Male Hawaiian yellow-faced bee, Hylaeus anthracinus. Photo by Sheldon Plentovich/USFWS

Endangered Hawaiian Yellow-Faced Bees Threatened by Invasive Ants

By: Ivan Vicente, Public Affairs Officer, U.S. Fish and Wildlife Service

The endangered Hawaiian yellow-faced bee, (Hylaeus anthracinus) is being threatened by invasive ants — a recently quantified discovery by researchers with the DLNR Division of Forestry and Wildlife (DOFAW) and the U.S. Fish and Wildlife Service’s Pacific Islands Coastal Program (USFWS).

Invasive species such as ants have adverse, often catastrophic impacts on Hawaiian ecosystems and wildlife, including native insects like Hawaiian yellow-faced bees. This happens by way of direct predation and indirectly via competition. The USFWS Pacific Islands Coastal Program and DLNR are working collaboratively to understand the factors contributing to species declines and develop solutions to stabilize and recover these unique species.

Female yellow-faced bee on ‘Akoko with two invasive glaber ants (Ochetellus glaber) which kill larval (i.e., baby) yellow-faced bees in their nests and eat the same food as yellow-faced bees (flower pollen and nectar). Photo by Sheldon Plentovich/USFWS

The importance of saving these insects is crucial as less than 5% of insects in Hawaiian coastal areas are native to the islands. Hawaiian yellow-faced bees are one of a very few native insects that survive in lowland areas in the main Hawaiian Islands. Though once abundant in coastal areas, this Hawaiian yellow-faced bee (Hylaeus anthracinus) persists in healthy populations in only a few areas on O’ahu. The majority of the 63 known species of Hawaiian yellow-faced bees have experienced significant declines in range and population and many have not been seen in recent years. In 2016, seven species received federal protection under the Endangered Species Act of 1973.

The collaboration between USFWS Pacific Islands Coastal Program and DOFAW evaluated the effects of invasive ants on nesting Hawaiian yellow-faced bees using artificial nest blocks that allowed researchers to observe and track nest construction and development. The blocks are made from pieces of 2’x 4’ and holes were drilled in each to match dimensions the bees are known to use.

Nesting blocks, one that allows ants access and the other prevents ants from access, used to study the effects of ants on nesting Hawaiian yellow-faced bees. The block on the left has a sticky resin on the rope to prevent ants from accessing it. The block on the right is our experimental control and ants are able to access it normally. Photo by Sheldon Plentovich/USFWS

The wooden blocks were placed in pairs at 22 points, encompassing three sites on the north and east sides of O’ahu. One block in each pair was treated with a sticky barrier (akin to petroleum jelly) to prevent access by ants while the second block remained untreated.

Yellow crazy ants (Anoplolepis gracilipes) investigate a nesting block. This highly invasive and harmful species not only prevented nesting by Hawaiian yellow-faced bees but seemed to prevent foraging by adults as well. No adults or nests were found in areas that had been invaded by yellow-crazy ants. Photo by Sheldon Plentovich/USFWS

It was discovered that 70% of nests in untreated or “control” blocks were invaded by ants. Nests in treated blocks (protected from ants) were more likely to produce at least one adult than nests in untreated blocks (with no barrier).

Hawaiian yellow-faced bee nest under construction with the female still present. The female has constructed 3 cells so far, each with an egg and pollen provisions for the larvae. Photo by Sheldon Plentovich/USFWS

Cynthia King, DOFAW’s State Entomologist said, “In addition to habitat loss, invasive ants are suspected of causing range reductions and population declines, especially in coastal areas where ants are more abundant. The negative impacts of invasive ants are also amplified across native ecosystems, because the loss of native pollinators can also result in the loss of unique native plant species.”

“Invasive ants are one of a multitude of threats this species faces. You can help protect our native bees by protecting coastal vegetation and staying on trails, keeping motorized vehicles off the vegetation, and not using coastal vegetation and coral rubble for fires or fire pits — they may contain yellow-faced bee nests,” said Sheldon Plentovich, USFWS Pacific Islands Coastal Program Coordinator. “There are ongoing opportunities to get involved and help the bees by volunteering with invasive species control programs and coastal restoration projects. Hawaiian yellow-faced bees are Hawaii’s only native bees and it is important we work together to protect them.”

The invasive glaber ant, Ochetellus glaber, depredates the nest of a Hawaiian yellow-faced bee in one of our nesting blocks. These ants entered nests and ate the eggs, larvae and/or pupae of 70% of nests that were not protected from ants. Video by Sheldon Plentovich/USFWS

The U.S. Fish and Wildlife Service works with others to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people. For more information, connect with us through any of these social media channels at https://www.facebook.com/PacificIslandsFWS, www.flickr.com/photos/usfwspacific/, or www.twitter.com/USFWSPacific.