Tuesday, November 13, 2007

3. Copal Resin and the Resin Weevils

Written December 2006 (translated from Spanish original)

One of my main jobs as the manager of the Center for Amazon Ecology copal resin project is to carry out monthly monitoring of copal trees in the Jenaro Herrera Center for Investigation run by the Institute for Investigation of the Peruvian Amazon (IIAP). Our first group of study trees are located in the Arboretum and two areas of copal tree plantations (that we call Plantation 1 and 2). By the end of December 2006, we had also marked 102 copal study trees in natural forest just north of one plantation (that we call North Forest). One principal goal of my mission is to photograph the resin lumps on the outside of these trees.

The action of a weevil, a member of the beetle (Coleoptera) family, is normally responsible for the formation of resin lumps on these trees. The process starts when a female places its egg inside the bark. When the larva hatches, it eats the inside bark and provokes the flow of liquid resin onto the outer bark. This resin hardens when it is exposed to the air. The lumps are small at first and then grow along with the growth of th
e larva. I take photos of the same lumps every month and send them to Dr. Plowden. He uses Photoshop to measure the lump sizes to estimate the growth of the lump and the larva inside.

Photo: Resin lump made by a weevil larva. © C. Plowden/CACE

We completely cover some of the resin lumps with a cone-shaped wire mesh trap. We designed this trap to capture an adult weevil when it emerges from the resin lump. This will allow us to measure the stages of the biological cycle of this insect. I check these traps every month to look for any newly emerged resin weevils.

Photo: Angel installing a cone mesh trap. © C. Plowden/CACE

We have also placed small plastic traps near resin lumps on some trees to try and catch and learn about weevils and other insects that live in these trees that can be later identified. We have so far trapped five kinds of beetles. We now need to know which of them make the resin lumps.
Photo: Adult weevil found near a resin lump on a copal tree at Jenaro Herrera. © C. Plowden/CACE

In the forest, there are also stingless bees that interact with the copal trees by collecting their resin. During these months we have trapped many types of bees and a wasp. We'll report more about these later.

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