Finding Eggs in the Field > Eggs on New Growth or on Healthy Host Plants
Other females will seek out host plants that, for one reason or another, are healthier than other individual host plants. The reasons why these plants are healthier include the following:
- Plants are taking refuge under a shade source
- Plants are growing between rocks where the roots are healthier
- Plants have been naturally pruned by livestock creating healthier stalks when they grow back
- Plants are growing adjacent to a natural water source
- Plants respond to a wet winter
Female hackberry butterflies prefer to lay eggs on hackberry trees with new growth.
Many pierid butterflies use pinnate tansymustard (Descurainia pinnata) which grows best if taking refuge under or near a conifer, juniper, or larger tree, which protects it from direct sunlight.
Female Desert Swallowtails (Papilio coloro) prefer to oviposit on new growth of host turpentine broom (Thamnosma montana).
Female indra swallowtails prefer to lay eggs on plants that have the best chance of providing healthy stalks long enough for their caterpillars to make it to pupa. For many desert and/or otherwise xeric populations of Papilio indra, the plants with the healthiest roots are those growing between rocks where moisture is retained in those roots. Oftentimes, the stalks of Lomatium and Cymopterus plants growing out in the open burn up much faster than those growing between rocks.
Some Cymopterus terebinthinus petraeus plants can be quite healthy (forgive me if this photo doesn't exactly project this idea) if they are growing at the base of a wash adjacent to a butte in Utah and Colorado badlands. These plants become targets for female P. indra minori to oviposit.