Once you locate butterfly eggs, it is easy to gently roll them off the leaf with a finger and place them in the cup. Placing eggs in a hatching cup is one method to start them off in a closed safe environment. (Click on any photo to see a larger image.)
One of the safest methods to hatch eggs is with a 5.5 oz cup and lid. Other sizes work well. This is simply the size we prefer.
A punch or other item is used to make small holes in the lid. At the farm, we use a tool punch. At home, we use an ice pick. Any sharp item can be used. We punch one hole in each indent around the cup, for a total of 5 or 6 holes, depending upon the lid. Holes can be punched in the middle of the lid or wherever one prefers, as long as the holes are in the lid and not the cup itself. CAUTION: punches go through flesh easier than the lid. Use caution. Do not hold your finger under the area you are punching.
A coffee filter or piece of paper towel is trimmed an inch or so larger than the lid. These allow limited ventilation yet does not allow the eggs to dehydrate.
With this method, we do NOT add water or damp paper towels. Too much humidity invites growth of bacteria, mold, and disease. This method will keep eggs from dehydrating. (In containers with more ventilation, there may be a need for a drop of humidity.) We again emphasize the fact that too much humidity can cause disease and death.
1) Hatchling caterpillars are so small that they can crawl through holes punched in the lid. 2) A piece of paper towel can absorb a certain degree of humidity if leaves were added to the cup. For these two reasons, we use a dry paper towel between the cup and the lid.
Once you know the eggs are close to hatching, we add a small piece of fresh host plant leaf. Gulf Fritillary caterpillars eat passionvine. With most species, when eggs begin to turn dark, they will soon hatch. It may take an hour to two days after turning dark, depending upon the species.
Most butterfly eggs hatch within 3-6 days, depending on the temperature in the room where the eggs are located.
Use caution: do not place the cup where direct sunlight or heat will touch it. Direct sun causes the cup to become an oven. Keep the cup away from windows.
A caterpillar’s strongest instinct, for some species, is to go toward light. They will crawl away from food to the brightest side of the cup. When you add leaves, always add them on the bright side, touching the side of the cup.
If a caterpillar is on the side of the cup or on the leaf, not moving, do not move the caterpillar. It may be molting (crawling out of its old tight skin/cuticle). Although some species do fine if they are moved while molting, other species will die if they are moved during that time.
Some eggs may not hatch. If they are infertile, infected with trichogramma wasps, or damaged, caterpillars will not hatch.
Some species may eat unhatched eggs. It is best to scatter the eggs on the bottom of the cup instead of placing them all in one area of the bottom of the cup.
(The next page will soon be finished, taking the young caterpillars from the cup and raising them in a larger habitat. Obviously they can’t stay in this small cup for long!)