Frass tubes and ambrosia beetles, Stone Zoo

[urbpan]

I was checking a stable fly trap (hold that thought) over by the wolf exhibit at Stone Zoo when I noticed this dying tree festooned with little growths!



They seemed so evenly spaced and equal in size that it was hard to imagine that they were made by an animal. I was sure I hadn't seen anything like this in Tracks & Sign of Insects & Other Invertebrates


Of course I was wrong. When I went to the section on wood-boring insects sure enough I found a photograph of a similar phenomenon. What we're seeing is the compacted chewed wood and frass (insect droppings) being extruded behind the activity of the larva of an ambrosia beetle (subfamily Scolytinae). In some species the mother beetle seeds the wood with fungus spores when she lays her eggs so the larva can feed on nice wholesome mycelium instead of troublesome wood cellulose.


One of the bore hole sites was clean of frass--the diameter of the hole is about 2 cm. I'm tempted to do what Charley Eiseman, one of the authors of the above book, does: he'll take a sample of the plant being infested and keep it until the larva pupates. Adult insects are usually much easier to identify than larvae.

Comments

[urb-banal.livejournal.com]

We have a rash of Emerald Ash borer. It leaves a distinctive "D" shape hole. The Ash first looses the top leaves and then starts desperately producing seeds and off shoots at the base. We will loose 20% of our urban canopy by the end of it. Stupidly, Toronto planted Ash trees exclusively along several streets.