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Beginners Guide to Beetle Description Part 3

When I told my fiancée about my beetle collecting hobby, I did not expect her to enjoy it as much as she did. She relayed the news to her family members and friends. I fully expected them to think I was weird, but surprisingly they fully embraced it. Now everyone sends me pictures of beetles they want me to identify. The specimen I am using for part 3 of my description series came from my fiancée’s uncle, who works on a farm in Williams, California. He was very excited to show me what he had found for me. When I saw it, I too was thrilled because I did not have this specimen yet. It was the Ten-Lined June Beetle (Polyphylla decemlineata). The first thing I noticed about this beetle was its size. It was an inch and a half long. It was yellowish-brown in color, with ten white lines on its elytra and three white stripes on the pronotum. It was bristled (setose) along its dorsal, setose between all of its joints to protect from intruders, and had longer blond hairs sticking out from its sternum that trailed onto its legs (Figure 1).


Fig. 1. The picture shows Polyphylla decemlineata and its defined features. Photo by N.Morrison/MYOPS

The following is the taxonomic classification of Polyphylla decemlineata:

  • Domain - Eukarya or a cell with a true nucleus

  • Kingdom - Animalia

  • Phylum - Arthropoda or an invertebrate with a segmented body and jointed limbs

  • Class - Insect

  • Order – Coleoptera or sheathed wings

  • Suborder – Polyphaga (sternite not divided by coxa)

  • Family – Scarabaeidae

  • Genus – Polyphylla

  • Species – decemlineata

Other additional features are the oval body shape, moderately sized triangle-shaped scutellum, spikey (scalloped) tibia, a head smaller than the prothorax, and a prothorax that is slightly smaller than the abdomen. The shield-like structure (clypeus) above its mouthparts is also representative of the Scarab family. Since it is part of the scarab family, we can also expect it to have the Tarsal formula of 5-5-5 (Figure 2). That means feet (tarsi) with five segments in the front, hind, and rear.


Fig. 2. The picture shows the beetle’s tarsal formula 5-5-5, which is characteristic of the Scarab family. Photo by N.Morrison/MYOPS

This California native appears in June, as its name suggests, and flies around looking for a mate. The specimen we have is female based on its small lamellate antennae (Figure 3).



Fig. 3. The picture shows the lamellate antennae of the female Ten-Lined June Beetle. Photo by N.Morrison/MYOPS

The female will lay in wait for a male that has giant lamellate antennae to come and mate. The male’s antennae are so large that they remind me of antlers. I am hoping to add a male to my collection eventually to make a pair. Thank you so much for following along as I continue to make progress in my description series, where I get to talk about some of my favorite insects.


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