Some wasps lay eggs in caterpillars as a means of reproduction. These are known as parasitoid wasps that use caterpillars as food sources for larva until fully emerged.
Wasps of the ichneumonidae, braconidae, and glyptapanteles species are known to use caterpillars as a living food source for their larva.
All wasps of these families lay eggs either on or in caterpillars eventually killing caterpillars as their fluids are used as a means of survival for wasp larva.
The number of grown larvae laid on each caterpillar varies. Its estimated glyptapanteles family wasps lay up to 80 grown larvae on caterpillars. Some wasp species can lay a lower number of eggs in or on caterpillars.
Some wasps only lay 14-18 eggs on caterpillars. In rare instances, wasps only lay one egg on the caterpillar.
Larva laid on caterpillars has a considerably higher chance of developing into fully-grown wasps as research suggests in the glyptapanteles and similar parasitic wasp species.
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Why Do Some Wasps Lay Eggs in Caterpillars?
Higher survival rates and the development of a larva into wasps is the main reason why wasps lay eggs in caterpillars. Research shows mortality rates are a few times higher in larva that isn’t hosted by a caterpillar.
As a result, some wasps use caterpillars as a source of food. Most importantly, this is a living source of food that is often controlled by the larva.
How Do They Lay Eggs in Caterpillars?
Most wasps that lay eggs on caterpillars are typically interested in butterfly and moth caterpillars. They inject eggs either on the surface or inside the caterpillar by piercing its soft tissue. After hatching, the eggs that have penetrated the host start to eat it gradually.
Wasps also need to avoid caterpillar defense mechanisms to sting or to lay eggs. Most wasps need to stay clear of caterpillar venom and their barbed hairs.
Most larva then becomes fully-grown wasps. Only a handful of larva remains on the host, mainly to manipulate it further.
All caterpillars used in the process eventually die. Their death is quick, but there’s sufficient time for the larva to emerge into fully adult wasps. Caterpillars start losing their appetite in the first stage before weakening and eventually dying.
17 Wasps That Lay Eggs in Caterpillars
The following wasps have been shown to use caterpillars as a food source for the larva.
1. White Butterfly Parasite
This wasp (Cotesia glomerata) is part of the Braconidae family. It’s a proven species of wasps that parasitize caterpillars. They use butterfly larva or caterpillars to lay their eggs. The number of eggs laid on the caterpillar varies considerably.
Between 16 and 52 eggs are laid by this wasp species on a caterpillar, a bit less than the number of eggs laid by glyptapanteles.
2. Cystomastacoides kiddo
This yellow-golden wasp is also known for using caterpillars as a food source for its larva.
The female Cystomastacoides kiddo lays eggs inside moth caterpillars.
This is one of the newly-discovered parasitoid wasp species.
It has been discovered in Thailand in 2008. This species was named after a similarly-looking character of Beatrix Kiddo from the 2003 Kill Bill movie.
3. Aleiodes indiscretus
This species is typically interested in Gypsy moth caterpillars.
It deposits its eggs directly in the caterpillar. Then, the eggs pupate while the caterpillar starts to dry out. Adult wasps emerge leaving the caterpillar dry and dead.
4. Amblyteles armatorius
These wasps are very common in the summer. The female wasp uses caterpillars to lay eggs in.
The favorite caterpillar host of the species is the Noctuidae owlet moths.
This wasp species mostly lives in Europe. But its habitat is increasing in parts of the Middle East.
5. Diadegma mollipla
The species is known for using caterpillars as living food for the larva.
These wasps are known for their ability to search for caterpillars based on odors.
Certain odors attract these wasps to certain plants where caterpillars live. Diamondback moth larvae are the favorite caterpillar of the species.
6. Yellow ichneumon wasp
These species of wasps (Xanthopimpla punctata) are sometimes used in agriculture to control moths and caterpillars feeding on cereals and sugar cane.
Wasp of this Pimplinae species lay eggs on top of caterpillars feeding on these crops. These wasps can sting, mainly used as a defense mechanism.
7. Microplitis mandibularis
Noctuidae moths are the preferred species of the Microplitis mandibularis. Their caterpillars are used to lay eggs.
The eggs erupt and start spinning cocoons. These cocoons are then turned into fully-grown wasps.
The species has been identified in 1895 in Greenland.
8. Habrobracon hebetor
This species of wasps have been largely used in agriculture. It’s mainly a solution on crops and fields that are pesticide-free and chemical-free.
Since wasps use caterpillars of various species that can be used on different types of agricultural fields.
The larva of the Habrobracon hebetor is considered efficient at digesting protein. An enzyme-rich digestive system helps develop Habrobracon hebetor wasps consume and digest caterpillars.
9. Microplitis croceipes
This wasp species is common in the US, particularly in Georgia. It represents one of the most beneficial wasps to crops as it controls Heliothis zea populations.
This wasp uses caterpillars differently from other parasitoid wasps. It only lays one egg in each caterpillar.
The egg then pupates inside the caterpillar.
Feces odors are used by these wasps to locate caterpillars. They are considered some of the most tenacious wasps in terms of having the ability to distinguish between different types of odors
10. Diadegma semiclausum
This species of wasps are known for laying eggs on leaf-eating caterpillars.
It’s very common on caterpillars that feed on cabbage and cauliflower.
Highly common in India, the wasp lays its eggs on the caterpillar. It can then take up to 16 days for the wasps to emerge.
11. Ichneumon eumerus
This species of wasp has a more complex road to laying eggs on caterpillars.
It looks for Maculinea arion caterpillars which are typically eaten by ants.
This caterpillar is dragged by ants insider their nests. The wasp enters the nest and sprays a strong chemical substance that prompts ants to fight each other. When the caterpillar is free and the ants aren’t in their way, the wasp moves on to lay an egg on top of it.
12. Therion circumflexum
Pine hawk moths and other small caterpillar species are targeted by Therion circumflexum. This wasp is one of the most common when it comes to wasps that lay eggs in caterpillars.
Commonly found in Europe and Asia, the wasp species lays eggs directly in caterpillars.
This wasp is also known for its distinct looks. It has an orange and black elongated body and thin long legs which help it move quickly on plant leaves.
13. Cotesia congregate
These species of wasps are known for continuously looking for caterpillars.
Wasps of the Cotesia congregate species develop directly in caterpillars. They then spin cocoons until they pupate.
The wasps then emerge as young adults immediately looking for caterpillars to lay eggs in as well.
14. Orange Caterpillar Parasite Wasp
This species of wasp (Netelia producta) is known for its bright orange body.
It lays eggs on caterpillars but only next to the head. Its eggs are visible as they are brown. Most of the caterpillars the species likes are found in Australia.
15. Hyposoter exiguae
The larva of the Hyposoter exiguae lives in caterpillars. The eggs hatch inside the caterpillar. It then leaves the caterpillar with dry skin as a sign it has consumed its soft tissues to grow.
16. Vulgichneumon saturatorius
The species is closely tied in its habitat to its favorite flower, the hogweed. Most hogweeds are found in England and this is where this parasitoid wasp lives.
It’s also here that the wasp finds its favorite caterpillar, the Silver Y. It lays eggs on this caterpillar as a source of food for its larva.
17. Agrypon flaveolatum
This wasp species is a parasitoid of the winter moth caterpillar.
Winter moths have reached North America over the past century. Since they, these moths are considered damaging to native trees such as maple. This is why this wasp species is often used to control Winter moth numbers.
How Do Caterpillars Defend Themselves?
Caterpillars seem like defenseless creatures. But there are at least a few common methods in which caterpillars defend themselves. Some of these methods depend on the predator they are trying to defend against. However, the following techniques are often used against parasitoid wasps such as those above.
Bristly hairs are the first line of defense of caterpillars. Their coarse hair is sometimes venomous. However, the coarse hair also makes it look like caterpillars have spikes on them.
This is the main reason some predators such as wasps only sting the soft parts of the caterpillar as they try to stay away from them as much as possible.
Some caterpillars have venom glands. It is believed caterpillars collect venom through a series of toxins that they encounter on plants.
Caterpillars collect multiple types of toxins which then turn into venom. Small predators can be paralyzed or even killed by the venom.
A series of caterpillars have very distinct hairs. Barbed hairs on caterpillars get stuck in the approaching enemy which makes for a good line of defense and one of the few strategies caterpillars can use against predators.
Moving in groups
While not as common as other methods, it has been shown caterpillars stay in groups to avoid predators. They can form very long lines which aim to distract the predators and to increase their chances of survival both while moving and while staying put.
Building hiding places
Some caterpillars learn how to build or use hiding places. Since they like to consume leaves on plants and vegetables, caterpillars often find hiding spots nearby. Avoiding contact with the predator is their best line of defense.
It was believed whistling was used as a means of communication between caterpillars. But species such as the walnut sphinx moth can whistle which they use as a defense strategy.
It’s still not clear if whistling is one of the defense mechanisms of caterpillars against wasps. However, it is generally agreed that whistling can be used by caterpillars at least against birds.
Some caterpillars manage to stay safe from birds by whistling. Other research suggests whistling is only used by caterpillars to keep bats away.
Caterpillars such as those of the Saddleback species are also known for blending in with their environment. This is one of the first lines of defense for these caterpillars as they like to spend a lot of time on the green leaves they consume.
A large percentage of the body of these caterpillars is dark green, similar to a leaf. Its eyes are spotted so that many predators confuse these caterpillars as being part of the leave or of the plant they’re sitting on.
Wasps that lay eggs on caterpillars typically go through extensive efforts during their mating periods to find appropriate caterpillars. Moth caterpillars are among their favorite. They find these caterpillars on leaves or plants.
Most wasps are attracted by caterpillar odors which makes them stay and hunt in a specific habitat.
These wasps are known as parasitoid wasps as they are parasite species living off another species. Wasp lay at least one egg on caterpillars and a maximum of 80 eggs.
Almost all of these eggs turn into larva and then into wasps by spinning cocoons.
Wasps that lay eggs on caterpillars are considered parasitoids for moth species. But they can be considered helpful to humans.
Parasitoid wasps are used to control caterpillar damages in agriculture. Since caterpillars feed on leaves of many crops, parasitoid wasps are used against them by some farmers. Eggs can be laid on the caterpillar or injected into the caterpillar. Once the larva grows it takes over the caterpillar which is still alive in the first phase. The caterpillar eventually dies. A dry shell is all that’s left once the larva has eaten the caterpillar.