulging eyes somewhat similar to the adults, but possess a formidable anatomical structure not present in the adult. Called the “mask,” it is a fusion of the larva’s third pair of mouthparts. Disproportionately large, the mask folds beneath both the head and thorax when it is not in use. At the end of the mask is a set of fanglike pincers used to seize prey such as worms, crustaceans, tadpoles, and small fish. Different species of dragonfly larvae can be described as sprawlers, burrowers, hiders, or claspers. Their shape, metabolism, and respiration differ concordantly with the microhabitat they occupy.

Larvae crawl from eggs laid in or near water. Some species lay their eggs inside plant tissue, others attach their eggs to substrates at or above the water’s surface, and some may drop or wash their eggs from their abdomen onto water. Larvae absorb oxygen from the water using gills inside the rectum. The abdomen draws water in and pumps it out again through the anus. Water can be forcibly expelled in this way, resulting in jet propulsion as a means of escape. Solid waste is also expelled in this manner. As the larva grows, it molts, its future wings first becoming apparent about halfway through the larva’s development. These wing sheaths then enlarge rapidly with each successive molt. Eventually, the larva crawls out of the water (often at night) and molts one last time, emerging as an adult and leaving behind a cast skin (exuvia).

Many dragonfly families have descriptive common names associated with their scientific names. Examples include the hawkers (Aeshnidae), petaltails (Petaluridae), and clubtails (Gomphidae). Numerous other names related to neither taxonomy nor fact have traditionally been applied to dragonflies, such as horse stinger. Dragonflies have also been known as “snake doctors” in the American South, owing to the superstition that they nurse ill snakes back to health. The term devil’s darning needle is derived from a superstition that dragonflies may sew up the eyes, ears, or mouth of a sleeping child, especially one who has misbehaved. In reality, dragonflies present no danger to humans.

Credit : Britannica 

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Both butterflies and moths are winged insects. And, at a glance, they do seem similar. However, with just a bit of observation you can tell one from the other. How?

One of the easiest t ways to tell a butterfly from a moth is from the way they rest. Butterflies tend to fold their wings vertically up over their backs, while moths hold their wings flat in a tent-like fashion that hides the abdomen. While at rest, you can also see how their bodies and antennae are. Butterflies are slender and smooth, while moths are stout and fuzzy. Butterfly antennae are thin with club-shaped tips as against the feathery or comb-like antennae of moths. Also, normally butterflies come in vibrant colours and moths in dull colours. Another difference between them has to do with their wings. Butterfly wings are not linked, but the forewings and hindwings of moths are connected by a bristle-like structure called the frenulum. Butterflies are diumal, meaning they fly in the daytime, and moths are nocturnal, flying at night.

Another difference between butterflies and moths has to do with their pupal stage between the larva stage and the adult stage- rather than their physical structure. Butterflies form a chrysalis that's hard, smooth, and silkless, while moths create cocoons spun from silk.

However, all the above do not mean there are no exceptions because there are dull-coloured butterfly varieties and extremely colourful moth varieties too. There are butterflies resting with their wings held flat and moths that rest with wings held up. There are crepuscular butterflies that fly at dawn and dusk, and diumal moths. The list goes on....

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Ants are social animals. They communicate with each other using a chemical scent called pheromones. They rely on pheromones to defend territories and exchange information such as the location of food sources and nest sites. Like other insects, ants perceive smells with their long and thin antennae. The antennae provide information about the direction and intensity of scents.

In species that forage in groups, a forager marks a scent trail to find its way back to its colony - similar to Hansel from Hansel and Gretel leaving a trail of bread crumbs through the woods to find his way back home. On the way back to the nest carrying food, the ant creates a trail with an even stronger scent. This trail is followed by other ants. These followers then reinforce the trail when they head back with food to the colony. Thus ants are often seen marching one after the other.

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A keystone species is one that has an incredibly important role to play in an ecosystem. Without this species, ecosystem would be dramatically different or may even stop existing altogether. It can be any organism, from large animals to microscopic bacteria. In short, a keystone species is what holds a habitat together.

There's a call to protect the tiger because as a keystone species, this top predator plays a significant role in the health and diversity of an ecosystem.

If it disappears, the population of its prey - usually ungulates - will go up, and this will result in the decimation of vegetation, leading to a collapse of the ecosystem.

Not just animals, birds and insects, even plants can be keystone species.

Mangroves are a keystone species that firm up shorelines and reduce erosion. They provide a safe haven and feeding area for small fish among their roots, which reach down through the shallow water.

It is true that if bees go extinct, so would humans. This keystone species plays a very important role in keeping the world going.

As the most important pollinators, they are responsible for about a third of the world's total food production. Without bees, there would be food shortage, and eventual human collapse.

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When it rains, we get to see several types of creatures we may not see otherwise. In the last few weeks, especially in Tamil Nadu and Kerala, one creature has made headlines for showing up in large numbers due to the rains. But it's not really good news. Why? Come let's find out.

It is possible that you've seen the giant African snail. Especially around the time it rains. With its large, striped shell firmly on its back, you may have spotted it crossing a wet road, climbing a gate, or munching on some plant. As the name suggests, it is native to Africa, and can grow to be a large snail. And it is one of the most invasive species in the world, and is said to have landed in India several decades ago inadvertently. That they have no natural predators has played a big role in their numbers increasing. Today they are found in several States, including Tamil Nadu, Kerala, Karnataka, Andhra Pradesh, and the North-East regions too. They eat native plants and crops, altering the ecosystem and denting farmers' income. It is said that they consume even paint! They are not just pests , they are also a health hazard to humans. They can cause severe diseases as they host parasites. For this reason, they cannot be consumed by humans.

Did you know?

• Just a few months ago, a village in Kerala's Alappuzha district came up with a novel plan to get rid of this invasive species, which causes extensive damage to crops. Onam bumper tickets with a chance to win Rs. 12 crore were on offer for 10 people catching the highest number of snails.
• Recently, after witnessing the continuing menace of these snails, a group of walkers in Kerala made an announcement to buy these snails each for a rupee from residents. Apparently, within just a few days, they bought over 3,500 snails!

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Is the destruction of wetlands driving out these magnificently colorful insects?

Dragonflies are very sensitive to changed in the environment .loss of the marshes swamps and free flowing rivers they breed in are some of the risk factors.

What a new report says...

The destruction of wetlands is driving a decline of dragonflies around the world with one sixth of species of the magnificently colorful insects threatened with extinction conservationists said on Thursday.

A report from the International Union for Conservation of Nature presented the first assessment of all 6,016 dragonfly and damselfly species globally, and found that at least 16 per cent of them risked going extinct.

What's driving the extinction?

The decline is a symptom of widespread loss of the marshes, swamps and free flowing rivers they breed in driven mainly by the expansion of unsustainable agriculture and urbanization around the globe, IUCN said in the update of its "Red List of threatened species.

"By revealing the global loss of dragonflies, today's Red List update underscores the urgent need to protect the world's wetlands and the rich tapestry of life they harbor. IUCN director general Bruno Oberle said in a statement

Why are wetlands disappearing?

Globally, these ecosystems are disappearing three times faster than forests. A report published three years ago by the Ramsar Convention on Wetlands found that 35 per cent of the world's wetlands were lost between 1970 and 2015, Wetlands store carbon, protect against floods and offer habitats for one in 10 of the world's known species.

What are the warning signs?

The welfare of dragonfly species is an especially good indicator for how the wetlands are doing.

"They're very, very sensitive to changes in the environment. And so that is an early warning signal to what's happening to wetland systems around the world." Craig Hilton-Taylor, who heads IUCN's Red List unit said.

He said a lack of data meant the true number teetering on the brink of extinction could be as high as 40 per cent.

Where the problems loom large...

The situation is particularly dire in South and Southeast Asia, where more than a quarter of all dragonfly species are threatened, IUCN said.

This is largely due to the clearing of wetland and rainforest areas to make room for crops like palm oil, it explained. Pesticides, other pollutants and climate change are also growing threats. AFP

The red list

• With the latest update, the Real List now includes assessments of 142,577 species of animals and plants, including 40.084 considered to be threatened with extinction.
• This marks the first time that the number facing the highest risk has passed 40.000

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