Topic: insects

Author: Elżbieta Szedzianis

Target group

Students of the 6th grade of an elementary school

Core curriculum

6) Arthropods. Student:

A) presents the living environment, morphological characteristics and lifestyle of crustaceans, insects and arachnids, and indicates adaptive features that enable them to master different environments,

B) makes observations of arthropods (photos, films, patterns, etc.) and presents common features of this group of animals,

C) explains the importance of arthropods (including parasitic forms and pests) in nature and for humans.

The general aim of education

The students describe the external structure of an insect, its adaptation to the living environment, and performing life functions, and the meaning of insects.

Criteria of success

• You will observe stick insects and describe their body structure, provide three adaptations to the living environment, and one adaptation to food intake,

• recognize and indicate the characteristics of arthropods (4) and insects (4) observed in the stick insects.

Key competences

• communication in foreign languages;

• communication in the mother tongue;

• mathematical competence and basic competences in science and technology; 

• learning to learn.

Methods / techniques

Mind map, lboratory work, work with text.

Individual work, work in groups.

Teaching aids

• e‑textbook;

• interactive or traditional board;

• tablets/computers;

• work cards;

• specimens of stick insects: adults, larvae, eggs;

• magnifying glasses.

Lesson plan overview (Process)

Introduction

1. The teacher asks the students to use a mind map and present the characteristics of arthropods. The teacher presents the criteria for work evaluation: The work is in accordance with the characteristic plan It contains a description of the following:

• Arthropod structure,

• body coverage,

• two groups of organisms classified as arthropods, with features allowing them to be distinguished,

• meaning of arthropods.

The students create the maps on free sheets of paper, sign them and the teacher collects maps for evaluation.

2.The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

3.The teacher explains that the students:

• will learn the next group of arthropods on the lesson - insects,

• insects have all the characteristics of arthropods and characteristics that are only attributed to them,

• will conduct an observation to justify the afore‑mentioned.

Realization

The teacher divides the students into groups of six people. Each group receives a closed jar in which there is food, an adult stick insect, 2 larvae of various sizes, and eggs of stick insects.

1. Observation 1

The teacher asks the students to observe an adult stick insect.

Observation goals:

• demonstration that the stick insect is an arthropod,

• listing the characteristics of insects observed in stick insects.

During the observation, the students can use the abstract to confirm that they correctly indicate the characteristics of insects. The students get a work card with a schematic drawing of a stick insect, on which they indicate and sign the characteristics of arthropods in green and in blue for insects. The students do interactive exercise No. 2.

2. Observation 2

The teacher asks the students to use illustrations 2 and 4 to observe and determine what type of mouth apparatus and legs can be found in stick insects.

3. Observation 3

The teacher asks the students to look at the eggs and larvae of the stick insects taken from a farm. Using gallery 2, the students are to determine the type of development of stick insects. In the work card, they write down the course of the development and its type. The students do interactive exercise No. 3.

4. Observation 4

On the basis of the observation, the students determine how stick insects are adapted to the life on land, feeding, what defensive adaptations they have. They write down the findings in the table in the work card. The students do interactive exercise No. 4.

Summary

1. The teacher displays gallery 1 on the screen. The teacher asks the students to indicate the characteristics of arthropods, insects and the adaptation of insects to the environment in the observed insects.

2. The teacher asks the students: what else do you need to learn about insects so that you are happy with your knowledge?

Homework for keen students.

Do interactive exercise 1.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Arthropods - insects

Insects account for 90% of species of all animals. They are also the most diverse group. Like other arthropods, they have their bodies covered with a chitinous cuticle and segmented legs, as well as segmentation marks in the structures of the thorax and the abdomen. The vast majority of these animals live on land and have wings thanks to which they can fly. Some insects, such as ants, cockroaches, fleas, do not have wings but move quickly, running or jumping. Few insects, such as some water beetles and bugs, live in water.

Insects’ bodies are divided into heads, thorax and abdomen. On the head there is a mouth organ and sensory organs: 1 pair of antennae and eyes. Antennae are segmented, thread‑like or finger‑like processes that are used to receive tactile, olfactory and sound stimuli. On the body of insects there are 3 pairs of crotch legs and usually 2 pairs of wings.

The structure of insect mouths depends on the type of food they eat, and the method of its collection and grinding. In the biting mouth there are strongly developed serrated mandibles and jaws. This type of mouth is found both in herbivorous insects such as grasshoppers, locusts and herbivorous beetles, as well as in predatory insects such as dragonflies, mantis. Bees and bumblebees have a biting‑and‑licking mouth. Its elements are strong mandibles that allow biting and flattening food or other substances (e.g. wax), and a long, hairy tongue used to suck nectar and collect water. The suction mouth is found in butterflies and consists of a long, thin, spirally coiled suction proboscis used to collect liquid nectar.

Parasites such as mosquitoes, fleas, lice and aphids have a piercing‑and‑sucking mouth. It consists of a scissor‑like element (labella) that allows piercing the tissues of the host's body, as well as a suction and saliva tubes (labium) used to suck up liquids, e.g. blood, vegetable juices. The licking mouth of a fly is used for wetting and licking food. It consists of a tube ending with a tongue.

The legs of insects reflect their lifestyle. Cursorial legs are elongated and thin, usually ended with claws, sometimes pads that allow moving on flat, slippery surfaces (house fly). In grasshoppers, fleas and lice, the rear pair of thorax legs is adapted for jumping. Jumping legs are characterized by a strong elongation, a broad, muscular upper part and a relatively thin, slender lower part. Raptorial legs are found in mantis and dragonflies. They are always front, elongated, massive legs with a serrated inner surface, and are used to hold a prey. Some insects have very flattened legs. In a mole cricket, the front pair of legs is very wide and resembles a shovel. Additionally, they are equipped with numerous spikes and cloves, which are useful when digging underground corridors (digging legs). In water beetles and bugs, the rear legs are flattened. On their surface there are hairs that increase the surface of the legs and make them similar to a fin, which makes the insects swim well (swimming legs).

Wings allow insects to move in search of food and escape from predators. They are membranous skin folds that are a flight organ. In beetles and bugs, the first pair of wings is transformed into massive wing covers that have protective functions. Wings grow out of the thorax and usually occur in 2 pairs (butterfly), sometimes one (fly) or none (wingless insects). They are made of a membrane stretched over a network of tubes that give them their shape and stiffen them. Their colour can be defensive.

Insects breathe using trachea – tubes of various diameters, which branch out, form a spatial system inside the body that also penetrates into the wings. From the inside, trachea are reinforced with chitin spirals that provide them with rigidity and maintain a constant patency of the entire system. The air enters them through spiracles – small holes arranged on the sides of the body, and then goes inside the animal. Most insects pump the air into the trachea by rhythmically moving the abdomen. The trachea have closed ends filled with fluid in which respiratory gases dissolve. This is where the gas exchange takes place.

Insects most often have eyes composed of straight eyes, the number of which can reach up to 30,000. Each, regardless of the other ones, registers the intensity of light. The image is created in an insect’s brain as a result of the connection of signals coming from individual eyes. Hence, images that insects see do not have clear outlines and highlighted plans. Insects receive changes in light intensity, movement and colour in a wider range than the human eye. For example, they see an invisible part of the spectrum of light – ultraviolet. Insects with excellent eyesight, such as dragonflies, have short antennae that are mainly organs of the chemical sense: smell and taste, but also touch. The more branched they are, the more receptors they can fit, allowing an insect to receive odours from long distances. The male can sense the smell of a female from a distance of up to 10 km.

Insects are dioecious.

Insects undergo complex development in which there are several larval stages. The larvae gradually transform into an adult (imago). In some insects (grasshoppers, dragonflies, mantises or lice) the larvae resemble an adult form. However, they are smaller, usually have no wings and are not sexually mature. In their case we deal with incomplete metamorphosis. In the vast majority of insects (butterflies, beetles, bees, wasps, flies and fleas) the development proceeds with complete metamorphosis. Their larvae are not similar to the adult form. They eat a lot and often moult, stepping up the size of the body. After reaching the appropriate size, they are transformed into motionless chrysalis. In many insects, the chrysalis can be surrounded by a cocoon – a structure made of thin threads that are formed in special silk glands of the larvae. Inside the chrysalis, the larva transforms into an adult. This involves a complete re‑structuring of the body. Adult insects usually do not live long. They breed, sometimes take care of their offspring, and then grow old and die.

Insects are of great importance in nature. Many species of these animals, such as bees, bumblebees and flies, can pollinate most flowering plants, including crops important to humans. Without their help, these plants would not be able to produce fruit and produce seeds. Insects are also a source of food for many animals, mainly vertebrates, but also arachnids and other insects. Many of them feed on dead organic matter (e.g. many species of flies), manure of animals (e.g. dung beetle) or carrion (e.g. various species of beetles), which contributes to cleansing of the environment.

Herbivorous insects are usually perceived negatively by humans, because they cause huge losses in plant crops (e.g. cabbage periwinkle, potato beetle). Some species also eat stored food (flour millweed and grain weevil). Certain beetles, aphids and moths are plant parasites, and fleas, lice and bedbugs feed on animals and humans.

Many insects carry microbes that cause deadly diseases: mosquito – malaria, human louse – typhus, and tse‑tse fly – African coma. A human may also die as a result of a sting of a bee, a wasp or a hornet, if the person is allergic to venom.

Some insects provide valuable resources for humans. Bees produce honey, beeswax and putty, and mulberry silkworms spin cocoons from which silk is produced.

• Insects are the largest group of animals.

• Insects are arthropods that have a body covered with a chitinous cuticle, divided into a head, a thorax and an abdomen, 3 pairs of segmented legs, one pair of antennae and (in most cases) wings.

• The structure of insects depends on the environment, lifestyle, type and manner of feeding.

• Insects usually breathe using trachea.

• Insects reproduce sexually, undergo complex development with complete or incomplete metamorphosis.

• In the development with complete metamorphosis there is a still pupa and movable larva unlike imago.

• Insects are an element of almost all food chains.