Incubation

Detailed information on different incubation techniques:

Cup-Incubation method - basic method for separated incubation.

Glued-Eggs Technique (GET) - specifically for egg-glueing species.

Stuck-Eggs Technique (SET) - specifically for leaf-piercing species.

 

General remarks about incubation

  • Sort out eggs regularly from the cages and incubate them separately, as it is best to kept and raise nymphs separately from adults.
  • This way it is much easier to keep an overview on the various stages of development, control the number of hatching nymphs and prevent uncontrolled, destructive overpopulation in the cages.
  • The size of the incubation boxes should be appropriate to the size of the hatching nymphs.
  • If the incubation boxes are too small, then the hatching nymphs will disturb each other. This will result in crippled, often non-viable nymphs (badly bent or missing legs, crippled bodies).
  • Short dry periods (few days in row or a one-time delivery by mail) does not harm the eggs of most species.
  • However, if the dry period lasts too long (several weeks) then the embryos in the eggs may die.
  • If eggs are kept dry during hatching, then the hatchling might get stuck in the egg and won't be viable.
  • On the other hand, don't incubate eggs on a very moist substrate. This does also damage the eggs, they might die and it encourages mould growth.
  • Vermiculite with a medium moisture is a very good substratum for incubation.

Hatching

  • Nymphs of different species (genera) hatch during different times of the day.
  • Nymphs of most species hatch under the veil of darkness, during the night.
  • But there are also species (genera) which always hatch during daylight hours, usually in the early morning or around noon - for example Achrioptera, Cranidium, Phyllium, Trychopeplus, Pterinoxylus.
  • The embryo, which is about to hatch, must be able to somehow perceive when is the correct section of the day. Perhaps they can "estimate" the right time by the raising temperatures in the morning? Another possibility is that they perceive the change in light (night-day). But because of the often thick and dark egg shell the 2nd option seems less likely.
  • Having this in mind, it seems advantageous that the eggs are subjected to a "natural" nocturnal temperature drop and a day-night light cycle.
  • Immediately after hatching, a hatchling pumps up it's body with air which then lenghtens / expands quite a bit.It is important that hatching nymphs are not disturbed during this crucial phase.
  • If the hatching nymphs feel disturbed during this early phase just after hatching, then they tend to "forget" and skip expanding their bodies. The exoskeleton then hardens without going through the proper expansion process. And this leads squatty, dwarfish nymphs, thus we call this the "Dwarf Syndrome".
  • Such dwarf nymphs often die prematurely. It seems that without the proper bodily expansion right after hatching, their intestines and other inner organs remain compressed and thus do not work properly.
  • This dwarf syndrom is more frequent observed in species with long-legged, large nymphs, like for example Pharnacia, Phasmotaenia, Tirachoidea, Trychopeplus. Yet this problem is rarely observed for species with stout nymphs, like for Phyllium,Trachyaretaon, Dares, Mearnsiana, Haaniella.
  • Disturbances to be avoided during this critical phase shortly after hatching:
    • Moving the incubation box
    • Too many nymphs hatching at the same time in a narrow, small incubation box
    • Loud music or noise
    • Commotion around the hatching boxes
    • Of course, hatchlings should remain only a short time in the incubation box

Mould

  • Eggs of some species or genera (e.g. Phasmotaenia, Eucarcharus, Hermarchus, Phasma, Xenophasmina, Phyllium) tend to get mouldy rather quickly and often it is difficult to completely avoid it. Thus eggs of such species should not be kept too humid.
  • The negative effects of mould on phasmid eggs is however somewhat overrated.
  • As long as there is no excessive mould growth, the hatching ratio will not be badly affected.
  • Nevertheless this does not mean that we are careless when it comes to mould. In the end it is also beneficial for our own health to reduce mould growth to a minimum.
  • If eggs are covered with a layer of mould, then we can clean them carefully in a tea strainer under lukewarm water with a soft brush.
  • If vermiculite is being used as incubation substrate, then the eggs can be covered with a thin layer of vermiculite (2 - 3 mm high). This helps to reduce mould growth. Additionally this layer of vermiculite helps nymphs to free themselves from the egg shell more easily.
  • Springtails (Collembola) can be used in the incubation boxes to reduce mould growth.
  • Some breeders use isopods (Isopoda) to minimize mould growth. But it is not known to us whether isopods can "crack open" and destroy phasmid eggs.

Incubation substrate vermiculite

  • Vermiculite is very suitable for egg incubation.
  • Vermiculite itself can't get mouldy, as it is an inorganic, biologically inert mineral. Therefore vermiculite it is better suited as an incubation substratum than peat, coir, paper or cotton.
  • Vermiculite absorbs water very well and gives off the water as (air) humidity. Thus the eggs won't be in direct contact with moistness. And therefore vermiculite is also the better suited incubation substratum than sand.
  • We use fine-grained vermiculite (about 1 - 2 mm), but coarser-grained vermiculite (grain size 3- 5 mm) should be equally well suitable.
  • Vermiculite of poor quality contains a lot of powdery material, which can hardly absorb any water. Thus the powdery material should be sift from the vermiculite before using it.
  • Vermiculite for incubation is kept at a medium moisture.
  • Too much moisture should be avoided, incubating eggs too moistly is a common mistake amongst phasmid breeders.
  • How to find the right medium moisture for your vermiculite ?
    • Vermiculite from different sources (or different brands) may vary in it's ability to absorb water. Therefore an absorption test is needed before you are first using your vermiculite (and whenever you have vermiculite from a new source).
    • There is always some powdery material in the vermiculite, which does not absorb water effectively. This powdery portion must be sieved out with a very fine sieve.
    • To determine the maximum amount of water your vermiculite is able to absorb, weigh dry vermiculite (for example 10 g, use a small digital letter scale) in a small narrow cup. Then slowly add water (again use the digital letter scale) to the point where no additional water is being absorbed and the vermiculite surface starts to glisten moistly / watery. And this gives you the maximum H2O absorption ratio for your vermiculite.
    • About 45- 50% of that maximum H2O absorption ratio is needed to get an medium moisture, which is good-enough for incubating eggs of species from tropical, humid areas. This should result in a humidity of about 85+% RH within the cup-incubation unit.
    • A sample calculation: if you weigh 10 g of vermiculite and then you have to add about 40 g of water until the vermiculite surface starts glistening watery, then the maximum H2O absorption ratio for that vermiculite is about 1 : 4 (vermiculite : water). Then use about 50% to get a medium moisture, which is 1 : 2 (vermiculite : water) or 10 g vermiculite (in the incubation container and 20 g water.
    • Rule of thumb. Vermiculite with a good enough medium moisture feels almost dry to the touch (after one day) and it does not glisten moistly.
  • Incubation moisture on vermiculite for species with different requirements:
    1. Species from tropical, humid areas.
      • Use about 45 - 50% of the maximum H2O absorption ratio.
    2. For species from dry or moderately dry areas.
      • E.g. for species like Agathemera, Bactrododema.
      • Use just slightly moist vermiculite.
      • Use about 15% of the maximum H2O absorption ratio.
      • Increase the ventilation areas on the incubation container.
    3. For species which glue or stick their eggs onto /into leaves, twigs, bark ect.
      • A natural incubation condition means that such eggs are not in direct and constant contact with a humid substratum.
      • In our experience, eggs of such species often get mouldy quickly when kept too moist or when they are in direct contact with a humid substratum.
      • Use GET or SET method, which are near-natural incubation setups.
      • Use about 60% of the maximum H2O absorption ratio, but make sure that the eggs are not in direct contact with the incubation substratum.