#Caterpillar green with black stripes free

Concerned, we separated the dark caterpillars from the normal ones and raised them in the same area, same shelves, but in a totally separate rearing container. These caterpillars were found in the same containers, with the same food, same amount of light, and same temperatures as those that were normal colored. It was as if someone had colored them with water color and the black paint bled into the yellow paint. There wasn’t a clear clean line between the black and yellow bands on the caterpillars. Those few dozen had black lines that were wider and messy. Over a period of several weeks, we saw dozens more as we raised roughly ten thousand Monarchs. Even though they can often emerge and fly fine, they have serious health issues.One week we saw, out of the thousands of caterpillars in the labs, several dozen dark black Monarch caterpillars. These Monarch caterpillars are abnormally dark. A disease or parasite can cause the gut wall to be breached and gut bacteria to enter the hemolymph of the caterpillar, resulting in bacterial infection. In the photo above, two caterpillars are side by side. If bacteria is in the hemolymph, it will cause the caterpillar to appear dusky/dark. At the bottom of its heart, holes draw hemolymph into the heart and it is pumped back up to its head area again. Hemolymph is pumped out of the heart at the head of the caterpillar and flows freely though its body to the rear of the caterpillar. The dark line down the back of the caterpillar is its heart.

#Caterpillar green with black stripes free

Their hemolymph is free flowing in their bodies. They do not have blood vessels as do many animals. Bacteria will sometimes enter the hemolymph/blood of a caterpillar. The bright white is not present on their bodies as you see with healthy caterpillars.

Left: healthy Right: bacterial infectionīacterial infection as well as other diseases sometimes cause the caterpillar’s white bands to become dusky. In a rearing container, the vast difference in level of light won’t be present to cause the difference in band width. They are colored differently simply because they were in different light although they were on the same plant in the same area. If they are collected from the same garden, from the top of the same plant, in bright sun, their white bands will be wider. If they are collected from a garden, some from the bottom of leaves on the lower part of a wide-leafed milkweed plant, their black bands will be wider. All of these caterpillars are healthy.Ĭaterpillars raised together in the same rearing container should be the same basic color. The darker ones were raised in a closed lab in rearing containers with very little light. The lighter caterpillars were outdoors on plants that had very few leaves left to protect them from the sun. The photo above shows normal color variation that is caused by the amount of light in which the caterpillar has been living.