2012年2月3日星期五

How much food does a cabbage butterfly larvae eat in a day?

Caterpillars are eating machines - that's what they do, that's all they do. Cabbage butterfly (Pieris rapae) larvae (known as cabbageworms or imported cabbageworms) go through five instars in about 15 days. Each instar is a molt - the caterpillar sheds its skin for a larger one. The size of the five instars averages 3.2mm, 8.8mm, 14.0mm, 20.2mm, and 30.1mm, respectively. The 5th instar larva does the most feeding - perhaps more than all other life stages together.



These larvae are famous for producing gross quantities of fecal material, so they probably eat quite a bit compared to their body weight. But all of that crap may also mean that the leaves are not very nutritious, so they need to eat a lot to get what they need. If a caterpillar receives more or less nutrition at every meal, less or more foliage is required to kick in the hormones that trigger a molt to the next instar and finally pupation.



Cabbageworms feed on many plants, including cabbage, cauliflower, broccoli, Brussels sprouts, turnip, radish, kale, nasturtium, lettuce, collards, turnip greens, rutabaga, kohlrabi and mustard greens. Many of these plants, and their different cultivated varieties, produce waxy leaves or contain nasty chemicals to deter caterpillar feeding - there's a huge variety. So the answer to your question depends on what plant these caterpillars are eating - the host plant and the variety, if it's been bred. Confounding variables probably include average day and night temperature, perhaps the amount of rainfall, cultivation practices, fertilization, time of season, etc. So there'll be many different measures that answer this question. It's to be expected though - anything to do with life has huge variablitlity.



You need a literature search of entomological journals. Without doubt, researchers have reared larvae in the lab and measured the feeding of each instar on a variety of plants. Field data will be entirely different, of course. The databases that contain this information are pay sites, see, for example, the Entomological Society of America's Journal of Economic Entomogy, the Canadian Entomologist is good for this kind of thing too. You can also find these at a university biological sciences library.
How much food does a cabbage butterfly larvae eat in a day?
About four cabbage leaves in 15 days. This averages to just over 1/4 leaf per day.
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