Beetles on Milkweed Plants at Griggstown

When I was at Griggstown yesterday, I noticed a lot of beetles active around the many milkweed plants. The most obvious were the Red Milkweed Beetles (Tetraopes tetrophthalmus), present on seemingly every milkweed I checked. Some seemed to be foraging, but a lot of them were mating. This species is among the few that are able to feed on milkweed leaves (Asclepias sp.). Like other species that feed on milkweed, these beetles advertise their distastefulness (derived from the milkweed's chemicals) with their bright red color.

From this angle, you can see the reason for the beetle's species name, tetrophthalmus, which means "four eyes" in Greek. This species has four eyes, two above the antennae and two below the antennae. Most long-horned beetles have their antennae very close to their eyes. In the case of this species, the antennae split the normal two eyes into four.

While only a few species can eat milkweed leaves, many can feed on its nectar. One insect I noticed at the plant's flowers was this firefly. This one was rather large and is probably in the genus Photuris. According to BugGuide, the species in this genus are only distinguishable by flash pattern.

Near the firefly, I noticed this long-bodied beetle. Like the Pennsylvania Leatherwings I sometimes see around home, this is a soldier beetle. In this case the species is Margined Leatherwing (Chauliognathus marginatus). Adults of this species are active in early summer and often feed on pollen and nectar.

The last of the beetles is a Dogbane Beetle (Chrysochus auratus). Beetles of this species feed exclusively on plants in the dogbane family: larvae feed on the roots and adults on the leaves. This individual is perched on a milkweed leaf.

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