Sunday, February 25, 2007

Caterpillar Cages

Anybody can visit and buy a cage, but most of us have the materials to make a cage at home. Here is one method. This is simply a gallon jar with netting on top held on with a rubber band, a paper towel in the bottom to make frass (poop) clean up easy, and a small vase with foodplant (nasturtium in this case). A fish bowl could also be used. The insects don't really need much air, so a paper towel can be used on top instead of netting. Sometimes the larvae crawl into the water and drown, so it is nice to cover the vase with a bit of saran wrap and poke holes in it to put the plant stems through. I used a pretty vase, but an old spice bottle will do. The main concern, however, is fresh host plant. Take a vase with water with you when collecting more food plant, and put the stems in water directly after cutting them. The caterpillar depends upon the plant for food and water, so it must be fresh.

Another easy cage can be made out of an old Easter basket and netting. I get netting at Long's Drug Store, but any fabric store will have it. Again, put a paper towel in the bottom to catch the frass. Then put in a vase with foodplant. And last, use ribbon or string to tie the netting to the basket. Very simple and very effective. I like this cage because the caterpillars tend to pupate on the handle. The butterflies can cling easily to the handle when they emerge, and I don't have to worry about them falling. With the gallon jar, the caterpillars can cling to the glass and sometimes form the chrysalis on the glass. But since the butterflies can't cling to the glass, they sometimes fall and are unable to expand their wings. I tape long strips of paper towel next to the chrysalids on the glass to remedy this situation, but the basket seems like a better solution.

A tomato cage and one gallon nusery pot make the framework for this cage. If the foodplant is growing in the pot, that is best, but it also easy to put dirt in the pot and put a vase with foodplant on the dirt. Insert the legs of the tomato cage into the soil and cover with netting. The netting is overlapped and tied to the pot at the bottom and tied shut at the top. No paper tower to catch frass is necessary with this cage, the poop just falls into the dirt. If you want to get fancy, sew the netting into a tube before using it to cover the tomato cage. This cage works best for tall foodplants, like fennel.

No matter what cage you use, I recommend uncovering the caterpillars regularly to get a good look at them because it can be hard to see all their markings through the netting or the glass. So take down the barriers and enjoy the beauty of metamorphosis every day.

Sunday, February 18, 2007


When I look outside, it looks like spring! The sun is shining, everything is in bloom. Cherry trees! Violets! Daphnne! Sour grass! Acacia! Daffodils! It is the best time of year in Berkeley. The days are getting longer and everything is colorful: pink and white, yellow and purple, and of course very green from the rain. Pictured above is the aristolochia (pipevine) which blooms before it gets leaves. Those maroon flowers look like dead meat to the flies which pollinate it. The butterflies don't like the flowers much, but pipevine swallotails lay their eggs on it. I haven't had any in my yard, where these plants are, but hope springs eternal. Maybe this year I will have a colony.
It may be spring for the plants, but in the insect world, it is the dead of winter. I have no caterpillars in the house, the last gulf fritillary pupated a couple of weeks ago. No eggs or caterpillars outside. It is very difficult to find specimens this time of year. But I have seen a few adults flying the past couple of weeks. A cabbage white was in my yard yesterday. A California tortiseshell graced a sign on Telegraph avenue the day before. Mourning cloaks have been flying at the UC Bot garden. So I suppose the butterfly spring will be starting soon, although in past years it always seems like it took months between the first flight and first egg laying. I am looking forward to the next crop of caterpillars. I am going to need them for my classroom presentations.