Do black ants eat monarch eggs?

Black ants can sometimes prey on monarch eggs and caterpillars, but they are not a major threat to the monarch population. Monarch eggs and larvae have some defenses against ant predation, and monarchs have co-evolved with ants over time.

Do black ants eat monarch eggs?

Yes, black ants are opportunistic predators that will eat monarch eggs and larvae if they come across them. However, black ants do not seek out monarch eggs to eat them exclusively. They consume eggs and larvae incidentally when foraging, rather than specifically targeting monarch breeding sites.

Some key facts about black ants eating monarch eggs:

  • Black ants (species like the black pavement ant and black garden ant) will consume monarch eggs or larvae if they encounter them while out foraging.
  • However they do not actively hunt for monarch eggs – eggs are just part of their generalist diet.
  • Monarch eggs and larvae have some defenses against ants, like chemical compounds in their bodies.
  • But ants can overpower these defenses if they come upon an unprotected egg or caterpillar.
  • Monarch egg predation by ants is one source of mortality, but likely less significant than threats like wasps, birds, and weather.

So in summary, black ants do sometimes eat monarch eggs and larvae, but they do not specifically target them. Monarch breeding success relies more heavily on finding well-protected sites away from generalist insect predators like ants.

Do ants seek out monarch eggs to eat them?

No, there is no evidence that ants seek out monarch eggs specifically as a food source. Ants are opportunistic foragers – they search broadly for any food sources and do not zero in on monarch eggs and larvae in particular.

Here are some reasons why ants do not specifically hunt monarch eggs:

  • Ants rely a lot on chemical trails to find food. Monarch eggs do not produce strong chemical trails that would attract ants.
  • Ants do not have specialized adaptations or behaviors to locate hard-to-find monarch eggs.
  • Monarch eggs provide minimal nutritional value. Ant colonies can find easier, more substantial food sources.
  • Monarchs lay eggs singly on milkweed plants, making it unlikely ants would find a lot of eggs in one place.

In some cases, ants may return to a plant where they previously found monarch larvae. But in general, ants do not have advanced mechanisms to seek out monarch egg locations. Their strategy is to broadly forage for any available insects or sugars.

How often do ants attack monarch eggs?

There are not precise estimates on how frequently ants attack monarch eggs. But based on observations, monarch eggs are not a primary food source for most ant species.

Factors that influence how often ants may prey on monarch eggs include:

  • Abundance of milkweed – If milkweed is widespread, eggs will be more dispersed and less likely to be encountered by foraging ants.
  • Accessibility of the monarch eggs – Eggs laid higher up on milkweed plants are less accessible to ants.
  • Size of local ant populations – Areas with more ant nests and foragers would likely have higher rates of egg predation.
  • Availability of alternate prey – Ants will eat whatever prey is most abundant and easy to find.

Overall, monarch eggs and larvae do experience some predation by ants, especially if eggs are laid close to the ground. But ants do not search for monarch breeding sites and can only prey on eggs they randomly come across while foraging. So for monarchs, choosing good egg laying spots is important to limit ant attacks.

Do ants communicate about finding monarch eggs?

There is no evidence that ants actively communicate to other members of their colony about finding monarch eggs or caterpillars. Ants use chemical pheromones to signal about food sources, but monarch larvae do not produce substantial chemicals that would trigger signaling.

However, ants may incidentally communicate monarch prey locations in some cases. Communication would likely only happen if a significant concentration of larvae was found in one place. Possible communication methods include:

  • Tandem running – One ant leads one or more nestmates to the larvae directly.
  • Laying an unscented pheromone trail on the ground as it returns to the nest.
  • Regurgitating food to nestmates to spread the scent.
  • Brief antennation between foragers to spread scent.

But again, ants do not have specific signals reserved for monarch prey. And finding a large grouping of larvae in one spot would be rare since monarchs lay eggs singly. Any communication about monarch eggs within an ant colony would be incidental and not a deliberate strategy to target monarchs.

How do monarch eggs defend against ants?

Monarch eggs and larvae have some adaptations that help defend them from ant predation, though they are still vulnerable. Their main defenses include:

  • Chemical compounds – Eggs and larvae contain cardenolides that are distasteful or toxic to some predators.
  • Egg placement – Females lay eggs singly and often on the underside of leaves or hidden spots to avoid detection.
  • Larval thrashing – Older larvae will violently twist and whip their heads if disturbed.
  • Camouflage – Eggs blend in with milkweed plants and larvae have disruptive coloration.

These defenses make monarch larvae less appealing as prey and more difficult to find and attack. However, ants may still be able to overpower the chemical taste deterrents and access well-hidden eggs. The defenses provide some protection but do not make monarch eggs invulnerable to ant predation overall.

Do chemical compounds in monarch eggs deter ants?

Monarch eggs and larvae contain cardiac glycosides, which are natural chemical compounds that are toxic to some predators. These cardenolides can deter or impair predatory insects and other animals.

However, ants have relatively high tolerance to the cardenolides found in monarchs. The chemical defenses offer some protection, but do not fully deter ants. Some key points:

  • The cardenolides taste unpleasant but are not lethal to ants at concentrations found in monarch larvae.
  • Ants can detect the bitter taste and may avoid eating monarch larvae at first.
  • But ants can develop tolerance if exposed repeatedly and will still attack larvae.
  • The chemical defenses are stronger in older larvae and pupae than eggs.
  • So eggs likely have minimal chemical protection – their main defense is camouflage.

In general, the cardenolides provide some discouragement to ants but are not a foolproof protection method for monarch eggs and larvae against ant predation.

How do female monarchs protect their eggs from ants?

Female monarch butterflies use some specific strategies to try to protect their eggs from predators like ants. These include:

  • Laying eggs singly – Monarchs lay one egg per milkweed plant, widely spacing them out to avoid creating dense concentrations of vulnerable offspring in one place.
  • Placing eggs carefully – Females prefer to lay eggs on the underside of leaves away from easy access points for predators.
  • Selecting isolated plants – Monarchs often choose isolated milkweed plants rather than clusters, to avoid ant nests and foraging trails nearby.
  • Constant movement – Females rarely lay more than one egg in a location, quickly moving far away to spread eggs out.

Additionally, some monarchs may lay “dummy eggs” along with fertile ones as decoys for predators. The dummy eggs look identical but do not hatch. By using these strategies, monarchs try to give their offspring the best chance of survival against ant predation.

Do ants impact monarch populations?

Ant predation on monarch eggs likely has only a minor impact on overall monarch populations. Monarchs have evolved defenses to limit ant attacks, and they have many other predators that are a greater threat.

Reasons why ant predation is not a major threat to monarchs:

  • Ants are opportunistic predators and do not specifically target monarch breeding sites.
  • Monarch chemical defenses provide some protection against ants.
  • Monarchs have reproductive adaptations to spread eggs widely.
  • Wasps, birds, and other specialist predators likely eat far more eggs/larvae than ants.
  • Habitat loss has a bigger impact on monarchs by limiting milkweed.

So while ants may eat some monarch eggs and caterpillars they come across, focused conservation efforts on limiting ant access is unlikely to have a major impact on boosting monarch populations compared to addressing other threats.

Do ants ever benefit monarch populations?

While ants prey on monarch eggs, they can also sometimes benefit monarch populations. Potential positive effects include:

  • Remove monarch parasites – Ants will eat fly larvae and other parasites on monarch caterpillars, improving caterpillar survival.
  • Protect caterpillars – Aggressive ants may protect monarch caterpillars from other insect predators.
  • Pollination – Ants can sometimes pollinate milkweed flowers, increasing milkweed seed production for monarchs.
  • Ecosystem engineers – Ant nests and burrows help aerate soil and cycle nutrients to support milkweed growth.

However, most of these interactions likely have only minor or localized benefits for monarchs. The parasitism and predation pressures ants impose are greater overall than any advantages they provide monarchs in most cases.

Do any ant species specialize in eating monarchs?

There are no ant species that specifically target monarch eggs and larvae as their main food source. No ants have evolved specialized adaptations to seek out and overcome monarch defenses.

A few factors prevent ants from specializing on monarch prey:

  • Monarch eggs are small and scattered, providing little substance.
  • Their chemical defenses, while limited, require some tolerance.
  • Developing complex hunting for solitary, well-hidden eggs is unlikely.
  • Milkweed provides no other nutrition ants need beyond the larvae.

Generalist ant species opportunistically eat monarch eggs, but no ants rely on them as a primary food source. The challenges of finding and overcoming their defenses prevents such specialization from evolving.

Wasps like the braconid wasp are specialist predators of monarchs and pose a much larger threat. But ants are primarily opportunistic foragers, not specialized monarch hunters.

Do different ant species threaten monarchs more than others?

Some ant species pose more risk to monarch eggs and larvae than others. In particular, smaller ants that can access leaves more easily or aggressive ants near milkweed plants are key threats.

Ant species that especially threaten monarchs include:

  • Thief ants – Very small so can access leaf undersides and hidden eggs.
  • Little black ants – Forage on plants often so encounter eggs.
  • Pavement ants – Large nests with persistent foraging in prime monarch habitat.
  • Fire ants – Aggressively guard and prey on insects near their nests.
  • Argentine ants – Displace native ants and monopolize the best habitat.

Bigger ants like carpenter and harvester ants rarely eat monarch eggs. Tiny thief ants are likely the biggest ant threats overall based on their access and appetite for eggs. But any ant species can opportunistically eat monarch eggs if they come across them while foraging.


In conclusion, black ants and some other ant species do occasionally prey on monarch eggs and larvae. But ants do not actively hunt for monarch eggs or have specialized adaptations to find them. Monarch eggs seem to comprise only a small portion of overall ant diets.

Monarch butterflies employ strategies to protect their offspring from ant predation, including chemical defenses, camouflage, and scattering eggs widely. Ant attacks are one source of egg and larval mortality, but monarchs face more substantial threats from habitat loss and specialist predators like wasps.

Targeted conservation efforts to reduce ant predation pressure are unlikely to provide major population benefits for monarchs. Maintaining milkweed habitat abundance and diversity will better counter the opportunistic threat from ants and other generalist insect predators.

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