Matthew Putnam, a UOG graduate student and research biologist at the UOG Center for Island Sustainability (CIS), recently made a breakthrough in captive rearing of the Mariana eight-spot butterfly, an endangered and listed species. CIS Associate Director for Natural Resources Dr. Else Demeulenaere has mentored Putnam in conservation biology for several years, and his thesis supervisor is Dr. G. Curt Fiedler, UOG College for Natural Appliance Sciences (CNAS) biology professor.
Putnam’s research on Hypolimnas octocula marianensis is an important contribution to the scant knowledge about this species endemic to the Marianas and the subject of his master’s thesis. These insects are dependent on two species of host plants for their life cycle: Procris pedunculata and Elatostema calcareum (tupon ayuyu). The common term used for butterfly in CHamoru is ababang. However, there is no specific CHamoru name for the Mariana eight-spot butterfly.
Little is known about the basic biology of this butterfly, so Putnam worked with Dr. Fiedler and Dr. Aubrey Moore, UOG CNAS research and extension entomologist, who hold the permit to collect and raise this species via a grant from the Guam Department of Agriculture. Before raising captive butterflies, Putnam spent a year monitoring butterfly sites in the wild at Andersen Air Force Base, as part of Dr. Fiedler’s endangered species monitoring project funded by NAVFAC Marianas.
In preparation for rearing, Putnam built a rearing tent in the CIS compound and furnished it with cages according to Dr. Moore’s recommendations. He also cultivated host plants in the CIS nursery for the hungry caterpillars. When the system was ready, Putnam and Fiedler collected eggs and caterpillars from a site near the UOG campus.
Captive caterpillars were fed cultivated Procris host plants, while adults were provided artificial nectar made of sugar, water, and sports drink.
“No one has trialed raising these butterflies and we definitely experienced a learning curve. Ants and lizards were a problem we had to overcome. One thing I observed was the larvae frequently fell off the host plant, another observation was the competition of so many caterpillars on one leaf, with the early hatchers out competing the later ones leading to malnutrition and deformed butterflies,” said Putnam. “We reared 38 adults out of 333 eggs with 90% survival rate from eggs, but a high number of losses with the larvae.”
Rearing efforts revealed some interesting results. “I observed that the eggs, which are light green, turn a translucent black the day before the caterpillar emerges. This was at first confusing, because more often than not, in the wild a black egg indicates a tiny wasp has parasitized it. Upon closer observation, however, the parasitized eggs
were rather solid black,” explained Putnam. These predatory wasps are one reason for the low numbers of eight-spot butterflies in the wild.
Thanks to this research, Putnam documented that some eight-spot larvae exhibit a red face capsule for a short time before it turns black. A black face capsule typically denotes Hypolimnas octocula and a red face capsule for Hypolimnas bolina.
Putnam found the life cycle of these butterflies is approximately 7 days from egg to larvae, 2-3 weeks for the larval stage (caterpillar), 7-11 days for the pupal stage (chrysalis). Prior to this study, it was unknown how long eight-spot butterflies live. Putnam monitored and recorded the life span of five of the captive-reared butterflies. Three different individuals lived for 18 days, 14 days, and 25 days each. There were two individuals that were longer lived. One survived for 46 days and the other for 74 days, which surprised everyone with its longevity.
This research has resulted in important information about the Marianas eight-spot butterfly for future scientists to draw from. Putnam, Fiedler, and Demeulenaere have a submitted a grant proposal via the Department of Agriculture for additional State Wildlife Conservation funds from the US Fish and Wildlife Service. In the meantime, NAVFAC Marianas has provided funding to Dr. Fiedler to support Putnam’s rearing efforts in the short term.
CNAS and CIS continue to support studies to increase the knowledge of our natural resources both flora and fauna.