Aphids at a Glance
If you've ever looked under the leaf of a flower or plant and found a cluster of tiny insects, you've most likely encountered aphids. Aphids are small sap-sucking bugs that feed on plants. They reproduce quickly, giving the scientific world plenty of opportunities to study them, and in turn providing us with a lot of information on these creatures. Let's investigate.
The sex life (or non-sex life) of the aphid is one of their most unusual features. Some aphids reproduce sexually, some reproduce asexually, and some use both methods of reproduction, depending on their environment. With asexual reproduction, females can either give birth to live clones or lay eggs, all without a male aphid.
For the aphids that do involve a male, it gets a little more complicated, but also more interesting. After laying eggs or creating clones, the new females are able to produce copies of themselves as well. When the weather heats up, some of the eggs hatch into males. When the males are sexually mature, they can mate with the female aphid, who then produces eggs that will survive over the winter and hatch into more aphids.
Aphid Life Cycle
Since some aphids use asexual reproduction and others use sexual, while still others use both, there are a few different paths their life cycle may take. The cycle is also affected by environmental factors. The average lifespan of an aphid is one month. Let's look at the different paths in more detail.
1. Holocyclic Life Cycle
In a holocyclic life cycle, the aphid starts as an egg that is usually planted before winter. From there it hatches into a fundatrix, which is a wingless female aphid. Next, the fundatrix will create daughter clones. These females will then go on to create both males and females. These males and females mate and create an egg that can survive the winter.
In an anholocyclic life cycle, female aphids simply create live birth clones of themselves without the help of males. So the life cycle usually looks like this: a female aphid, which sometimes has wings and sometimes does not, creates a clone called an aptera. This aptera is unwinged and can survive the winter, then goes on to continue the cycle by creating more clones.
3. Host Changing
Some aphids change the host plant on which they make their home, causing their life cycle to differ slightly from others. They start out as eggs, which hatch into fundatrices. These fundatrices create viviparous females, which means that they create the next generation inside their bodies, which are then born fully formed but smaller than the parent. This generation is where the magic happens. These females create the sexupara, which fly back to the original host and deposit both male and female aphids. These aphids mate to create the overwintering eggs, starting the entire cycle again.
To keep it a bit more straightforward, we have organized this into the following bullet points:
- Viviparous females who travel to a new host
- A new generation of viviparous females are created here
- The sexupara are born
- The sexupara then fly back to the old host and deposit both male and female aphids
- The male and female aphids mate and create eggs that start the process over again
Okay, let's take a moment to review what we've learned about aphids, which are small sap-sucking bugs that feed on plants. We learned first about their reproduction and then about their entire life cycle.
We learned that aphids can reproduce sexually, asexually, or even take advantage of both methods. In sexual reproduction, a male and female are both required. For asexual reproduction, only females are involved. For aphids that use both asexual and sexual reproduction, the temperature, food availability, as well as whether they change host can affect the involvement of sex.
The life cycle of the aphid can be holocyclic or anholocyclic. Anholocyclic life cycles involve generations of females simply cloning themselves into aptera. In holocyclic life cycles, the females eventually create males and females who can mate and create eggs that survive the winter and then hatch into a fundatrix, which is a wingless female aphid.
Host changing is an aspect that affects the life cycle because a generation of the aphids will fly to a new host where they create a generation of females who can in turn create both males and females.
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Aphids: Discussion Questions
In this activity, you'll check your knowledge regarding the reproduction and life cycle of an aphid.
For this activity, print or copy this page on a blank piece of paper. Then, carefully read the given narrative and provide a written response to the questions that follow. You may use the web to search for ideas in answering the questions.
Aphids are small sap-sucking insects that vary widely in color from green, black, brown, pink, to almost colorless. They puncture the phloem vessel in a plant and feed on the sap using sucking mouthparts called stylets. The majority of these insects are wingless. Although they are considered pests, aphids are essential to some species of ants. These farming ants protect large herds of aphids by fighting off aphid predators. In return, the ants milk the aphids by stroking them with their antennae. This action will cause the aphids to release honeydew, a sweet excretory product. The honeydew is so valuable to the ants that they do everything to maintain the population of aphids. In winter, ants store aphid eggs in their colony. In spring, the ants carry the newly hatched aphids back to the plants, thus maintaining their honeydew farms.
- What type of aphid reproduction is described in the scenario?
- Give a reason why aphids reproduce sexually and asexually.
- Differentiate the two types of aphid lifecycle.
- Why are aphids essential to some ant species?
- How do ants ensure that their aphid farms are sustainable during winter?
- Eggs are produced by an aphid sexually and asexually.
- Aphids adjust how they reproduce depending on external factors, such as a change in temperature and lower food quantity or quality that leads to host changing.
- An anholocyclic life cycle involves a female aphid creating a clone of itself, helping generate future clones. In contrast, a holycyclic life cycle starts from eggs that hatch into male and female offspring. As they mature, they will then undergo sexual reproduction to produce eggs.
- Aphids are essential to ants since they are a source of honeydew.
- To ensure that they have aphids to farm, ants will bring aphid eggs to their colony and nurture them until spring.
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