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Ten-lined June beetle

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Ten-lined June beetle
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Polyphaga
Infraorder: Scarabaeiformia
Family: Scarabaeidae
Genus: Polyphylla
Species:
P. decemlineata
Binomial name
Polyphylla decemlineata
(Say, 1823)

The ten-lined June beetle (Polyphylla decemlineata), also known as the watermelon beetle, is a scarab beetle found in the western United States and Canada. The ten-lined June beetle is most commonly found in the Pacific Northwest region (PNW) but are also spread throughout other parts of the United States (US) such as Colorado or Kansas[1]. They are known as a very common species of beetle[2]. The adults are attracted to light and feed on foliage while the larva feed upon roots of fruit-bearing trees. They can make a hissing sound when touched or otherwise disturbed, which can resemble the hissing of a bat. This sound is made by their wings pushing down, forcing the air out between their wings and back. They can be an agricultural pest affecting a wide range of crops because their larvae feed on plant roots and can weaken or kill the plants.[3]

Description

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They are relatively large in size, some growing to sizes as large as 1.5 inches (3 cm) or more. As in other members of this genus, the males have large distinctive antennae consisting of several lamellate plates, which they close up when threatened. The antennae are used to detect pheromones emitted by the females.[4] The wing covers (elytra) have four long white stripes and one short stripe each. Said short stripe appears to look like the other eight stripes until the elytra open up, revealing the line to be two, smaller lines rather than one large line. The underside of the thorax is covered with brownish hairs.

These insects are usually active from the early hours of dusk to around midnight or so[5]. Ten-lined June beetles are commonly attracted to lights. This can be attributed to their poor eyesight. While they are attracted to lights, this is their downfall since it highlights them for predators and allows them to fall into traps laid out by humans such as blacklight traps[6].

These beetles are commonly found within forests, shrublands, and farmlands. Due to the food sources that come from farms, the denser populations of these beetles are more commonly found within states that have larger farming population such as Washington and California. They appear to thrive in more sandy soils that are West of the Rocky Mountains[7]. While they are found all over the United States, their range is limited to the Northern and Western United States and Canada[8].

Outside of common predators such as birds, tachinid flies commonly parasitize these beetles. This however is not a significant threat to these beetles unlike other, larger predators[9]. Larva will however be parasitized by large tiphiid wasps which prove to be a larger threat to the beetles than the tachinid flies. Birds will commonly only feast upon the larva of the ten-lined June beetle while owls and bats will consume the adults[10]. This is why the beetle has a hissing mechanism while is used to mimic the sounds that bats make[11]. It is not recommended that humans consume these beetles since consuming too many can lead to gastrointestinal issues including, but not limited to, diarrhea[12].

Diet

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The ten-lined June beetle is known to be a pest to gardeners. These beetles commonly eat apple trees and other fruit based trees as well[13]. Their larva consume tree roots which can lead to either death or stunting of the tree. This damage is widely unnoticed until the tree topples over and dies. Since the grubs live underground for 2-3 years, this leads to the trees having little to no time to recover on a season to season basis. The way to remove these beetles from a garden is to remove the affected tree(s) and those around them, even if they are not ailed. Through this method, one can be sure they are rid of the beetles by removing the grub's food source[14]. While not an organic method, using phosphate-based insecticide can help deter the beetles as well. Adding this insecticide to the tree holes where the ten-lined June beetle larva were can aid in the removal process of these insects[15]. The adult beetles feed on leaves and fruit juices which makes them less of a pest than their larval counter parts[16].

Ten-lined June beetle, Coquitlam, July 26, 2017.

Identification

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This species is commonly confused with Polyphylla Critina, also known as the Long Haired June Beetle. Polyphylla Decemlineata, or the ten-lined June beetle, has scales on the protonum. The Long Haired June beetle (Polyphylla Critina) instead has setae (hair) on the protonum. Due to this difference, these species require high resolution photos for differentiation between the two.

Life cycle

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Eggs: The eggs are oval, dull, and creamy. They are about 1/16 of an inch long.[17] These are laid deep in the dirt by females to help avoid predations. Other insects will still feast upon these eggs, however, them being buried does reduce those chances from happening.

Larva: The grub can grow up to 2 inches (5cm) with 3 pairs of legs, with a white body and brown head. The larval stage can last as long as 4 years but usually lasts between 2-3 years. After the larval stage, the larva will go through three instars before transitioning over to the pupal stage the following spring[18]. These larva are commonly found8 or so inches underground which has led to many measures being taken against them proving ineffective[19]. During the pupal stage, the pupa is a creamy white and is around 1-1.5 inches in length. These pupas also possess external wing pads which will turn into their elytra when they mature[20].

The beetle will begin emerge from the ground early on in the summer (June) and will continue to emerge until July[21]. Once mature, the female ten-lined June beetle will release pheromones to attract a mate. After mating, the female beetle will return to the soil to lay her eggs while the male will depart to find another mate[22]. The adult life cycle of these beetles lasts only a short 10 months. While this may seem like a short time for a human, it is particularly long for a beetle of this genus[23].

  • Dorsal side ♀
    Dorsal side ♀
  • Ventral side ♀
    Ventral side ♀
  • Ten Lined June Beetle ♂
    Ten Lined June Beetle ♂
  • Ten Lined June Beetle - Open ♂
    Ten Lined June Beetle - Open ♂
  • Coming back to life after a cool night

References

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  1. ^ Coetzee, Chanel (2022-10-04). "Ten-Lined June Beetle". A-Z Animals. Retrieved 2025-06-24.
  2. ^ "Ten Lined June Beetle | Department of Entomology | Washington State University". Department of Entomology. Retrieved 2025-06-24.
  3. ^ "Tenlined June beetle". Orchard Pest Management Online. Washington State University Tree Fruit Research & Extension Center. Retrieved 26 June 2012.
  4. ^ Department of Entomology. "Ten Lined June Beetle". Washington State University. Retrieved 5 July 2013.
  5. ^ "Ten-Lined June Beetles". The Daily Garden. Retrieved 2025-06-24.
  6. ^ Coetzee, Chanel (2022-10-04). "Ten-Lined June Beetle". A-Z Animals. Retrieved 2025-06-24.
  7. ^ "Ten Lined June Beetle: Identification, Life Cycle, Damage, Treatment, FAQs". Exploring the Fascinating World of Insects - Entomologist.net. Retrieved 2025-06-24.
  8. ^ Coetzee, Chanel (2022-10-04). "Ten-Lined June Beetle". A-Z Animals. Retrieved 2025-06-24.
  9. ^ "Ten-Lined June Beetles". The Daily Garden. Retrieved 2025-06-24.
  10. ^ "Tenlined June Beetle | WSU Tree Fruit | Washington State University". Retrieved 2025-06-24.
  11. ^ Grimaldi, David (2024-10-18). "Do June Beetles Make Noise". Entomology Blog. Retrieved 2025-06-24.
  12. ^ Grimaldi, David (2024-06-06). "Are Ten Lined June Beetles Poisonous". Entomology Blog. Retrieved 2025-06-24.
  13. ^ "Ten-Lined June Beetles". The Daily Garden. Retrieved 2025-06-24.
  14. ^ "Tenlined June Beetle / Almond / Agriculture: Pest Management Guidelines / UC Statewide IPM Program (UC IPM)". ipm.ucanr.edu. Retrieved 2025-06-24.
  15. ^ "Ten-lined June Beetle". www.insectidentification.org. Retrieved 2025-06-24.
  16. ^ Coetzee, Chanel (2022-10-04). "Ten-Lined June Beetle". A-Z Animals. Retrieved 2025-06-24.
  17. ^ Department of Entomology. "Ten Lined June Beetle". Washington State University. Retrieved 4 July 2017.
  18. ^ staff (2021-03-13). "Ten-lined June Beetle: Identification, Life Cycle, Facts & Pictures". Beetle Identifications. Retrieved 2025-06-24.
  19. ^ "Tenlined June Beetle / Almond / Agriculture: Pest Management Guidelines / UC Statewide IPM Program (UC IPM)". ipm.ucanr.edu. Retrieved 2025-06-24.
  20. ^ "Ten Lined June Beetle: Identification, Life Cycle, Damage, Treatment, FAQs". Exploring the Fascinating World of Insects - Entomologist.net. Retrieved 2025-06-24.
  21. ^ "Ten Lined June Beetle | Department of Entomology | Washington State University". Department of Entomology. Retrieved 2025-06-24.
  22. ^ "Ten-Lined June Beetles". The Daily Garden. Retrieved 2025-06-24.
  23. ^ Coetzee, Chanel (2022-10-04). "Ten-Lined June Beetle". A-Z Animals. Retrieved 2025-06-24.
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