Odonata Honor

Nature Study

Requirements

What are the main differences between dragonflies (Anisoptera) and damselflies (Zygoptera)?
Answer: Dragonflies: robust body, wings open at rest, strong flight. Damselflies: slender body, wings folded against the body at rest, weak flight. Eyes touching (dragonfly) or separated (damselfly). — Anisoptera (unequal wings) has hind wings larger than the forewings. Zygoptera (equal wings) has both alike. Dragonflies fly up to 50 km/h; damselflies 5-10 km/h. The dragonfly's eyes touch on the head; the damselfly has eyes with a gap between them. Both have aquatic larvae. The order Odonata has 5,500+ species worldwide. Identification helps in current ecological studies.
Approximately how many species of dragonflies exist in the world?
Answer: Approximately 5,500 species of the order Odonata exist in the world. In Brazil there are more than 800 cataloged species. Distributed among more than 30 different families. — Odonata is one of the oldest orders (300+ million years). Brazil has 14% of the world's Odonata diversity. Researchers discover new species annually — the Amazon is a biodiversity hotspot. The National Museum in Rio's collection, destroyed in 2018, held thousands of Odonata specimens. Enormous current scientific importance.
Cite 5 names by which dragonflies are known in different parts of your country.
Answer: 5 Brazilian names for dragonflies: lavadeira, cavalo-de-judeu, cavalinho, jacinta, helicóptero, donzelinha (regional). Each region of Brazil uses different names. — Lavadeira is the most common name in SP/MG. Cavalo-de-judeu is traditional in the Northeast. Cavalinho-do-diabo is the popular name in RS/SC. Jacinta is used in some regions. Helicóptero is a modern name because of the hovering flight. Donzelinha applies only to Zygoptera. Brazil has a wealth of regional names. Knowing local names aids both scientific and popular communication.
Draw the life cycle of a dragonfly and indicate where it lives in each phase.
Answer: 3 stages: egg (in water), nymph/larva (in water for 1-5 years preying on insects), adult (on land/in the air flying to reproduce). Draw and indicate the habitat of each stage. — The cycle is incomplete metamorphosis (no pupa). Eggs are laid on aquatic vegetation. Nymphs live 1-5 years at the bottom of ponds/rivers, breathing through gills. They climb up to emerge, shed their exoskeleton, and dry their wings. The adult lives 2-8 weeks flying, hunting other insects in the air. It reproduces in flight. It returns to the water to lay eggs. The complete cycle is important.
Describe the 5 main parts of the anatomy of dragonflies.
Answer: 5 parts: head (eyes + antennae), thorax (legs + wings), abdomen (10 segments), 4 membranous wings, and 6 legs. Typical insect structure adapted for hunting flight. — The head is almost entirely filled by compound eyes (30,000 ommatidia each). The thorax has 6 legs and 4 independent wings (each moves on its own). The long abdomen (10 segments) facilitates reproduction in flight. The eyes detect motion in 360°. The mandibles crush prey. Each part is specialized for an exemplary predatory aerial life among modern insects.
What is the average lifespan of dragonflies, in the larval stage and in the adult stage?
Answer: Larval: 1-5 years (up to 7 in some species) in the water. Adult: 2-8 weeks (rarely up to 6 months) flying in the air. The larval stage is much longer than the adult stage. — Surprisingly, the dragonfly spends 90%+ of its life as an aquatic nymph. They grow by molting their exoskeleton several times. When they emerge as adults they live only weeks — the reproduction period. Natural predators (fish, toads, birds) reduce life expectancy. Fossil dragonflies had wingspans of up to 70 cm 300 million years ago in the Carboniferous.
Why are dragonflies considered excellent bioindicators?
Answer: Dragonflies need clean water to reproduce. Their presence indicates good environmental quality. They are sensitive to pollution, pesticides, and deforestation. Their absence is a warning of degradation. — A bioindicator is an organism whose presence/absence indicates the quality of the environment. Dragonflies require water with dissolved oxygen > 5 mg/L (non-polluted). Larvae die with even light pollutants. A healthy igapó/floodplain has dozens of species. A polluted river has 0-2 species. Researchers monitor water using Odonata as an indicator. Brazil has a national bioindication program.
Cite 5 different natural prey of dragonflies. Approximately what percentage of its weight does it eat daily?
Answer: 1) Five prey: mosquitoes, flies, moths, small butterflies, and other flying insects (the nymph, in the water, eats aquatic larvae, tadpoles, and small fish). 2) Percentage of weight per day: the dragonfly is voracious and can eat per day the equivalent of about 20% (or more) of its own body weight, capturing dozens to hundreds of mosquitoes. — The dragonfly is a great natural predator of mosquitoes, helping with pest control — a benefit to the balance of the environment and to humans.
Cite 5 natural predators of dragonflies.
Answer: Five predators: insectivorous birds, toads and frogs, lizards, spiders (which catch them in their webs), and fish (which prey mainly on the nymphs in the water). Larger insects and even larger dragonflies also prey on them. — Like every species, the dragonfly is part of a food chain, serving as food for various animals.
Describe the eyes of dragonflies and their functionality.
Answer: Dragonflies have two large compound eyes that occupy nearly the entire head, made up of thousands of units called ommatidia (which can reach about 30,000 in each eye). This gives them a field of view of nearly 360°, excellent motion perception, and color vision (including ultraviolet). They also have three small ocelli on top of the head, which help stabilize flight. — Exceptional vision is the dragonfly's main hunting weapon, allowing it to locate and capture prey in mid-flight.
How many times per second can a dragonfly beat its wings?
Answer: The dragonfly beats its wings at a relatively low frequency, around 30 times per second (approximately 20 to 40 beats per second) — far fewer than mosquitoes and bees — thanks to its large wings and powerful musculature. The four wings move independently. — The independent movement of the wings gives the dragonfly precise flight, capable of hovering in the air and changing direction quickly.
On average, how many hours per day can a dragonfly fly?
Answer: The dragonfly spends most of the day active, accumulating several hours of flight during warm, sunny periods — alternating between hunting, territory patrol, and mating. Because it depends on heat to fly, it is active mainly during the day. — Being an insect that regulates its temperature through the environment, the dragonfly concentrates its flight hours during the warmest moments of the day.
What is the estimated maximum flight speed of dragonflies?
Answer: The estimated maximum flight speed of dragonflies is around 50 km/h, with some large species able to reach about 50 to 60 km/h in bursts — placing them among the fastest flying insects. — The high speed, combined with great maneuverability, makes the dragonfly an extremely efficient hunter.
List 3 uses of dragonflies for humans.
Answer: Three uses: (1) natural pest control, devouring mosquitoes (including those that transmit dengue and malaria) and other insects; (2) bioindicators of water and environmental quality, since the nymphs only live in clean water; (3) scientific and educational value — studies of their flight and vision inspire technology, in addition to aesthetic and ecological value. — More than just beautiful, dragonflies provide important ecological services, controlling pests and indicating the health of aquatic environments.