Basic 7 · Science · Life Cycles of Organisms
The Life Cycle of the Housefly
In this topic you will describe the structure of the housefly and its complete life cycle, and investigate its developmental stages through observation.
By the end of these notes you should be able to:
- Describe the main features of an adult housefly
- Describe the stages of the life cycle of the housefly
- Observe and record the developmental stages of the housefly
What you already know
- Living things and their characteristics
Copy everything that has a blue line on its left into your notebook. The other parts are for reading.
Lesson 1
- Strand
- Cycles
- Sub-strand
- Life Cycles of Organisms
- Indicator
- B7.2.2.1.1 – Describe the life cycle of the housefly
Introduction
The housefly is one of the most common insects in our homes, markets and refuse dumps. It is small but very important to study, because it can spread diseases.
1. Classification of the Housefly
The housefly (scientific name Musca domestica) is an insect. Like all insects, its body has three parts (head, thorax and abdomen), three pairs of jointed legs and one pair of antennae. Unlike many insects, it has only one pair of wings.
2. Main Features of the Adult Housefly
| Part | Description and function |
|---|---|
| head | carries the large compound eyes, antennae and mouthparts |
| compound eyes | large red-brown eyes made of thousands of lenses; detect movement |
| antennae | short; sense smell |
| proboscis | sponge-like mouthpart for sucking liquid food |
| thorax | middle part bearing the legs and wings |
| wings | one pair of transparent wings for flying |
| halteres | small knobs behind the wings that help balance |
| legs | three pairs with hairs and sticky pads for walking on walls and ceilings |
| abdomen | rear part containing digestive and reproductive organs |
3. How the Housefly Feeds
The housefly cannot chew. It vomits digestive juices onto solid food to dissolve it and then sucks up the liquid with its sponge-like proboscis. It feeds on almost anything: food, faeces, rotting matter and wounds.
4. Observing a Housefly Safely
Use a sealed specimen or a magnifying glass on a dead fly in a closed container. Do not touch flies with bare hands, and wash your hands after any activity involving flies.
New words
- insect
- An animal with three body parts, six legs and usually wings.
- compound eye
- An eye made of many small lenses.
- proboscis
- A tube-like mouthpart for sucking food.
- halteres
- Small balancing organs behind a fly's wings.
Summary
- The housefly is an insect with a head, thorax and abdomen, six legs and one pair of wings.
- It has compound eyes, antennae, a sponge-like proboscis and hairy, sticky legs.
- It feeds by vomiting juices onto food and sucking up the liquid.
Class activity: Specimen Study
- Observe a sealed housefly specimen with a hand lens.
- Identify and draw its main parts.
- Compare it with a picture of a mosquito.
You need: Sealed housefly specimen, Printed housefly life-cycle diagram, Printed housefly-stage cards
Exercises
Answer in your exercise book first, then check your answers.
1. How many legs does a housefly have?
- A. six
- B. four
- C. eight
- D. ten
Show answer
Answer: sixThree pairs.2. The housefly feeds using its…
- A. proboscis
- B. antennae
- C. wings
- D. halteres
Show answer
Answer: proboscisSponge-like mouth.3. The housefly has one pair of wings.
- A. True
- B. False
Show answer
Answer: TrueLike other true flies.4. The body parts of an insect are the head, thorax and ______.
Show answer
Answer: abdomenThree parts.5. State three features of the adult housefly.
Show answer
Answer: Compound eyes, one pair of wings, hairy legs with sticky pads (or proboscis, antennae).Any three.6. Explain how a housefly feeds on solid food.
Show answer
Answer: It vomits digestive juices onto the food to dissolve it, then sucks up the liquid with its proboscis.Feeding.
Lesson 2
- Strand
- Cycles
- Sub-strand
- Life Cycles of Organisms
- Indicator
- B7.2.2.1.1 – Describe the life cycle of the housefly
Introduction
A housefly does not hatch looking like an adult. It changes form completely as it grows, passing through four stages. This is called complete metamorphosis.
1. Complete Metamorphosis
Complete metamorphosis: A life cycle with four distinct stages: egg, larva, pupa and adult.
2. The Four Stages
| Stage | Description | Duration (warm weather) |
|---|---|---|
| egg | white, about 1 mm long, laid in batches of 75–150 on rotting matter or faeces | about 8–24 hours |
| larva (maggot) | white, legless and worm-like; feeds and grows rapidly | about 4–7 days |
| pupa | brown, hard case (puparium); the body changes inside | about 3–6 days |
| adult | emerges from the pupa; can mate after a few days | lives about 2–4 weeks |
3. How Fast Flies Multiply
A female housefly can lay about 500 eggs in her lifetime. In warm weather, the whole cycle takes only about 7 to 10 days. This means flies can increase very quickly where there is rotting food and waste, which is why refuse dumps and open toilets are often covered in flies.
4. Conditions Needed for Breeding
Flies breed in warm, moist places with decaying organic matter, such as refuse heaps, animal dung, open latrines, rotting fruits and kitchen waste. Removing these breeding places is the most effective way to reduce fly numbers.
5. Comparing Metamorphosis
Not all insects undergo complete metamorphosis. Grasshoppers and cockroaches have incomplete metamorphosis, with three stages: egg, nymph and adult. The nymph looks like a small adult without wings. Houseflies, mosquitoes, butterflies and beetles have complete metamorphosis, with a pupa stage in which the body is completely reorganised.
New words
- metamorphosis
- A change in body form during the life cycle.
- larva
- The worm-like young stage of an insect.
- pupa
- The resting stage in which the larva changes into an adult.
- maggot
- The larva of a fly.
Summary
- The housefly undergoes complete metamorphosis: egg, larva, pupa and adult.
- The cycle can be completed in about 7–10 days in warm weather.
- Flies breed in warm, moist, rotting matter such as refuse and dung.
Class activity: Life Cycle Wheel
- Arrange printed cards of the four stages in a circle.
- Write the duration and description of each stage.
- Explain why flies multiply quickly.
You need: Sealed housefly specimen, Printed housefly life-cycle diagram, Printed housefly-stage cards
Exercises
Answer in your exercise book first, then check your answers.
1. The larva of the housefly is called a…
- A. maggot
- B. caterpillar
- C. tadpole
- D. nymph
Show answer
Answer: maggotFly larva.2. Which stage comes after the larva?
- A. pupa
- B. egg
- C. adult
- D. nymph
Show answer
Answer: pupaResting stage.3. The housefly undergoes complete metamorphosis.
- A. True
- B. False
Show answer
Answer: TrueFour stages.4. The four stages are egg, larva, pupa and ______.
Show answer
Answer: adultFinal stage.5. Describe the pupa stage.
Show answer
Answer: A brown, hard case in which the larva changes into an adult over 3–6 days.Pupa.6. Explain why removing refuse reduces the number of houseflies.
Show answer
Answer: Refuse is where flies lay eggs and maggots feed; without it, they cannot breed.Breeding sites.
Lesson 3
- Strand
- Cycles
- Sub-strand
- Life Cycles of Organisms
- Indicator
- B7.2.2.1.1 – Describe the life cycle of the housefly
Introduction
Scientists learn by observing. By carefully watching a safe, sealed set-up, you can see how a housefly changes from egg to adult.
1. A Safe Observation Set-Up
- The teacher prepares a sealed, transparent container with a small piece of fish or fruit as bait, covered with fine mesh.
- The container is kept in a safe place away from food areas.
- Learners observe through the clear sides every day for about two weeks without opening it.
- Learners record the date, the stage seen and any changes in a table.
- At the end, the teacher destroys the container and its contents safely.
2. Sample Observation Table
| Day | Observation | Stage |
|---|---|---|
| 1 | tiny white eggs on the bait | egg |
| 2 | small white wriggling maggots | larva |
| 5 | larger maggots moving away from the bait | larva |
| 7 | brown, barrel-shaped cases | pupa |
| 11 | adult flies inside the container | adult |
3. Drawing Conclusions
From the observations, learners conclude that the housefly passes through egg, larva, pupa and adult stages, that the larva stage is the feeding and growing stage, and that the whole cycle takes about ten days in warm conditions. Comparing results from different groups makes the conclusion more reliable.
4. Scientific Skills Used
This investigation uses the skills of observing, recording, measuring time, comparing and concluding. Scientists always record observations carefully and honestly, even when results are unexpected.
Safety: Never open the container. Wash your hands after the activity. The teacher must destroy the flies and bait at the end.
New words
- investigation
- A planned scientific study.
- observation
- Information gathered by watching carefully.
- conclusion
- A statement of what the results show.
- reliable
- Giving the same results when repeated.
Summary
- A sealed container with bait allows safe observation of the housefly life cycle.
- Daily records show the egg, larva, pupa and adult stages.
- Observing, recording and concluding are key scientific skills.
Class activity: Class Observation Record
- Observe the sealed container daily with the teacher.
- Record each stage seen in your exercise book.
- Write a conclusion at the end of two weeks.
You need: Sealed housefly specimen, Printed housefly life-cycle diagram, Printed housefly-stage cards
Exercises
Answer in your exercise book first, then check your answers.
1. What should you do after any activity with flies?
- A. wash your hands
- B. eat immediately
- C. touch your face
- D. open the container
Show answer
Answer: wash your handsHygiene.2. At about which day did pupae appear in the sample table?
- A. day 7
- B. day 1
- C. day 2
- D. day 11
Show answer
Answer: day 7From the table.3. The container should be opened daily to check the flies.
- A. True
- B. False
Show answer
Answer: FalseKeep it sealed.4. Information gathered by watching carefully is an ______.
Show answer
Answer: observationScientific skill.5. Name four scientific skills used in the investigation.
Show answer
Answer: Observing, recording, comparing, concluding.Any four.6. Why is it useful to compare results from different groups?
Show answer
Answer: It makes conclusions more reliable by checking whether results are consistent.Reliability.
Homework
- Draw the life cycle of the housefly and write the duration of each stage.