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Western yellowjacket

Western yellowjacket

Vespula pensylvanica

A species of Ground yellowjackets

The western yellowjacket (Vespula pensylvanica) is known for its painful stings. It often flies near areas with crowds of people and lots of food. These wasps will aggressively guard their nests, which is how many people get stung. Their round, paper-like nests are usually built on the ground, where they should be avoided at all costs.

Toxic to Humans
Toxic to Humans
Toxic to Animals
Toxic to Animals
Bite Animals
Bite Animals
Does the Western yellowjacket sting humans?
Human Stinging
General Info About Western yellowjacket
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Attributes of Western yellowjacket
Colors
Black
Yellow
Habitat
forest; prairie; urban zone; garden; parkland; meadow; house
Adult Food Sources
Nectar, fruit juices, insects, human food remnants, honeydew
Larva Food Source
Caterpillars, flies, beetles, aphids, spiders
Biting/stinging
The Western yellowjacket may bite humans actively. Please stay away from it.
Allergy-causing
Not reported
Defensive attack
The Western yellowjacket has special defensive behaviors that can trigger an allergic reaction. If there are serious reactions, seek IMMEDIATE medical attention.
Venomous
The Western yellowjacket can induce toxic reactions varying in severity. Nevertheless, these toxins primarily target their prey and predators and are usually not fatal to humans.
Non-poisonous
Not reported
Borer
Not reported
Biting animal or pet
Yes
Mouthparts Type
Chewing-lapping mouthparts
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Appearance of Western yellowjacket
The western yellowjacket shares the basic yellow and black pattern with other species of social wasps in the genus Vespula. Though both species have a similar diamond-shaped black mark on the first tergum, Vespula pensylvanica can usually be differentiated by the continuous yellow ring (often referred to as an eye-loop) present around each eye. The fore wing length ranges from 9 - 11 mm for workers, 1.3 - 1.5 cm for females, and 1.3 - 1.4 cm for males.
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How to Identify Western yellowjacket?

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Life Cycle of Western yellowjacket
Egg In the egg stage, western yellowjacket remains immobile, encapsulated in a protective shell. The eggs are usually oval and diminutive in size, with colors that may blend with the environment to avoid predation.
Larva As a larva, western yellowjacket is worm-like with a voracious appetite for feeding and growth. During this stage, it molts several times, increasing in size but generally retaining the same appearance.
Pupal The pupa stage of western yellowjacket is a transformative phase. Enclosed in a cocoon, it appears dormant but undergoes significant internal reorganization, resulting in drastic morphological changes.
Adult Emerging from the pupa, the adult western yellowjacket’s development is marked by the presence of wings and functional reproductive organs. The body is fully formed and hardened, and the adult is mobile, focusing on reproduction.
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Adult Size of Western yellowjacket
1.5 cm
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Predators of Western yellowjacket Larvae
Frogs, toads, birds, rodents, spiders, beetles, other predatory insects
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Predators of Adult Western yellowjacket
Birds, rodents, reptiles, mammals, spiders, praying mantises, dragonflies
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Interesting Facts About Western yellowjacket
The western yellowjacket can fly sideways and even upside-down momentarily when navigating obstacles or tight spaces.
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Scientific Classification of Western yellowjacket
Tips for Finding Western yellowjacket
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How Can You Attract Western yellowjacket
Meat or sweet foods like jam, fruit, or sugary beverages can attract western yellowjacket.
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Habitat Preferences of Western yellowjacket Through Different Life Stages
The larval stage of western yellowjacket is generally found in gray or brown papery nests located underground or occasionally above ground. These nests are often built in rodent burrows or similar cavities, where consistent humidity and temperatures are maintained. To find larvae, search for nests in open fields, gardens, and near human structures. The pupal stage occurs within the same nests, in individual cells made of chewed plant fibers. Adult western yellowjacket forage for food and are commonly seen around human activities, seeking sweets and proteins, often appearing in picnic areas, garbage bins, or outdoor food sources. Mature western yellowjacket are likely to be encountered on flowers and vegetation in the vicinity of the nests where they collect nectar.
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When is the Best Time to Observe Western yellowjacket
Late spring to early fall is the most active period for western yellowjacket, particularly on warm and sunny days.
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What is the Best Weather to Observe Western yellowjacket
Dry, warm, and sunny weather conditions are more suitable for finding western yellowjacket as they are less active during cold or rainy days.
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How and Where Can You Find Western yellowjacket at Different Life Stages
Larva Western yellowjacket larvae are found in the nest, usually in hidden places like underground or in hollow trees. Locate nests by observing the flight path of the adults.
Pupal Western yellowjacket pupae remain inside the nest within protective silk-capped cells. Finding the nest as mentioned in the larval stage gives access to pupae.
Adult Western yellowjacket adults can be found foraging for food. They are often attracted to gardens with flowers or areas where human food is present. Use sweet baits in traps to capture them outdoors.
Are Western yellowjacket harmful?
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The western yellowjacket can cause toxic reactions with a wide range of severity. However, the toxins are typically targeted at their prey and predators. They are usually not fatal to humans.

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Are Western yellowjacket harmful to humans?

The female wasp has a long thick stinger connected to the poison gland. The main components of the venom are some alkaline substances, including histamine, serotonin, bradykinin, hyaluronidase, etc. When it is stung, it will shoot venom into the skin of the person, but the sting needle is not left in the leather suit. After a person is stung by a wasp, the stinged skin will immediately become red, swollen and painful, even with petechiae and skin necrosis. When the eye is stung, it will cause severe pain, tearing, redness and swelling, and may also cause corneal ulcers. In addition, systemic symptoms include dizziness, headache, vomiting, abdominal pain, diarrhea, restlessness, and increased blood pressure. The above symptoms usually disappear within a few hours to several days. In severe cases, drowsiness, systemic edema, oliguria, coma, hemolysis, myocarditis, hepatitis, acute renal failure and shock. Some people allergic to bee venom can manifest as urticaria, anaphylactic shock, etc.
Harmful Effects of Western yellowjacket
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Toxic to Humans
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Toxic to Animals
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Bite Animals
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Toxic to Humans

Western yellowjacket possesses a sting used for defense, capable of injecting venom containing neurotoxins and immunotoxins, which can cause localized pain, swelling, and an inflammatory response. In general, the sting has a mild effect on humans, with symptoms usually subsiding without long-term consequences. However, repeated stings or envenomation in sensitive individuals may provoke more severe symptoms and complications.

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Toxic to Animals

Western yellowjacket is known to deploy its sting as a defense mechanism, dispersing toxins that range from mildly irritating to severely harmful. When western yellowjacket stings humans, it can cause varying reactions, from temporary discomfort to acute allergic responses. Smaller mammals like dogs and cats may also exhibit similar symptoms of distress when stung. Other animals within western yellowjacket's ecological reach can experience discomfort or harm, depending upon their size, physiology, and potential allergic sensitivity to the toxin.

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Bite Animals

The western yellowjacket has a propensity to bite when disturbed or threatened. While searching for food, they may also bite. Their mandibles are well-developed, allowing them to cut into flesh and grip their prey or attacker. This is done as a mechanism for feeding on insects or as a defense strategy.

More Effects of Western yellowjacket

Beneficial Effects of Western yellowjacket
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Pollinator
Predators of Pests
Pollinator
Pollination Behavior Reason
Eat Pollen Or Nectar
Western yellowjacket assists in pollination primarily while searching for food. Attracted by the vivid colors and enticing scents of flowers, they inadvertently collect pollen on their bodies. As they move from flower to flower, they accidentally transfer pollen, aiding in the reproductive process of plants.
Predators of Pests
Purpose
Feed Itself, Feed Offspring
Diets
Caterpillars, Flies
Western yellowjacket are remarkable predators that play a dual role in the ecosystem. They are known for hunting down various insects such as caterpillars, flies, and spiders to feed their larvae and themselves. Adult individuals catch prey to nourish their developing young, while larvae require substantial protein for growth. Even as adults, they continue to consume smaller pests, showcasing their lifelong predatory habits.
Common Questions People Also Ask
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