Saturday, September 10, 2011

New Tobacco Hornworms

Pacific Science Center’s Life Sciences team is always looking for new species to add to our collection. Recently, we tried out some tobacco hornworms (Manduca sexta, also called hawkmoths, sphinx moths or hummingbird moths in the adult stage) to see whether we could rear them, and whether they would be of interest on exhibit. The results were quite successful.
The Tropical Butterfly House has done a wonderful job for the last 12 years of displaying chrysalids and adult butterflies. However, our USDA permits are strict about not allowing caterpillars inside the exhibit space. Anyone who has ever read, “The Very Hungry Caterpillar” should understand that caterpillars eat a lot of food, and produce a lot of waste. They can also be a vector of butterfly diseases or parasites that could potentially harm native species if they were to get out of the butterfly house. Since the USDA does not regulate hornworms, we were able to raise the caterpillars in a separate, controlled environment (a cage), and then release the moths into the butterfly house. We were excited to see how they would do.
Our hornworms ate well and grew. We offered them potato, a relative of tobacco, which is their normal host plant. They loved it, and continued to grow. After they were finished growing, the hornworms pupated.
They looked much like other pupae we have seen, except for the large, handle-like proboscis that reaches across the head and thorax of the pupa. Manduca moths have a very long proboscis. They are powerful flyers, and have the unique ability to hover while probing their long proboscis deep into flowers to get the best nectar.
Hornworms normally live on the leaves of tobacco and related plants. When they pupate, they burrow into the soil below. We prepared “burrows” in a block of wood, so that they could feel secure but still be visible to our guests. Once the first moth emerged, we released it into the butterfly house where it made itself at home.
Our moth has proven long-lived and spectacular in flight. She even appears to be friendly. When we first released her into the butterfly house, she landed on a guest right away. According to the guest, she had found the pocket where he stored his cigarettes. This makes sense for a species that has “tobacco hornworm” as one common name. The scent may have reminded her of her host plant!
The Tropical Butterfly House will be closed for the next few weeks for our annual cleaning, but we will try to keep the hornworms on exhibit throughout the fall. If you come to see us, look for the bright green caterpillars on display in the Insect Village. Please be aware that the hawkmoths are sometimes hard to see inside the butterfly house. They are nocturnal, and are great at camouflaging during the day. Still, if you do happen to see one, it’s a wonderful and exciting treat.

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