Silk Moth Blog

The Polyphemus moths have begun to emerge from their cocoons - 7 females and 2 males emerge in one day. I put the females into 3 separate mating boxes and leave them by an open window so that they can release their pheromones. By 1 am, they have called in a couple of male moths. I mate two of the females with wild males.

I release all the moths except one of the pregnant Polyphemus moths which I keep in a paper bag to lay her eggs.

The female Polyphemus has laid a total of 103 eggs. Half of these eggs are now in the Ecology Lab under modified temperature and humidity conditions. As a control measure, the other half of the eggs have been placed in a natural area, their habitat was not modified in any way so that they are subject to natural conditions.

A total of 10 males and 1 female Cecropia Moths have emerged, which is a stark contrast to the sex ratio of the Polyphemus moths. I will attempt to mate the female tonight using the same method as the Polyphemus moths. I will also be releasing the males tonight, but I have tagged them with small stickers to prevent inbreeding should they find their way back to the female through her pheromones.

Successfully mated a Cecropia moth at 2:40am on June16th, and over the next 2 days she laid 153 eggs into a paper bag. However, she presented odd behaviour while laying eggs, and laid thick bundles of 10-20 eggs on her legs rather than on the bag. Usually a female will lay groups of 3 eggs randomly, and never on her own body. I removed them from her and pulled apart the eggs before the substrate used to stick eggs to leaves completely dried. However I do not know if I have accidentally damaged any eggs in the process, despite my carefulness. This will be interesting to observe once the caterpillars begin to hatch in 10-14 days.

Approximately 15 caterpillars from the Polyphemus moth have begun to emerge after 10 days!

The caterpillars are tiny, approximately 0.5 cm in length. I will wait until tomorrow when more caterpillars have emerged in order to get the true mean length and weight of the newly hatched larvae.

A total of 48 caterpillars have survived, with only 1 egg unsuccessfully hatched and 2 deaths. We weighed and measured the day old caterpillars today, with each caterpillar having an average weight of 7.8 milligrams and an average length of 0.5 cm.

The caterpillars have grown to 1 cm long, and some of the larger ones are showing signs of molting. When caterpillars are ready to shed their skin and enter the next instar, their face place becomes shrunken and they do not move for 1-2 days. We will have to be careful not to disturb the caterpillars once they have begun to molt.

There are still no hatchings from the tank in the natural area.

Polyphemus caterpillars have begun to hatch in the natural environment tank approximately 14 days after they were laid. In comparison, the sibling caterpillars subject to higher temperatures and consistent humidity levels inside hatched out after only 9-10 days.

Meanwhile, the Polyphemus caterpillars inside are completing their first molt, and are now entering into their second instar. Molting begins with caterpillars attaching their hind legs to a leaf with a thin strand of silk. Their facial plate is tight and shrunken, which means the caterpillars cannot feed at this time. Once the facial plate had dislocated, it reveals a new pale green facial plate beneath. The caterpillar then crawls out of its skin, which they eat afterwards. Molting is complete once the new facial plate turns brown and hardens, and the second instar caterpillars display bright orange-yellow spikes from head to tail.

The Cecropia caterpillars inside have begun to emerge. These small black larvae are about 5 mm in length. No sign of Cecropia caterpillars in the control tank yet.

The Cecropia caterpillars in the outside tank have begun to emerge 3-4 days after ones inside.

Only 2 of the indoor Cecropia caterpillars have survived. I speculate that their black coat may have caused them to overheat. Also, due to the age difference between the Cecropia and Polyphemus, the Polyphemus may be outcompeting the younger and smaller Cecropia. I have moved the 2 survivors to a new tank, and added 9 more Cecropia caterpillars from the outside tank to the inside tank.

The 2 surviving caterpillars are showing signs of molting, and appear yellow under the black skin. Soon they will enter their second instar. The Polyphemus caterpillars inside have also begun to molt into their third instar.

Second instar of Cecropia caterpillars

Fourth instar of Polyphemus caterpillar

The reason why the Cecropia larvae are dying may be due to a genetic problem. The Cecropia larvae outside have also begun to face massive die-offs, despite having no contact with the other species and are experiencing natural temperatures. The food source is also fine, since they and the other species are eating the leaves without trouble, so I can only assume that the dying species has unfavourable genetics, causing them to die quickly. I will still continue to observe the survivors.

The Cecropia caterpillars from the outside tanks barely seem to be growing at all. However there is a noticeable difference between them and the Cecropia caterpillars I took from the outside tank to the inside tank in order to replenish the stock. Despite being born and raised briefly in the same conditions, the Cecropia that I moved inside are now growing larger, and are quickly catching up with the weight and length of the two surviving larvae from the original temperature treated batch. The same trend appears with the Polyphemus larvae, however the size difference between the control and treated caterpillars is astonishing.

One of the Polyphemus caterpillars inside has spun a cocoon only 30 days after it hatched. I weighed the inside Polyphemus larvae again today, just to see what weight they were sitting at before they begin to cocoon, and they weigh in at a massive 7.3 grams. These caterpillars started at a weight of 7.8mg, which means they’ve increased in weight about 1000 times.

Unlike the Polyphemus caterpillars where siblings all look essentially the same, the Cecropia caterpillars will display variation in physical characteristics such as colour and eyespots.

Outside Polyphemus are entering into their fifth instar. All of the inside caterpillars have cocooned. The caterpillars outside should begin to cocoon within a week.

Due to the slow growth of the Cecropia's, I have caterpillars in four different instars at the same time. The small black caterpillar is a 2nd instar, the green-yellow caterpillar is a 3rd instar and the very colourful one is 4th instar.