Aphids are one of the few creatures on earth that don’t need sex to produce babies. So how do aphids reproduce asexually? And if they can do it, why then do they sometimes do it sexually too? Let’s find out
Aphids are a type of insect that belongs to the Aphidoidea superfamily. These insects extract sap from plants, and you might also know them as greenflies or blackflies.
The reproduction process of aphids tends to be rapid and quite complex at the same time. They are one of the few creatures on earth that can alternate between sexual and asexual reproduction.
Scientists call this parthenogenesis, and the only others who can do this include the wasp, bees, ants, and a few small invertebrates.
To make it even more complex, they only alternate between these methods in certain conditions. For example, fall is the season for sexual reproduction, whereas spring is the season for asexual reproduction.
Aphid Life Cycle
The life cycle of aphids is known as holocyclic, which is science-speak for the fact that they are sometimes sexual, and sometimes asexual.
During spring, the aphid eggs hatch, and the baby aphids are born only as females. They grow and become juvenile aphids (nymphs). Before adulthood, they molt four times before adulthood.
These adult aphids are “stem mothers” that give birth to another generation of female aphids. All through summer, they produce wingless female nymphs.
In late summer, the last lot of stem mothers produce male aphids for a very specific purpose – the male help to fertilize eggs that aphids lay in preparation for winter.
You see, adult aphids cannot survive harsh winters – but their eggs can! That’s why it is important to have male aphids and lay eggs – it ensures that the next generation of aphids overwinters as eggs and survives the harsh weather.
The final generation of aphids lay eggs, which overwinter and hatch in the spring, thus ensuring the continuity of the species.
Do Aphids Lay Eggs?
Yes, aphids do lay eggs, but mostly because eggs can overwinter. Its not the main way they reproduce – that they do it through cloning (which we cover next).
Their tiny and elliptical eggs are easy to find if you know where to look for them. Look on the underside of leaves or on plant stems of their host plants. This is where female aphids lay eggs and stick them for safekeeping.
The eggs are also of many colors – sometimes you will find black ones, and other times you might find yellow or orange eggs.
Scientists might be trying their best to master cloning to produce a liver or heart for humans, but these bugs have it all figured out already – Aphids can clone themselves!
Cloning is a part of the life cycle of aphids, and aphids create nymph clones of themselves most of the year instead of laying eggs like most of the insect world.
Female aphids have XX chromosomes. Male aphids only have the X chromosome and no Y chromosome. This is why male aphids are said to have XO chromosomes.
The aphid clones have XX chromosomes, just like their mama’s. As you might have noticed – they don’t need anything from the male aphid to be born (unlike in humans).
Female aphids create entire generations by cloning during the summer and spring without any need for a male.
Interestingly, cloning is much quicker than laying eggs, so aphids can recreate a whole colony very quickly when they are at it.
But what happens when there are too many aphids on one host? We get to the next amazing superpower of these bugs – flying!
Aphids live on host plants, on which their entire life cycle happens, but they can also change host plants sometimes.
Aphids migrate from a host when the plant has too many of them and no longer has the nutrition to support all. But unlike fleas or springtails, they cannot jump on to another plant. So what is an aphid to do?
This is when some of the newer generations start being born with wings. These winged females fly to a different host plant and then colonize it.
However, once their purpose is solved, they stop making more winged offspring, and the nymphs that come afterwards are again wingless. Researchers call this “dimorphism” and attribute it to both genetic and environmental conditions.
Winged aphids may be sexual females, but they don’t reproduce as fast as the wingless ones (perhaps it takes more time to clone if you are flying around).
This means that other insects can colonize the host plant before they can. Wingless females can reproduce both asexually and sexually.
In the fall, like all creatures, aphids start to prepare for winter. But unlike ants who collect food for the winter, aphids decide to go one step ahead – they prepare to lay eggs.
Female aphids start to create babies without one chromosome (the males). These males take a while to mature, but once they are ready, the male aphids start to mate with females.
The females then lay aphid eggs and lay them on the host plants.
Now, we mentioned earlier that male aphids have XO chromosomes instead of XY chromosomes.
This means that even those aphids born out of sexual reproduction cannot be males; they will always be females.
At this point, you might wonder why male aphids are at all necessary when the females can clone themselves.
Well, it is necessary because winters can be harsh, and adult aphids do not survive in the cold for too long. However, their eggs can survive the cold.
Sexual reproduction produces fertilized eggs and ensures that a new generation of aphids can be born after the winter. These eggs stay dormant during winter and only hatch when it is warm enough, continuing the life cycle.
Frequently Asked Questions
How do aphids reproduce both sexually and asexually?
All aphid species can reproduce both sexually and asexually in different seasons. Sexual reproduction occurs in the fall.
But during most of the year, over spring and summer, aphids reproduce asexually, creating clones. Sexual reproduction is required to produce eggs which can survive the winter, unlike the aphids themselves.
Is an aphid asexual?
Aphids are among the few organisms that can reproduce both sexually and asexually, in response to changes in season.
That’s why aphids reproduce rapidly in spring and summer but you can hardly see their infestations during the winter. During the summers, they clone themselves (which is quicker), but during the winter, they produce eggs instead.
How do insects reproduce asexually?
Aphids reproduce asexually by cloning. All female aphids can clone with XX chromosomes. This process of cloning gives rise to multiple asexual generations.
It is only towards the end of the reproductive period that male aphid are born. These are simply aphids that are missing an X chromosome.
How often do aphids reproduce?
Aphids reproduce throughout the year, except for very cold months. Females lay aphid eggs for most warmer periods and can give birth to as many as twelve clones per day!
This is why aphid infestations spread so rapidly in gardens and plantations during spring and summer. But during winters, you would find them completely missing.
Aphids are very common, and one reason is their amazingly adaptable reproduction process. The grain aphid, green peach aphid, and pea aphid are among some of the most common pests in America.
If you come across aphids, don’t treat them just as pests. These tiny bugs have one of the most interesting of life cycles. We hope this article helps you understand them better. Thank you for reading!
Over the years, our readers have sent us several emails on this topic. Please go through them below.
Letter 1 – Aphids
Subject: What is this?
Location: Douglasville ga
November 10, 2015 2:15 pm
These bugs are all over a lily plant that is going dormant for the winter… They are mostly on the underside of the leaves?!?
Signature: Angela M
Your plants are infested by Aphids. Aphids are considered especially troublesome by gardeners as they feed by piercing the surface of the plant and then sucking fluids. Aphids also reproduce without mating, and a female Aphid can give live birth to young. The mature winged Aphids are generally both sexes and they can also reproduce by mating.
Letter 2 – Aphids
Subject: Mystery Green Eggs on Flowering Plum Tree
Location: St. George, UT, United States
March 3, 2016 4:49 pm
I was examining the new flowers on my flowering plum tree when I noticed these little green eggs. As you can see, they are rather easy to notice against the dark leaves of the tree. I would like to know if they are helpful or harmful, and how to get rid of them if they are bad. Thanks!
Signature: – Ami D.
Though they are quite small, the “green eggs” you observed are actually Aphids. In addition to normal sexual reproduction, Aphids are also capable of reproducing without mating and laying eggs. According to BugGuide: “Over-wintering eggs hatch in the spring into wingless females. These wingless females are parthenogenetic (reproduce without fertilization) and hold eggs in their bodies to give birth to living young. Their offspring are similar to the females, but some develop wings. Near autumn male and female wingless forms are born. These mate and the females lay fertilized overwintering eggs. Males can be winged or wingless; parthenogenetic females are usually wingless. In warm climates, living young may be produced continually.” Aphids are considered pest insects by most gardeners. They have sucking mouthparts and they feed on fluids in plants, robbing the plant of both nutrition and moisture. Though we don’t normally provide extermination advice, in our own garden we try to control Aphids by spraying infested plants with mild, soapy water.
Letter 3 – Aphids
Subject: What is this
March 29, 2016 12:34 pm
Just curious to know what this is. I found it on one of my tomato plants.
Signature: Andrew Chace
You have Aphids on your tomato plants.
Letter 4 – Aphids
I am hoping you can help me identify the spiny little critters that have taken up residence on my eggplants. Sorry the picture is not real clear, but it does show their yellow and brown stripes, and the spikes that cover them all over. I live in San Diego, California. How can I get rid of them without using some harmful chemical? Would insecticidal soap work?
Thanks for your Help,
Your eggplants have an infestation of Keelbacked Treehoppers, Antianthe expansa, in the nymph stage. The adults are green winged creatures that have sharply keeled backs and sharp spines on each side of the head. The nymphs are black and orange and spiny as indicated in your photo. The nymphs are very sensitive to approaching danger and migrate to the other side of the stem en masse away from the hands of the gardener or any other perceived danger. They feed on the sap of solanaceous plants including eggplant, tomatoes and peppers. Treehoppers, which belong to the insect order Homoptera, are related to aphids, cicadas, mealybugs, scale insects and leafhoppers. You can try picking them manually, but beware the sharp spines, or you can spray the plants with a mild solution of soapy water.
Letter 5 – Aphids
have an infestation of bugs on my willow tree. They are dark gray with black spots and shaped kind of like a light bulb. The narrow part at the head. The back legs are longer than the front and they have little antennae. There are thousands clustered together. Can you tell me what they are and how to treat them?
Sorry about the delay. I believe you have Giant Willow Aphids, Pterochlorus viminalis. This is a large species, reaching about 1/4 inch. It is gray with black spots, short black horns on the abdomen and a large tubercle in the middle of the abdomen. It feeds in large, compact colonies on the trunks and branches of willows often near the ground, and when disturbed has the habit of kicking the hind legs back and forth above the abdomen in a very energetic manner. This habit is common to all the individuals of a colony and is probably a means of warding off natural enemies according to Essig. Try your local nursery for a treatment. Here is a site with great information and photos.
Letter 6 – Aphids
I need your help please. Where I live in California, my house in like in the middle of a field. With some trees around the house and for grass it’s all dried old weeds no green grass! We just started cleaning the yard (field) up and besides wolf spiders, and earwigs and ants etc. we’ve noticed a lot of these bugs that fly leap from the weeds and trees. I want to call them ticks but I haven’t found a tick picture that looks like these. They are brown and also bright neon green. The body is hard and the head is like a triangle. Please help me soooooooon if you can. Thanks.
Up to my knees in bugs.
You are being bothered by leaf hoppers Family Cicadellidae or spittle bugs Family cercopidae, both of which will feed off the sap of plants but will not harm people. Spittle Bugs leave frothy foam on plant stems that resembles spittle and serves as a shelter for the feeding nymphs.