Beetle Update – Blog Post 4

At the beginning of last week, I was ready to begin introducing the longhorned milkweed beetle larvae to the experimental common milkweed plants. I first completed a destructive harvest of thirty experimental plants. I bagged the aboveground and belowground tissues for each plant and then placed them in a drying oven so that I will be able to later weigh the tissues. I will use these weights to construct a model of how belowground biomass and aboveground biomass relate to each other. On Tuesday morning, I was ready to begin removing the larvae from the kiddy pool where they had been feeding on the small (25-35 cm tall) milkweed plants. I looked for larvae for about 3 hours and very sadly found none. I removed all the plants from the kiddy pool and examined their roots in the greenhouse with an optivisor before bringing the roots down to the lab to look at them under the dissecting scope. I saw a few really tiny clear worms and a few really tiny shiny bugs under the dissecting scope, but that was it.

These findings felt very strange to me. I added thousands of eggs to the kiddy pool, but I did not even see any dead larvae. I started pulling apart the roots and discovered more tiny bugs inside some of them but no larvae. I added twenty-eight larvae directly to the pool the previous week, so I was expecting to at least see those. After examining all the roots of the plants, I went through the soil in the kiddy pool and found two larvae on my first pass through the soil. I was so shocked I combed through the pool again, but I didn’t find any more larvae during my second pass through the pool. The larger larva measured 7 mm and the smaller one measured 5 mm. Since I need more than two larvae for my experiment, I had to switch to plan B. We went back to Blandy Experimental Farm and collected more beetles. While they mate and their eggs develop over the next week, I will reexamine our methods for raising the beetles and see where something might have gone wrong.

The larvae from the kiddy pool



  1. jelandrum says:

    After rereading your blog post, I was able to grasp more on the work you are doing as someone completely out of their element. But, I now have a couple questions…What is a destructive harvest? And, what is the goal of the research you are conducting? Aside from my confusion, it sounds like you are doing great work and being proactive by having a plan B, which is always good. I hope you’re able to answer my questions and find a method that’ll provide more useful for recovering (or producing) the larvae. Good luck!

  2. mrdonnan says:

    A destructive harvest involves removing the entire plant from its pot and then separating the aboveground and belowground tissue. The goal of my experiment is to explore the effects of longhored milkweed beetle root feeding on re-sprouting in common milkweed. This first destructive harvest will give us an idea of how belowground biomass and aboveground biomass relate to each other at the beginning of the experiment. We will complete a second destructive harvest to see the relationship between the biomasses at the end of the experiment.

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