Click on the link to download and print pdf of the reference:

Sourakov, A. 2009. On polyphenism of Eurema daira in Florida.  News of Lepidopterists’ Society. 51(1): 38-40.

 

Here, I present a short photo essay, depicting two seasonal forms of Barred Yellow butterfly, Eurema daira.  Daniels (1995) suggested that the observed seasonal polyphenism “may enhance thermoregulation and/or crypsis for dry season form individuals faced with cooler conditions and distinctly different vegetative landscapes.” The photographs presented here that were taken in July (A, B) and December (C, D) at the same hour and on the same spot support crypsis theory.  The observed changes in coloration seem to also correspond to changes in behavior.  While in the summer, a disturbed E. daira tends to escape into the vegetation and hide under leaves, where it can be easily mistaken for one of the numerous white flowers, the winter form seeks refuge on the ground, blending with the fallen leaves. 

 Brakefield and Larsen (1984) argue, that dry season and wet season divergent phenotypes of Bicyclus are nothing else but anti-predator adaptations. The wet season form’s large eyespots, they suggest, function in the deflection of attacks, while the dry season individuals that have small or no spots are cryptic. They note that change in this species also corresponds to behavior: wet season butterflies are more active than dry season ones and, as they put it, “reproductive success is optimized in each season by interaction of phenotype and behavior.”  

 It has been suggested that “the phenotypic plasticity is to be expected to be built in every genome for every character since it is the primitive character that is governed by physiological processes sensitive to such environmental variables as temperature, nutrient supply, ionic environment...”  Frederick Nijhout’s laboratory at Duke University has been making a tremendous progress in understanding physiology of phenotypic plasticity in Lepidoptera (e.g., Rountree and Nijhout, 1995; Suzuki and Nijhout, 2008).  These studies suggest that a mutation that makes the phenotype sensitive to environmental and genetic changes at a single locus can uncover cryptic genetic variation for plasticity.  Nijhout’s model assumes presence of selective pressure (such as predators) on continuous polygenic reaction norm, which leads to evolution of distinct phenotypes, suggesting therefore that evolution of polyphenism is “consistent with the adaptive evolution theory.”  Though selectionist explanations have led evolutionary ecologists astray in the past (as it might have been the case with industrial melanism in peppered moths (Hooper, 2002)), such explanations are as highly probable, as their ecological testing is difficult. 

Seasonal forms of Eurema daira (Pieridae) in Florida exhibiting season-specific crypsis. ©Andrei Sourakov

 

References

 

Brakefield P. M. & T. B. Larsen 1984. The evolutionary significance of dry and wet season forms in some tropical butterflies. Biol J Linn Soc 22: 1-12.

Daniels J. C. 1995. Seasonal variation in the little sulphur butterfly, Eurema lisa lisa, in central Florida: how it compares to other sympatric EuremaHolarctic Lepidoptera 2(2): 59-65). species (Lepidoptera: Pieridae).

Hooper J. 2002. Of the Moths and Men: An Evolutionary Tale. W.W. Norton & Co., 377 p.

Rountree, D. B. & H. F. Nijhout. 1995. Genetic Control of a Seasonal Morph in Precis coenia (Lepidoptera: Nymphalidae). J. Insect Physiol. Vol. 41, No. 12, pp. 1141-1145.

Suzuki, Y. & H. F. Nijhout. 2008. Genetic basis of adaptive evolution of a polyphenism by genetic accommodation. J . Evol. Biol., 21 57–66.

 

 

 

 

Direct competition for nectar in some Patagonian butterflies

Click on the link to download and print pdf of the reference:

Sourakov, A. 2009. Direct competition for nectar in some Patagonian butterflies.  News of Lepidopterists’ Society. 51(1): 14-15.  

Ritual fighting is common among butterflies, but the physical violence is rarely observed.  However, it does occur.  Intraspecific violence has been observed between males of Papilio indra, which are territorial to the extent that they can tear each other to pieces (Eff, 1962).  Physical competition among males for a place on a female pupa is found in Heliconius (e. g., Sourakov, 2008). Males of monarchs and some other butterflies attempt forceful mating with females (e.g., Frey, 1997). 

Here I present an example of apparent physical competition that does not involve sexual selection, but involves interspecific competition for food among three species of Nymphalidae from Patagonia.  In February 2008, I observed how Vanessa terpsichore was repeatedly attacked by Cosmosatyrus leptoneuroides in the southern Andes, Patagonia, Argentina.  Male of the latter butterfly species came repeatedly towards male of V. terpsichorefeeding on a nectar source, which was attractive to many butterflies in the area. Each time, it came into brief physical contact with the feeding butterfly. Similar behavior was exhibited by another nymphalid, Yramea cytheris. I did not observe such behavior on an intraspecific level, though there were many opportunities. Neither attacker was successful in dislodging V. terpsichore from the flowers, although they created sufficient discomfort for it to start flapping its wings.  The photos presented here were created by capturing individual frames from a digital video. Thanks to George Austin for bringing one of the references to my attention.

References

Eff, D. 1992. A little about the little-known Papilio indra minori. J. Lep. Soc. 16(2): 137-142.

Frey D. 1997. Resistance to mating by female monarch butterflies. North American Conference on the Monach Butterfly, Jürgen Hoth (editor). 428 pages.

Sourakov A., 2008. Pupal mating in Zebra longwing (Heliconius charithonia): photographic evidence. News of Lepidopterists’ Society. 50(1): 26-29, 32.