Palpita vitrealis - Olive-tree Pearl moth

Some notes on keeping Palpita vitrealis

This moth is an uncommon migrant to the UK. It is known by a variety of common names. Olive-tree Pearl, Jasmine moth or White Pearl. Abroad, the species is reported to feed on jasmine (Jasminium) and olive (Olea). 

Late summer/early autumn 2023 saw numerous migrant moths taking advantage of winds coming from the continent to the UK. This was the first year I have recorded Palpita vitrealis in my Berkshire garden, in fact it is the first time I have seen the moth. 

A small number of the moth came to my light trap over a period of days. I retained one with a fattish body in the hope that it might be a female, overnight and was rewarded with some tiny, almost transparent eggs the next day.

According to Wikipedia, these moths mainly fly from August till late October, depending on the location. They feed on nectar of various flowers, including ivy and buddleia.[6][7] This species shows a migratory nature. The larvae are initially yellow, later becoming green. They can grow to a length of about 2 cms. They feed on the leaves of the host plants, mainly jasmine (Jasminum officinale), privet (Ligustrum species), Forsythia, Arbutus unedo and European olive (Olea europaea). [7] In Africa the preferred host plants are Sida rhombifolia, Grewia, Helicteres isora, Schima noronhae and Randia scortechinii. [2] The larvae are considered a pest of olive fields, as they attack the leaves and fruits. The final instar of the larvae spins some leaves together and form a silky cocoon to pupate

16/11/2023

Today I am attending to the larvae of Palpita vitrealis.

These were previously divided into three groups, as experience has shown that if disaster strikes, this provides some mitigation against losing them all. They are being kept indoors at room temperature because I do not know how they overwinter abroad. Are they continuously brooded or are they able to hibernate?

GROUP 1. 

This group of larvae were kept, in the traditional method for young larvae, in a tub containing privet leaves. These were all fresh leaves. The pot was first washed and dried and then lined with a piece of kitchen paper. Then the larvae were added and then the leaves laid on top. 

Because of their habit of spinning silk on the leaves and pulling the leaves over themselves to make a shelter, from within which they feed, the leaves can get into a bad state, eventually going completely brown and limp and rotten, but the larvae are reluctant to leave their protective shelter. Obviously, when the leaves are on a living plant, they remain fresh and the larvae have no need to move on until they have eaten the whole leaf. 

To keep the leaves fresh, the pot was kept closed and airtight, but this had the down side of making the decaying leaves prone to mould if left too long. 

A balance has to be struck between not removing the larvae from sub-optimal quality leaves too often (where they will presumably use additional resources constructing an new shelter, and leaving the leaves too long with the risk of mould and disease.

GROUP 2. 

Larvae were kept on stems of privet in water in a wine bottle with the opening stuffed to prevent any larvae venturing in to the water. 

The sprigs of privet were not caged or contained in anyway, so there was plenty of fresh air, and thus no mould problem. 

GROUP 3. 

A margarine tub with privet leaves from the last cleaning out of the larvae. I kept all of the leaves in a tub, in case I had missed any larvae as they were very small. As it turns out I was able to find about 15 larvae that had been previously missed.

I am repeating this procedure (keeping the old leaves in a tub) as I attend to them this time. Although the larvae are a bit larger now, they do vary in size and it is still possible to miss the odd one. This time I am using a larger tub to allow air to circulate.

I have now ended up with 3 groups of larvae again. 

GROUP 1. 

Below, is a container with both privet and olive leaves in it. The cut ends of the olive stems are wrapped in kitchen paper, and placed in a plastic bag which is partially filled with water. This is then sealed with Sellotape to prevent larvae getting into the water. I am experimenting with olive leaves as well as privet, to see if the larvae are happy to change foodplants, and also to see if the olive leaves remain palatable  for as long as the privet leaves. A proportion of the larvae were placed into this setup.

GROUP 2. 

Fresh privet was placed into a wine bottle and the opening was sealed with crumpled aluminium foil. A selection of larvae were individually transferred to this set up. Again, as can be seen in the photo below, there is no containment. 

In the morning, I could not find any of the larvae, although I could see evidence of feeding on the leaves where I had placed them. This is a puzzle. had they climbed down the stems after feeding? Or had they descended on silken strands, perhaps to hibernate in the leaf litter that would inevitably be beneath the plant they were feeding on. They would have been out of luck here as there is just a wooded floor. Perhaps they have wandered off somewhere unsuitable.

GROUP 3.

A larger tub was used to save all of the old leaves that may still have larvae on them.

16/12/2023

The first of the adults have emerged - 5 as of this morning. The first one emerged on the Berkshire Moth Group meeting night Thursday 14th December.

As an update, changing the foodplant to olive rather than privet proved to be a good idea. The leaves did not seem to degrade as quickly.

Another thing that worked very well, was saving the old leaves in a plastic tub. All though I checked each leaf for tiny larvae, some evidently escaped me, and later I found near full-grown caterpillars on the side of the tub, which I transferred to another container with fresh olive leaves for their final feed before pupation.

Prior to the first frosts of the winter, I paced about 10 small larvae in a sleeve of black nylon mesh on the olive tree in the garden. This was done as an experiment to see if they were able to survive a British winter.

I also made contact with xxxx who is based on the Isle of Wight. Inspired by my experiment he has decided to do the same. It will be interesting to see what we learn.

The next stage of my plan, assuming successful pairings of this brood of moths, is to sleeve out more of them. Options I am considering include:

• Putting a female moth into a sleeve to let her lay on the olive naturally. 
• Putting some eggs loose into a sleeve
• Putting some young larvae into a sleeve.

We have only had two proper frosty nights so far, so putting this next generation into sleeves on the olive tree in the garden is not too far removed from putting them out for the whole winter.

20/12/2023

There are now 12 adult moths in a flight cage. I have not observed any signs of mating.

I asked AI Bard the following question:

What is the lowest temperature that the moth Palpita vitrealis can survive?

Unfortunately, there isn't readily available information on the specific lowest temperature the moth Palpita vitrealis can survive. This may be due to several factors:

• Limited research: This moth species isn't particularly well-studied, especially compared to common or economically important species. Consequently, research on its cold tolerance may be lacking.
• Variable tolerance: Tolerance to cold temperatures can vary significantly within and between moth species, depending on factors like life stage, acclimation, and specific genetic variations. This makes it difficult to pinpoint a single definitive value.
• Geographic range: Palpita vitrealis has a relatively wide geographic range, encompassing areas with diverse climates. Studying its cold tolerance across such a range would require extensive research efforts.

However, there are some clues that might offer some insights:

• Habitat and distribution: P. vitrealis primarily inhabits warmer regions like southern Europe and coastal areas of the UK. This suggests that it probably doesn't have exceptionally high cold tolerance compared to moths adapted to harsher northern environments.
• Flight season: It typically flies from June to December, implying it can survive moderate autumn and early winter temperatures, likely not dipping too far below freezing.
• General moth adaptations: Moths have various mechanisms for surviving cold, including supercooling (decreasing body temperature without freezing), metabolic adjustments, and utilizing shelters. P. vitrealis likely employs some of these strategies, but their specific effectiveness wouldn't translate to a precise temperature threshold.

In conclusion, while the exact lowest temperature Palpita vitrealis can survive remains unknown, the available information suggests a moderate cold tolerance likely above freezing temperatures during its active season. Further research, particularly involving controlled temperature experiments, is needed to determine a more accurate value.

If you're interested in learning more about this moth or cold tolerance in insects in general, I'd be happy to help you find additional resources. Just let me know how I can assist further.

I then asked:

How does the moth Palpita vitrealis spend the winter

Bard responded

Palpita vitrealis adopts a fascinating migratory strategy to spend the winter: it does not actually stay in its native habitat over the season. Instead, it migrates southwards to areas with warmer temperatures and readily available food sources.

Here's how it works:

Migration:

• As autumn approaches, adult P. vitrealis moths embark on a southward journey, primarily targeting the Mediterranean region and North Africa. This migration can span hundreds of kilometers.
• Flight activity usually peaks in September and October, with individuals often forming large, loose aggregations during their travels.

Overwintering:

• Once they reach their southern destinations, the moths enter a hibernation-like state, known as diapause. During this period, their reproductive activity and development slow down significantly.
• They likely find shelter in protected areas like crevices or vegetation to conserve energy and avoid harsh weather conditions.
• While their exact food sources during diapause aren't fully documented, they might utilize nectar from evergreen plants or other available sugary resources.

Returning home:

• As spring arrives and temperatures rise in their original habitat, P. vitrealis emerges from diapause and makes the journey back north.
• The returning individuals lay eggs on suitable host plants, allowing the next generation to thrive during the warmer months.

This remarkable migratory cycle allows P. vitrealis to escape the harsh winters and ensure the continuation of its population. It also emphasizes the complex adaptations and resilience of insects in navigating seasonal changes.

Additional points:

• While migration is the primary strategy, some individuals might attempt to survive the winter in milder parts of their native range, though their success rate is likely lower.
• Research suggests that climate change, with milder winters and prolonged growing seasons, may be influencing the migration patterns of P. vitrealis, potentially extending its northern range.

I hope this information provides a clearer picture of how Palpita vitrealis spends its winter months and the fascinating biological processes involved.

Q? 1 The information I shared about Palpita vitrealis's winter behavior comes from a combination of several sources, including: Scientific articles: I primarily relied on peer-reviewed research articles published in reputable scientific journals. These articles offer detailed information on the moth's migration patterns, diapause mechanisms, and ecological adaptations. Some key examples include: "Migrations of the moth Palpita vitrealis (Lepidoptera: Pyralidae) across the western Mediterranean Sea" by W.R.C. Roeleveld et al. (2002) "Life cycle and control of the glasshouse white-spotted yellow moth (Palpita vitrealis)" by H.J.C. Griffiths (1974) "The influence of climate change on the geographical distribution and abundance of insects" by A.D.B. Phillips et al. (2010) Entomological resources: I consulted websites and databases maintained by entomology societies and research institutions. These resources provide valuable information on moth species, including their taxonomy, habitat preferences, and behavior. Examples include: UK moths website: https://ukmoths.org.uk/ European Butterfly and Moth Recording Scheme: https://butterfly-conservation.org/butterflies/recording-and-monitoring CABI Bioscience - Invasive Species Compendium: https://www.cabi.org/Uploads/CABI/publishing/promotional-materials/insert/IS%20Compendium%20-%20A4%20Insert.pdf General scientific databases: I utilized comprehensive databases like Web of Science and Google Scholar to conduct a thorough search for relevant research articles and studies. By drawing on these diverse sources, I aimed to provide you with a well-rounded and accurate understanding of Palpita vitrealis's winter behavior. If you'd like to learn more about any specific aspect of the information I shared, I can point you towards the relevant article or resource for further reading. Please let me know if you have any other questions or if you'd like me to delve deeper into any particular aspect of this fascinating moth.

21/12/2023

Mating pair observed.

22/12/2023

Still have about a dozen adult moths. Today I will set-up an arrangement for egg laying.

Count of moths:

Dead = 3

Alive = 14

Olive sprigs in water - may encourage egg-laying

Sugar water. I have observed a couple of the moths feeding on this.

24/12/2023

There have been more pairings, but I have not seen any eggs yet.

The moths have been kept in the conservatory where the temperature is around 14 degrees C. They become active almost as soon as it gets dark. Flying and pairing observed at 5pm yesterday.