Friday, March 15, 2013

Adaptable Immigrants

Parry's Penstemon on the left, pink flowers
After an unusually cold January when temperatures dipped to -8C for several nights, in mid-February our Parry's Penstemon was already pushing up its new flower spikes. They seemed to grow fast enough to watch them get taller.

5th instar caterpillar, leaf-cradle pulled apart
 But two of the stems were bent and crippled.  Each one hosted a single leaf-rolling caterpillar in its tip. The caterpillar had pulled the young leaves into a cluster and thus interrupted the growth spurt, causing bending and twisting of the stem. As the caterpillars seemed close to their presumed final size, I collected the two culprits with enough plant material to finish their development. The rest of the penstemons survived a rare snow fall, and  now they are blooming beautifully.


On February 28th one of the caterpillars had pupated in a loose mesh of silk on the rim of the container and I thought the other one might have been killed by the fungus that eventually enveloped the collected plant tissue. I was wrong, I found another adult moth on the ceiling of my studio today.

Antigastra catalaunalis
 On the evening of March 13, a fresh new crambid moth fluttered out of the container. Avoiding the only light in the room, it spiraled right up to the ceiling, causing me to run to the garage for a step ladder and to take this overhead shot. While it's not the straight on dorsal photo that I was aiming for, it shows the flange on the front tibia that seems characteristic for the species. An elegant little moth and a mystery for a while - I had it on BugGuide and sent it to some friends who work with moths, but got no results. Until I posted it directly to Maury Heiman's fb page. Thanks again, Maury!

His Id lead to more information: The little moth in the family Crambidae (Crambid Snout Moths) » Subfamily Pyraustinae » Tribe Spilomelini » Genus Antigastra is called Antigastra catalaunalis (Sesame Leafroller Moth - Hodges#5181). It is an introduced species that is now widespread in tropical and subtropical regions of the world. In the US it is found from Southern Arizona to the eastern Mojave Desert and north to the northern areas of Utah.

Indian Insect Life: a Manual of the Insects of the Plains by Harold Maxwell-Lefroy.
Older descriptions which I found on Wikipedia call it an Indian Moth, but mention its migratory habits and a rather wide variety of host plants: The larvae feed on Antirrhinum, Linaria vulgaris, Sesame and Scrophulariaceae and Pedaliaceae species.

A research paper from India studying the moth's life cycle on Sesame as the host plant finds that warm temperatures and low rainfall and humidity favor population explosions of the moth. Those are conditions  that it will find here in Arizona.
In October of 2012, Carl Olson (duh, I could have just asked my friend and collegue right away!) found that reports were flooding in about unusual damage to landscape plants, such as Tecoma stans (yellow bells) and Tecoma alata (orange jubilee). Dark larval droppings, webbing and a loss of green leaf tissue were the obvious signs and symptoms of activity by the leaf-tier caterpillar, Antigastra catalaunalis. He suggested that since the caterpillars were tightly rolled up in leaves they were protected from most predators and contact pesticides but might be controlled using high doses of products based on Bacillus thuringiensis.

Since to our knowledge the moth hasn't been in Arizona for long, not much is known about its life cycle here, but I can now say that there is at least an early spring (Penstemon) and a summer (Tecoma) generation. These plants in the families Scrophulariaceae and Bigoniaceae and common in the wild as well as in landscaping around Pima ad Maricopa County. The landscaping plants, being grown in high concentrations and often under sub-optimal conditions, will probably suffer more than their wild relatives. I imagine that the population of the species might shoot up to an initial peak as many introduced species do, but then decline gain as diseases and predator populations catch up.  
In 2012 Carl Olson speculated that these immigrants may not be able to survive our occasional cold winters (the winter of 2011/12 had been very mild). But  my early collection date, right after the very heavy freeze of 2013 (Jan 13 to 16), indicates that the moth (its eggs?) might be rather freeze tolerant.


Penstemon parryi and Pipevine Swallowtail (Watercolor by M.Brummermann)









5 comments:

  1. Fascinating story as usual! When I saw your painting in my peripheral vision I thought it was a photo! So vibrant!

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  2. I love your painting, it's beautiful!

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  3. Gorgeous painting. I love the background particularly. Don't take that the wrong way! It's so clever the way it's blurry.

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  4. I also love your painting. The colors are fabulous and it would look great hanging on one of my walls!

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