Eggs and Pupae Care in Butterflies and Moths
Lepidoptera eggs show a great variability in shape and color. The egg contains the embryo that hatches fully functional. The larval period is called post-embryonic development. Eggs are usually rounded, from 0,1cm to 0,3cm in diameter.
The duration of embryo development is strongly affected by temperature, every species has its own timing. Most caterpillars in about 2 weeks after egg laying. This means that eggs need to be shipped as soon as possible after being laid, to be safely received. We always ship eggs which are maximum 48h old. For some species, the egg is the stage that undergoes diapause (ex. A. yamamay).
Attacus lorquinii egg, picture taken with an optic stereomicroscope
Eggs are usually shipped into small plastic tubes. Once received, they need to be moved to a bigger container, allowing caterpillars to have enough space to hatch and move.
Standard 80mm plastic Petri dishes (fig.A) are a very common tools to store the eggs and let the caterpillars hatch inside. Check our Petri dishes. Other kind of small plastic boxes can be used; it is recommended to perform holes or modify the boxes to allow aeration. Close the boxes with a fine mesh, tulle is widely used for this purpose (fig.B). Check our plastic boxes. Avoid the use of medium/big boxes because caterpillars will tend to move a lot and spread inside the box.
Do not put the leaves before the first caterpillars hatch. The presence of leaves inside a small environment can “poison” the air and reduce the hatching rate. This is especially true in case of toxic plants like Prunus laurocerasus.
To increase humidity (very useful with tropical species) place a small piece of wet paper inside the Petri dish or the box, alternatively it is possible to spray the lid of either the Petri dish or the plastic container. Avoid cotton because small caterpillars may remain trapped into its filaments, this is especially dangerous with Sphingidae or Brahmaeidae caterpillars. Another strategy is to keep the eggs on top of wet paper inside a modified cage as shown in fig.B.
Pupa is the stage in which metamorphosis takes place. Depending on the species, pupae can be nude or protected inside a cocoon. The cocoon is produced by the caterpillar and is not part of the insect’s body. Some species produce a very loose or incomplete cocoon.
Lepidoptera pupae can weight 1 gram or less, while some species, as Argema mittrei, reach up to 15-20g. They can be safely shipped in small or medium parcels. Once received, the care needed depends strictly on the species’ cycle coupled to the current season. For pupae that are expected to hatch at RoomTemperature is sufficient to place them in the bottom of rearing cages (Check ou rearing cages), better over some paper which retains humidity or just to keep the cage itself clean from meconium. Meconium is the earliest stool of an adult insect, it doesn’t stink and it’s easily cleaned with water. Many tropical species require increased humidity to properly hatch, spray the pupae often (with water) to this purpose. To stimulate pupae in hatching, they can be submerged in warm water for 1-5 minutes, then moved back to their place; this operation can be be performed once every two days or even more (very effective with Saturniidae). Tropical pupae, and all the pupae that are expected to hatch during the hot season, can be awaken with this method. This procedure helps in synchronizing adults emergence, which is a key factor to obtain pairings.
Example of Pupae from Saturniidae (Lepidoptera family), from left to right: Argema mittrei, Attacus atlas, Antheraea jana, Cricula trifenestrata
Samia ricini male, genitals are positioned in the 5° segment, start counting after the underwing segment. In a female specimen genitals are positioned across the 4° and the 5° segment; they present a different “V-like” shape. Another recognizable feature in Saturniidae is the antennae sexual dimorphism, males usually present thicker ones.