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Fennel is a Mediterranean plant that has been introduced to the U.S. Over many years, it has naturalized in our area. Recently, I saw an anise swallowtail butterfly visiting my fennel (Foeniculum vulgare) so I went out and looked for eggs and babies. The babies look like bird droppings as they are black with a white strip through their middle. In this search and subsequent ones, I discovered many small bugs living in the fine leaves of the fennel.

I originally planted this fennel to attract butterflies. The anise swallowtail is a beautiful yellow and black butterfly that especially likes the nectar of lily-of-the-Nile (Agapanthus). A few years ago, I was raising four anise swallowtail larvae and suddenly all but one died. I continued to watch the survivor until, one day, a small larva hatched out of his side. Then the caterpillar died.

I decided to observe what the larva turned into when it hatched. It was a small parasitic fly, and it had laid the egg before I had collected the caterpillars.

Butterflies of all species have a rough time laying eggs and raising them to full-size adults. That’s why I take the time every summer to raise as many larvae as I can in my house. As soon as they pupate, or hatch, I let them pump up their wings and leave.

As I worked my way around the fennel, I found two tiny black-and-white spiders. Each one had created a web, and as soon as the spider caught an insect, the insect was carefully wrapped in the web and stored for the future. Both of these guys stayed close to their catch to guard it. They left only to gather more insects.

The one bug that puzzled me was an almost-yellow stink bug. Although I am always watching bugs, this one was completely new to me. Over several days, I observed him. He moved to my milkweed plants, which concerned me, so I captured him in a jar.

I was finally able to identify him as a red-shouldered stink bug (Thyanta pallidovirens). He is considered a good bug compared to the brown marmorated stink bug (Halyo morpha halys). The latter damages plants while the red-shouldered stink bug eats other bugs. Both have a straw-like mouth, but the brown bug carries his down his stomach and the red-shouldered bug has his in front. I did see him sucking on a dead bug but that wasn’t what he really wanted.

As my fennel is finally preparing to bloom, there are many small flies and wasps visiting the buds. And the caterpillars are growing. In fact, one has already left the pupa and is hopefully laying more eggs.

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To raise them in the house, I put them when they are small into a small container. When they hatch, they are about 1/8-inch long. I add more fennel daily and clean out their droppings. After shedding and eating their skin four times, they turn orange and black. By that time, they have tripled in size. (This is true for all butterflies in the swallowtail family.) This amazing rate of growth is the reason they shed their skin.

After turning color, they eat without stopping. I have to transfer them to a larger container and clean their droppings twice a day. By that time, all that remains of the fennel is stubs.

Before they form a pupa, they go on a walk around the container. Once they settle down, it is a few hours before the skin covering opens for the last time. Underneath is the pupa. This will be their home for weeks or even months. Most will overwinter in their pupa and emerge the following spring to begin the process over again.

Workshop: UC Master Gardeners of Napa County will conduct a workshop on “Growing Olives” on Saturday, July 22, from 9:30-11:30 a.m., at Big Dog Ranch, 1020 Congress Valley Road, Napa. Got an olive tree? Want to grow one? Learn the details for each season’s necessary activity for a healthy and tasty harvest. Controlling olive pests is also on the agenda. Online registration (credit card only);

Mail-in registration (check only or drop off cash payment).

UC Master Gardeners of Napa County ( answer gardening questions on Monday, Wednesday and Friday, 9 a.m. to noon, at the UC Cooperative Extension office, 1710 Soscol Ave., Suite 4, Napa, 707-253-4143.