Poladryas arachne arachne

Photo Life HistoryPoladryas arachne arachne

Habitat:  Pinyon Juniper; Desert Hills & Mountains; i.e, Utah's West Desert Mountain Ranges

Host Plants:  Penstemon confusus; Penstemon utahensis

Suitable Lab Host PlantsPenstemon eatonii; Penstemon cyananthus.  (It is a lot easier to get first instar larvae to initiate feeding on many species of Penstemon than it is to get late instar larvae to switch to those same species of Penstemon.)

Caring for Live Female Butterflies:  Feed females regularly.

Methods of Female Oviposition:  Open Screen Cages; Portable Cages.

How to Find Eggs:  With this butterfly, it is helpful to know that the butterfly actually flies in a certain location before exploring hostplants for eggs.  Like many other desert checkerspots, populations of P. arachne arachne can fluctuate, expand, and retract based upon weather, parasitism, and other environmental factors.  To find eggs, look on the ventral side of leaves towards the lower portion of the host plant.  In Utah's West Desert Mountain Ranges, females lay clutches of only  4-8 eggs per plant on Penstemon confusus.  In Southern Utah, females lay eggs in larger clutches on Penstemon utahensis

How to Hatch Eggs:  Consolidate eggs into one container.

How to Find Caterpillars in the Field:  Post-diapause larvae can be found either resting at the base of the host, a few feet away from the host, or feeding on host plant flowers or leaves.  Keep in mind that once you find one post-diapause larva, start looking closer in that general area as post-diapause larvae disperse from where sibling pre-diapause larvae fed.  It is sometimes possible to find a several post-diapause larvae on a single plant if the species of Penstemon is large enough to support multiple post-diapause larvae.

Caterpillar setups:  For pre-diapause larvae, I recommend using the open terrariums or open bucket technique.  Overcrowding is not generally an issue.  For post-diapause larvae, use the twin cup method, potted plant method, or open terrarium method,  With the open terrarium method, place paper towels semi-scrunched adjacent to bottled plant to make sure that exiting larvae can easily crawl back to host.

Larva to Pupa:  Caterpillar silks to leaf or twig; creates and attaches cremaster; hanging as a J before pupating.

Number of Broods per Year: 1-2; depending upon location.

Overwintering Stage:  Third Instar Larva.  

Overwintering Strategies: Your Own Backyard.

Post-Hibernation Strategies: When you feed post-diapause larvae after overwintering, if you're only rearing a few caterpillars, I highly recommend isolating caterpillars from sibling caterpillars using the twin cup method (or similar) in order to avoid re-diapause--an extremely common situation with checkerspots that fly in the desert.  (See this video for more information on the twin cup method.)

Avoiding Diapause Techniques:  A certain percentage of larvae from univoltine populations from Utah's West Desert can avoid diapause and feed straight through to pupa if you provide them with fleshy or healthy host plant and expose larvae to 24 hours of light.  Larvae from southern Utah and Arizona also can feed through to pupation if provided with healthy host plant and 24 hours of light.

Disease Prevention:  Change out host plant and remove frass every two to three days using the twin cup method; every 4-5 days using the open terrarium method. 

Emergence:  Emergence Container

Field Notes:  Populations in Utah's West Desert can go through drastic fluctuations when host Penstemon confusus expands and retracts depending upon rainfall.