Costa Rican Dung Beetle with Phoretic Mites

bugman

January 7th, 2009 at 10:04 pm

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digging beetle with parasites?
Tue, Jan 6, 2009 at 8:06 PM
The beetle pictured is quite large and heavy. It is common during certain months in Coto Brus which is about 1100 meters altitude on the Pacific slopes of Talamanca Mts. in southern Costa Rica. This one was on its back and was apparently infested with what look like ticks. I didn’t know ticks parasitised insects. Could you please confirm both the name of the beetle and the creatures in ventral view that appear to be parasites? Third try.
Mary Thorman
highland rainforest sw Costa Rica

Dung Beetle

Hi Mary,
Thanks for your persistence. Sadly, we just don’t have time to answer all the letters that we receive. This is some type of Scarab Beetle, probably one of the Dung Beetles. The parasites are Mites. Many Mites are parasitic, but there are also Mites that use flying insects for transportation. These opportunistic Mites often nearly cover certain beetles, most notably Burying Beetles. In the case of the Burying Beetles, the Mites feed on Maggots that infest the carrion that the Burying Beetles lay their eggs upon. That is a symbiotic relationship. The Mites are transported to a new food supply, and the progeny of the Burying Beetles don’t have to compete with the Maggots for a food supply. If this is a Dung Beetle as we suspect, the mites may be using the beetle for transportation, but we suspect, because of their location, that they may be parasitic. We would really need an expert opinion on this matter.

Dung Beetle with Mites: Passengers

Letter from the previous day with additional information
Mon, Jan 5, 2009 at 8:14 PM parasitic arthropods on beetle
Hi, again! I thought I had sent pictures of this large beetle with what appear to be parasites infesting it. Are the smaller “bugs” on the ventral surface of the beetle ticks? They are very tiny, but . . . kind of icky. And can you help me identify the beetle. They are common during certain times of the year here in the highland rainforests of Costa Rica. They are attracted to lights at night and often bash into window with a loud “bam!” If I go outside I can collect a few to feed to my coatimundi the next day.
Mary Thorman
1100 – 1200 meters altitude, southwestern Costa Rica

Update: From Eric Eaton
Daniel:
The Costa Rican dung beetle is probably in the genus Dichotomius (we have at least one species in the U.S.). Those are indeed phoretic (hitchhiking) mites on it.
Eric

Update: Costa Rican Dung Beetle with Phoretic Mites
Fri, Jan 9, 2009 at 11:58 AM
Hi Daniel:
Further to Eric’s comments, there are several species of Dichotomius in Costa Rica; D. annae appears to be a very close match. A brown coloration in the posterior portion of the striations on the elytra is characteristic of the species. This feature seems evident in Mary’s photo, although it looks confusingly like the dirt on other parts of the beetle. Regards.
Karl