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Honey Bees Swarm Early

Shaku Nair, Shujuan Li, Dawn H. Gouge
Department of Entomology, University of Arizona

With the early onset of summer in Arizona, bee activity is peaking early (March), leading to a surge in swarming behavior. Have you recently come across a large cluster of bees that appeared suddenly? Read on to learn more about honey bee swarming, what it involves and what to do if you come across a swarm.

Figure 1. A traveling mass of honey bees is called a swarm, and they can stop to rest in the strangest places! Photo: allouphoto, Adobe Stock.

What is honey bee swarming?

Swarming is a natural process by which honey bee colonies split to reproduce and expand their populations, and a traveling mass of bees is a swarm. As spring days lengthen, and temperatures increase, new sources of pollen and nectar from plants stimulate the rearing of brood and honey bee colonies eventually become overcrowded. This necessitates swarming. Swarming is common during spring and continues throughout the year while pollen and nectar sources support growing colonies. This is greatly influenced by environmental conditions.

In an active honey bee colony, there is a single queen. The queen is rarely seen outside and hardly ever needs to fly. She stays deep inside the comb, cared for by the worker bees, and lays eggs continually. Honey bee queens produce a pheromone that inhibits the production of new queen bees.  But as the colony becomes increasingly crowded the pheromone fails to make it to all the bees, or older queens begin to produce lower levels of the pheromone. Uninhibited worker bees create larger elongated rearing cells called queen cups. Once eggs in the queen cups hatch, the larvae are given special care and are fed with a food called royal jelly. Worker bees tending the existing queen give her less food, and egg production slows as the queen loses bodyweight, which will ultimately help her to fly. When new queens are almost ready to emerge from the queen cups, the old queen takes most of the workers and departs. This traveling mass of bees is called a “swarm” (Fig. 1).

How does swarming occur?

Before leaving, the workers fill their stomachs with honey, and this is the only food the swarm has to sustain activity until they find a new home site in which to establish their new colony. The old queen, being a weak flyer, will often land suddenly, and often not far from the original location. Resting swarms can be found clustered on the ground, on a fence post (Fig. 2), a tree limb (Fig. 3), the side of a building (Fig. 4), or other locations, and workers will quickly surround the queen to regulate her temperature. Since swarming bees are focused on finding a new home, they are not generally defensive and rarely pose any danger to humans or other animals.

Figure 2. A honey bee swarm on a fence post. Photo: Vasily Reinkymov, iNaturalist.org.



 Figure 3. A honey bee swarm on a tree limb. Photo: pncphotos, Adobe Stock.

Figure 4. A honey bee swarm on a building wall. Photo: Poiseau Philippe, Adobe Stock.

How big is a swarm and how long do they last?

Swarms can vary in size and shape (Fig. 5). They can be small, about the size of a softball to basketball-sized or larger aggregations. Clusters can be round, oval or oblong, or have no definite shape. The bees can be loosely distributed over a surface in the beginning and gradually come together in a few hours. Swarms can last a few hours to a few days, depending on how soon they can decide upon a location for their new home.

Photo: Danijel, Adobe Stock.

Photo: Vasily Reinkymov, iNaturalist.org.

Photo: Darios, Adobe Stock.

Figure 5. Swarms can vary in size and shape.

What happens to the old colony after a swarm leaves?

Back in the original colony, the first new queen to emerge will sting and kill other emerging queens. The old colony usually has enough food reserves to last for a while, but it is important to start building up the number of worker bees. The new virgin queen will mature after several days and fly out to seek drones in areas called “drone aggregations”. She will mate multiple times with several drones and will store sperm for the remainder of her lifetime. After mating, she will return to the nest and start laying eggs, slowly building up the colony. Sometimes newly emerged virgin queens will leave the nest with a group of workers in another swarm, called an “after swarm”, and this can occur repeatedly until the old nest is depleted and dies off.

How to differentiate between a swarm and a colony

Both swarms and colonies can have large numbers of bees and can be difficult to differentiate. But swarms are more often seen in odd shapes and places than colonies. The bees in a swarm are not foraging for food yet, and so will not have yellow or orange pollen evident in pollen baskets on their hind legs. They are also docile at this time, because they do not have a nest and brood to protect. They may appear stationary but are very active and may even be heard buzzing from a distance. This means that a lot of communication is occurring about important matters concerning their potential nest, such as nest location and food sources around it. However, they do not appear to move in and out of a specific spot, which could be the colony entrance. 

Figure 6. Bees moving in and out of a specific spot like this tree cavity, can indicate the presence of a colony within. Photo: Bob, Adobe Stock

On the other hand, bees in a colony are very focused. If you see many bees flying in and out of a specific spot, this indicates the presence of a colony within (Fig. 6). They forage for pollen and have yellow or orange pollen balls on their hind legs. Once a swarm finds a suitable home site, they start to build comb and rear brood, and the workers become more protective. 

Problems arise when they establish a colony in a place where they pose a risk to people (Fig. 7). In this situation, wild honey bees can become pests because of sting incidents, defensive bee attacks, and the structural damage and annoyance that their foraging and nest-building activities can cause. The chances of people getting stung in such situations are much higher once brood are being reared.

Figure 7.  Bees have set up a colony inside this mailbox. Photo: tallonr99, iNaturalist.org.

What to do when you see a resting swarm?

• It is best to leave swarms alone if they are in a spot that does not have much human traffic passing close by. Using caution tape to designate the area off-limits until the queen is ready to fly again. Swarms usually move within 24-72 hours.
• However, if a resting swarm is found on public property or around a residence in the way of people (Fig. 8) it may be necessary to have the swarm removed by professional beekeepers or a pest management professional. Local beekeepers or beekeeping associations may help.
• Most states have their own beekeepers’ association, and many are active on social media. Some beekeepers will collect swarms and use them to start new hives. Information for the Arizona Beekeepers Association can be found at https://www.azbeekeepers.org/. The website provides a list of beekeepers that might be able to assist with bee removal.
• If swarms are disturbed, they will disperse within a local area, and this can cause people to panic. Workers in a swarm are generally docile but can sting if disturbed. When this happens the best course of action is to have an experienced beekeeper remove and relocate the bees or have a pest management professional take an integrated pest management approach.

Figure 8. These bees have come to rest on this shade structure, which could be risky to people in the area. Photo: Lucag_g, Adobe Stock.

Key points to keep in mind regarding bees in Arizona

• Peak Swarming (March-June): Large, football-sized clusters of honey bees are common. While these swarms are usually searching for a new home and are relatively docile (unless disturbed), they can appear suddenly.

• Africanized Behavior: Virtually all wild bees in Arizona are Africanized and must be considered as such. They are highly territorial, respond to vibrations/noises (like lawnmowers), and will defend their nests aggressively.

• Heat Stress & Foraging: As desert plants bloom, they are active, but extreme heat can kill them and cause hives to "melt" (wax failure). They are frequently seen around pools, fountains, and air conditioning units for water.

• Nest Locations: Honey bees can nest in the weirdest places, such as irrigation or water meter boxes, block walls, under roofs, in old tires, even in landscape or construction debris. 

What are some other reasons we see large aggregations of bees?

Bearding (Heat Management)

Sometimes, bees can be seen clustering outside their hive (Fig. 9). This is merely to reduce internal heat and congestion of the hive during hot days. The bees return inside when the temperature drops. 

Figure 9. Bees “bearding” outside their hive is a way to reduce internal temperature. 
Photo: Meredith, Adobe Stock.

For more information on honey bee swarms, and managing wild honey bees in your environment, refer to our publication. Wild Honey Bees in Community Environments – Identification, Biology, and Reducing Risks (arizona.edu)

Grasshopper Swarming?

Have you seen unusually large numbers of grasshoppers recently? A significant, early grasshopper outbreak is occurring in March 2026 across Arizona, specifically in the Phoenix, Tucson and Yuma areas, with increased activity also reported in Southern California. The outbreak is characterized by large numbers of young grasshoppers appearing weeks ahead of the typical late-spring schedule.

The major species noted is the pallid-winged grasshopper (Trimerotropis pallidipennis). This is a species native to western states with a range from southwestern Canada, down through the desert southwest U.S., Mexico, and into Argentina. They are medium to large sized grasshoppers that blend well into the desert landscape, dull brown in color with dark brown bands (Fig. 10).

Figure 10. Pallidwinged grasshoppers blending into urban landscapes. Photo: Dawn H. Gouge.

As spring progresses into summer, the grasshoppers are attracted by irrigated landscape plants and residential lights during nighttime flights and move in large numbers into towns. They feed on various shrubs, herbs and grasses depending upon what plants are available. They will also feed on cultivated crops including vegetables, alfalfa, mile, barley, cotton, and corn. Eggs laid the previous year hatch in early spring and the young hoppers feed on annual grasses initially, switching later to other plants.

Climate trends towards milder and drier winter months favor the survival of grasshoppers, with arid regions of the western states at the highest risk. In the low desert regions of Arizona, nymphs develop rapidly from February through April, and adults are often noticed moving into towns in April or May. Causes for the unusually early high populations include the wet winter/fall which created ideal conditions for their egg survival and abundance of vegetation that serves as food sources. This year, the unusual heat wave in February and March warmed up the soil faster, triggering a mass hatching of eggs leading to an earlier start to grasshopper activity.

Pallid-winged grasshoppers are strong fliers, which enables them to disperse widely as their food sources dry out and they have to seek other sources. In towns and cities pallid-winged grasshoppers find supportive conditions in areas with bare or rocky ground and weedy vacant lots where they can go unnoticed unless they are disturbed and fly.

Should you be worried about large numbers of grasshoppers?

While generally harmless to humans and pets, these grasshoppers can occasionally defoliate gardens plants and landscaping. However, these outbreaks are temporary, and the numbers drop quickly in 3-4 weeks, as the grasshoppers become food for predators such as birds, mammals, reptiles and predatory arthropods.

Management suggestion: If necessary, use non-toxic methods like using row covers, handpicking, or installing traps for small gardens, rather than chemical insecticides which can harm beneficials in the environment.

If you notice a lot of grasshoppers in your environment, take a few moments to enjoy these fascinating creatures while they are around.

What the Heck Was This?
(From our February issue)

         

Answer: Crane Fly.

Congratulations to Master Weed Detectives:

Donna Lorch, Maricopa Co. Master Gardener
Brad Kard 

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What the Heck is This?

  
 Identify this insect.

If you know the answer, email Shaku at nairs@arizona.edu. You will not win anything if you are correct, but you will be listed as a “Master Pest Detective” in the next newsletter issue.

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