Breeding report Actias dubernardi (Oberthür, 1897)
Manuel Andreas Staggl1,2,3
1 Ludwig-Maximilians-Universität München, Department of Biology II, Planegg-Martinsried, Germany
2SNSB- Bavarian State Collection of Zoology, Münchhausenstraße 21, 81247 München, Germany
3Fakultät für Lebenswissenschaften, Universität Wien, Althanstr. 14, 1090 Wien, Austria
In the following I would like to give a short summary of my breeding of Actias dubernardi. Basically, I had two parallel breedings. One part I got as caterpillars in the second larval stage, the other as eggs. For this reason, I will refer to the latter approach when reporting on egg development up to L2, and mainly to the former from L2 onwards.
Actias dubernardi, as a highland species, seem to prefer humid and cooler conditions with higher temperatures during the day and a clear drop in temperature during the night. It seems to be advantageous to simulate these conditions in breeding. The breeding containers were stored on an unheated window sill. On the side facing the window there was some condensation, which was not problematic.
Possible food plants:
As food plants, mainly representatives of the conifers (Coniferales) come into consideration. The natural food plant seems to be pine (Pinus sp.). However, there are reports of successful breeding with European Larch (Larix decidua), Nordmann Fir (Abies nordmaniana) and European Spruce (Picea abies). Since in my case only Pinus nigra, Pinus mugo and Douglasia sp. were available, I chose these as food plants. Since all conifers can be highly resinous, it is important to coat the twigs at the cut ends, otherwise the caterpillars will stick to the resin. I chose the variant ehere the the fresh cutting is dipped twice in liquid candle wax to seal it. The branches were replaced every few days. The animals were transferred to the new branch on the needle of the old branch. The needle was put loosely in between of the fresh food plants.
2. Breeding record:
The eggs were stored in small 5ml cream jars. Before closing the jars, the eggs were breathed into them a few times to ensure a certain basic humidity. This was repeated every 2-3 days. Storage at room temperature, approx. 22°C. Hatching occurred after 13-14 days.
An approximatly 1.5l Tupperware box was chosen as the container. A double layer of kitchen paper was placed on the bottom, which was moistened with a few pumps of a spray bottle. A small digital thermometer/hygrometer was placed in each box to monitor temperature and humidity. The temperature was between 21 and 22 degrees during the day and between 18 and 20 degrees at night. The humidity was very constant at 99%.
After hatching, the caterpillars (approx.5mm) were removed from the box with a fine hair brush by a slight twist of the brush and transferred to a small branch of food plant, always about ten caterpillars per box. A light mist from the spray bottle was gratefully accepted and the caterpillars drank the fine droplets from the surface of the food plants. Pinus mugo and Douglasia sp. were offered as food plants. P.mugo was accepted immediately, Douglasia a little more hesitantly.
There were a few losses on the first night, which seems to be typical for L1. The caterpillars are generally considered very vulnerable in this larval stage. The problematic point seemed to me to be the humidity. The caterpillars seem to need really humid conditions. Better a little too moist than too dry. Subsequently they were kept more humid and there were no more significant losses. Every day the kitchen paper was replaced and the box was wiped out and dried. Every third day the box was changed and the used one was cleaned thoroughly.
After six days, the first ones were in moulting dormancy to L2 at a size of approx. 8mm. First L2 then after seven days.
The L2 had a size of about 11mm. The animals on the Douglasia seem to be much smaller and take longer to develop (Fig 1). The rearing conditions were the same as in L1. After eleven days, the first animals were in moulting dormancy to L3 (size approx. 10-14mm).
Figure 1: Actias dubernardi Instar 2 on Douglasia sp.
After 13 days all were in L3 (12-25mm) (Fig.2) and were transferred ten at a time into a 5l Sammla box (IKEA) with moist kitchen paper on the ground. From this larval stage onwards, Pinus nigra was offered in addition to Pinus mugo. However, as their needles were very coarse, they were accepted only hesitantly. After 17 days, the first ones were in moulting dormancy to L4 (15-20mm) (see Fig. 3).
Figure 2:Actias dubernardi Instar 3 auf Douglasia sp.
Figure 3: Actias dubernardi instar 3 in moulting dormancy to the fourth instar on Pinus mugo.
fter 19 days the first were in L4 (ca.20mm) (Fig. 4). After 24 days, all were in L4 (25-35mm). Especially those on Douglasia are clearly slower in development and still smaller. For this reason, Pinus mugo was gradually offered in addition and preferred by the animals in each case, and therefore the Douglasia was increasingly reduced in the food offer. The temperature was between 18 and 20°C and the humidity was still 99%. From this stage onwards, the animals seemed to sit more directly on the branches and not on the needles as before.
After 27 days, the first were in moulting dormancy to L5 (30-35mm).
Figure 4: Actias dubernardi instar 4 on Pinus mugo.
After 30 days the first caterpillars were in L5 (length 30-40mm, weight 1g, Fig. 6). The animals were transferred to 11l Sammla and only P.mugo and P.nigra were offered. P.mugo was clearly preferred, and thus gradually completely switched to this pine. Figure 5 shows a caterpillar in L5 compared to L4. After 33 days, all were in L5. After 32 days 2g, 33 days 3g, 34 days 4g (35-45mm). After 36 days 5g, after 38 days 6g (40-55mm). After 3 days first two 7g and 65mm. After 41 days 8g.
On the 42nd day the first 3 excreted out and turned dark jade green (see fig. 7). They were placed in a 5 litre Sammla with a branch of Pinus nigra and dried moss. The moss seems to be preferred and the animals crawl into or under it and start to spin a cocoon.
fter 44 days most of them were pupating. The larvae were divided into a 5L and an 11L box for pupation. The 11L box was only filled with pine branches. They crawled between the needles and spun their cocoon there. A few also started to spin on the bottom of the box under the branches. The lower part of these remained open (see Fig. 8, cocoon in the lower row, second from the right).
Figure 5: Actias dubernardi Instar 4 compared to Instar 5 on Pinus mugo.
Figure 6: Actias dubernardi instar 5 on Pinus mugo.
Figure 7: Actias dubernardi Instar 5 left and middle already darkened, ready to pupate, right still feeding.
Figure 9: Actias dubernardi cocoons, lower row, second from right with unclosed cocoon
The first two moths (males) eclosed after 35 days from the pupation date. The following day, two more males hatched (35 days after pupation). The first female hatched after 37 days, the second one the following day also after 37 days.
Mating already succeeded on the first night with a sex ratio of 1:2/W:M in a standard 60x40x40cm pop-up flight cage. This was placed freely on the floor in a completely darkened room. Occasionally it was checked by a red light lamp, which did not seem to bother the animals. To create a gentle air circulation, the radiator was turned up a little. The first eggs were laid on the second night. Mostly in smaller piles randomly on the floor and the walls of the flight cage.
Figure 9: Actias dubernardi, Imago, Female
Figure 11: Actias dubernardi, Imago, Male
3. Discussion on the food plants:
The three chosen food plants seem to be suitable for breeding Actias dubernardi with some restrictions.
Douglasia sp: was accepted after a short hesitation and then eaten well. The needles are soft and relatively juicy, which seems to provide good moisture for the caterpillars. Nevertheless, this food source probably does not offer as much energy as the two Pinus species, as the caterpillars grew much slower and switched to the next skin later. After switching to Pinus mugo, however, the caterpillars caught up well and when they pupated there were no longer any significant differences to the individuals that had been raised on Pinus from the beginning.
Pinus nigra: Was fed to the older larval stages. The needles are very long and thick. And therefore show a good "leaf mass". However, the needles are very coarse and therefore not as popular as P.mugo.
Pinus mugo: Soft, juicy to almost fleshy needles of medium length. The branches remained fresh for several days. This food plant was well accepted from the beginning and the caterpillars grew to a very good size. Highly recommended!