What Are Zombie Flies? A Beginner’s Guide

The entrance to a hive with honey bees

Zombie flies are tiny insects that parasitize arthropods like honey bees. These phorid flies lay eggs inside their victim, which develop into larvae and feed off the host’s insides.

Bees impacted by zombie flies are called ZomBees. They get their name from unusual behavior, like flying at night and walking outside the hive without purpose. The bee eventually dies as a result of zombie fly parasites.

  • Common name: Zombie fly
  • Scientific name: Apocephalus borealis
  • Family: Phoridae
  • Hosts: Arthropods like honey bees, bumble bees, and paper wasps.

What do zombie flies look like?

The adult zombie fly looks like a small fruit fly, measuring up to 2.9mm long. It has a pale yellow body with an orange spot on the abdomen. The insect’s wings are narrow and translucent, while its legs are light brown.

The zombie fly’s eggs and larvae develop inside the host’s body, making observation a challenge. The smooth larva reaches up to 3.5mm in length and is yellowish in color. The brown pupae are typically under 2mm long.

How do zombie flies affect honey bees?

Zombie flies lay their eggs in honeybee abdomens, which develop into parasitic maggots, feeding off the live bee. Beekeepers may notice a range of symptoms caused by pressure from the growing larvae on their internal organs and nervous system.

A colony affected by zombie flies may exhibit the following signs:

  • Disoriented bees crawling near the hive entrance or on sidewalks.
  • Bees leaving their hive at night, often flying around street lights like mosquitoes and moths.
  • Bees walking around in circles.
  • Dead bees lying on the ground near the hive.
Honey bees out at night attracted to a light.
Honey bees attracted to light

Life cycle of the phorid fly

  1. After mating, the female adult fly injects her ovipositor into a honey bee’s abdomen. She releases eggs for 2-4 seconds before withdrawing.
  2. Once the larvae hatch, they feed on the host’s hemolymph and flight muscles. It takes an average of 7 days for a larva to reach maturity.
  3. Up to 13 mature larvae exit the bee between the head and thorax. This step in the lifecycle occasionally decapitates the bee’s head.
  4. The final pupation phase occurs outside the host and lasts around 28 days. On completion, the pupae emerge as adult phorid flies.

How to test for zombie flies

Have you noticed signs of fly-parasitized honey bees? You can help combat this threat by providing valuable data to researchers. To test for zombie flies, follow this simple method:

What you’ll need:

  • Half-gallon plastic bottle
  • Safety light holder
  • Duct tape
  • Tweezers for handling the bees.
  • Jars to collect the bees.
  • Pen and labels.
  • Camera or mobile device to take pictures.
  • Paper and pen (or phone) to take notes.


Step 1: Follow the video instructions below to build a light trap.

Step 2: Place any captured dead bees in a sealed container away from direct sunlight.

Step 3: Check the container daily to see if small brown larvae or flies are present. If nothing emerges within two weeks, then your bees are clean.

Step 4: Any larvae, pupae, and flies observed should be photographed and reported to the Zombee Watch website. Even if no parasites result, report this information to the program.

Tips for using a light trap

Take care handling dying bees, as they may sting. Always use forceps or tweezers.

Beekeepers should place light traps well away from their hives as healthy bees may get attracted to the light.

Commonly asked questions

Do zombie flies only infect honey bees?

In the past, zombie flies primarily targeted wasps and bumble bees. However, they have jumped species infecting non-native honey bees in North America.

Will zombie flies destroy my colony?

While zombie flies are unlikely to wipe out an entire colony, their presence could make a hive susceptible to other diseases and pests. These flies may also transfer harmful pathogens like deformed wing virus and Nosema ceranae.

Are zombie flies harmful to humans?

Zombie Flies are not harmful to humans. They only infect and kill other insects, particularly arthropods.

Is there anything I can do to help combat zombie flies?

Scientists need more data from “citizen scientists” on the location and prevalence of Apocephalus borealis. Anyone in the United States can get involved by visiting the ZomBee Watch site.

What is zombie fly fungus?

Entomophthora muscae is a fungal parasite that infects flies, feeding on their bodies from the inside. It controls the fly’s behavior, causing it to climb to a high-up location (summiting), helping spread fungal spores to more flies.

Fast facts

  • There is a diverse range of roughly 4000 phorid species.
  • The phorid fly is a member of the family Phoridae.
  • The parasites leave the bee’s body around seven days after it dies.
  • Some phorid flies were introduced to the U.S. to control red fire ants.
  • They are also called scuttle flies or hump-backed flies.
  • Most phorids are scavengers living off dead insects and other organic matter.

Similar Posts