Many phasmid species (luckily) accept quite a wide range of food plants we have available in Europe, they are polyphagous. So it is quite easy to find alternative food plant for them. Yet on the other hand, there are species which are specialized feeders. They accept only a very limited range of food plants, they are to some degree "monophagous". And this makes it difficult if not even impossible for most of us to breed such choosy species. And to make things worse, often such species with specific food requirements are often are very interesting phasmids, sometimes very colorful
The Coating Method offers a solution, which allows us to such choosy species too. The underlying hypothesis behind this method is, that phasmids are mainly guided by their taste to decide which plant is the "right" food plant. And that implies that spezialized species have a taste for certain specific plants. And this discourages them from feeding on other plants which do not have the proper taste. Still other food plants, even though they do not "taste" right, could very well be good-enough food plants. If these specialized species would only accept these plants....
The Coating Method in a nutshell....a surrogate food plant is coated with a paste made from fine powder of a well accepted food plant by such a specialized species. This coated food plant is left to dry-up thoroughly before introduced to the cage with the nymphs. Then put the coated food plant in the cage with the nymphs, and hopefully they are allured to start feeding. After some time, they then get used to the taste of the surrogate food plant, and then they will also eat this plant without a coating.
A similar method is actually applied in human nutrition on a very regular basis, called food flavouring. To keep us hooked on junk food :)
Below you see a freshly hatched nymph of Marmessoidea quadriguttata "Kubah" feeding on Salal which is coated with laurel (Laurus nobilis)
What is needed for the Coating Method
1) Leaf powder
- use fresh leaves of a well-accepted food plant. Make sure that you use "mature" leaves, not the very young leaves in spring
- carefully desiccate these leaves (at temperatures ≤ 50°C), like in an oven. Make sure the temperature does not rise too high!
- grind the dried leaves into a very fine powder (e.g. with an electric household spice mill / grinder). The finer the powder is, the better. Target for dust-fine powder !
- use a very fine sieve to get the dust-fine powder separated from the fibrous parts
- leaf powder can be stored in the freezer for years on end. So make a good amount, then you will have enough for a long, long time
2) How to prepare the coating paste
- mix some leaf powder well with water in a small container. This forms the coating mixture
- to about 20 ml of coating mixture, add about 10 drops of a preservative called "Sümo". This will help to keep mould growth in queck to some degree, while still being able to provide a rather high humidity for the young phasmid nymphs. Nevertheless, after about 7 - 10 days, mould will grow and the coated food plants have to be exchanged !
- this preservative "Sümo" is being used in large scale juice manufacturing. We got it from a german supplier, so look for "Sümo Konservierungsstoff". Sümo contains potassium sorbate (E-202) and sodium benzoate (E-211), maybe you find something similar in your country too...
- add very little of Xanthan (a common and natural thickener, also used in human nutrition), and mix for several minutes. This will increase the viscosity of the coating mixture (plant powder + water). A rather viscous coating mixture is needed, so that it will not just drop of the leave before it has dried. Be care so that you do not use too much Xanthan, otherwise the coating mixture will become too thick....
- one can even mix different leaf powders into the same paste if need be. For example oak (Quercus spp.) and Eucalyptus leaf powder, for species like Eurycnema (which feed well on oak and Eucalyptus).
- leftover, ready-to-use coating paste can be kept in the freezer, to be used for another coating later on
3) Surrogate food plants
- we prefer surrogate food plants which are hardy and stay fresh for as long as possible
- a good choice is Salal (Gaultheria shallon), as it usually keeps fresh enough for 2 weeks, sometimes even longer
- if Salal is not well accepted, then one can also try out other potential surrogate food plants, like bramble (Rubus spp.)
How this method works
- cut away the leaf margins of the surrogate food plant
- with a fine brush, apply a layer of the coating mixture on both sides of the surrogate food plant leaves
- allow the coating to dry up thoroughly for some hours
- put the coated food plant in the cage with the nymphs
- the pic above shows an Eurycnema versirubra nymph feeding on bramble which is coated with a mix of oak and Euclyptus
- keep a wet substrate on the cage floor in the cage with coated plants
- one can offer apple slice in the beginning too. This can also help to to get the nymphs started on feeding on the coated leaves. Remove the slices every day. And stop offering apple slices when they start to feed on the coated leaves
- usually after 7 - 10 days or so, the coating will get mouldy anyway. Then one has to put a freshly coated surrogate food plants in the cage, and discard the old one
- after nymphs have been fed for about 3 - 4 weeks on coated leaves, then one can try to offer food plants without coating. But do not forget to cut away the edges of the leaves!
- if they accept the food plant, then all is OK. If they don't, offer them a food plant with coating applied to just one side
- after another 3 - 4 weeks, again try to offer food plants without coating. By this time, the nymphs hopefully have adapted to the taste of the surrogate food plant - so that they will continue feeding without problems
Limitations of this method
- there are specialized feeders with which this method does not work, maybe because the surrogate food plant does not have the proper ingredients to keep the nymphs healthy
- an example for this is Oreophoetes topoense - a natural fern feeder. Nymph of this species are feeding well on bramble with a fern-coating. But such nymphs will not be as big as nymphs which feed on fern, and they die before they reach maturity
- also it was not possible to get nymphs of Eurynecroscia nigrofasciata "Tapah" nymphs to feed on a Litsea robusta coating, even though this species seems to feed on this plant in the wild
To be noted
- do never spray coated leaves with water
- some coatings do not get mouldy as quickly as others. Examples are coating prepared from Eucalyptus, oak (Quercus spp.), cherry laurel (Prunus laurocerasus), bay laurel (Laurus nobilis). These plants have inherent fungistatic qualities
Freshly hatched nymphs of Marmessoidea sp. "Bach Ma", feeding on Salal with a laurel (Laurus nobilis) coating
An adult male of Micadina sp. "Cuc Phuong", feeding on bramble with an oak coating