Beetle Symbioses

I just got back from leading the SEAK (Students Excitedly Seeking Knowledge) trip in the BWCA. We spent 5 days and 4 nights camped out on an island on Homer Lake. Every day we canoed around and explored a little, although much of that time was spent sheltering from the rain. At the entry point and while setting up camp on the first day I noticed a lot of white spotted pine sawyer beetles (Monochamus scutellatus). They are quite impressive with their long antenna and strong looking mouth parts. Many of these beetles were hosting some symbiotic mites. It's hard to say what that symbiotic relationship is though, based on this paper there are a lot of potentials of what species(s) of mites these were. They could have been parasitic, mutualistic, or commensalistic. It seems most likely they have a life style know as phoresy, a short-term commensalism where one species is transported by another, a common phenomenon seen amongst mites and beetles. At night as I was trying to fall asleep I heard a cacophony of buzzing mosquitoes, croaking frogs, and perhaps the loudest of all, sawyer beetle larva. Our tent was right next to a large, dead white pine. The larva of this species eats the inner wood of dead conifers, as they chew it sounds almost as if someone is cutting into the tree with a saw, hence the name. It was pretty cool to hear that many larva cheing away, but also made it difficult to sleep. 

White spotted pine sawyer beetle (Monochamus scutellatus)

Our canoes were under a dead white pine, they got lots of beetles on them

Almost every beetle had some amount of mites on them 

My phone was dead when I saw it, but I also came across a tomentose burying beetle (Nicrophorus tomentosus) with mites on it. These ones belong to the genus Poecilochirus in the P. carabi species complex, known as the carrion beetle mites. These are mostly a phoretic species that rely on beetles to transport them from one carcass to another, where they consume fly larva.

Tomentose burying beetle (Nicrophorus tomentosus) with Poecilochirus mites, photo taken last fall

I saw plenty other beetles, only some I was interested in enough for a picture. 

Eastern aspen stag beetle (Platycerus depressus)

Bee-mimic beetle (Trichiotinus assimilis)

While exploring a shallow stream leading into the lake I also learned about an entirely unknown (to me) phylum, now that doesn't happen every day. The bryozoans are simple aquatic invertebrates. Colonies are composed of many zooids which have tentacles that they use to filter feed. The zooids seek shelter in an unmineralized, gelatinous secretion. They are seemingly very similar to corals, although distantly related. 

A bryozoan, Cristatella mucedo seems like the most likely candidate

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