67Anales Instituto Patagonia (Chile), 2007. 35(2): 67-70

Recibido 23/10/2007 Aceptado 5/11/2007

NOTES ON THE BIOLOGY OF DITOMOTARSUS PUNCTIVENTRIS SPINOLA, 1852 (HEMIPTERA: ACANTHOSOMATIDAE) IN THE MAGELLAN REGION,

AND COMMENTS ABOUT THE CRYPSIS IN ACANTHOSOMATIDAE

NOTAS SOBRE LA BIOLOGÍA DE DITOMOTARSUS PUNCTIVENTRIS SPINOLA, 1852 (HEMIPTERA: ACANTHOSOMATIDAE) EN LA REGIÓN DE MAGALLANES,

Y COMENTARIOS ACERCA DE LA CRIPSIS EN ACANTHOSOMATIDAE

Eduardo I. Faúndez1

ANTECEDENTS

Acanthosomatidae is a family of hemiptera for which Kumar (1974), in his worldwide revision, recognizes 45 genera with about 200 species. There is little knowledge about Acanthosomatidae in Chile mainly because most of the data comes from old expeditions, and for many species there are almost not data that can be obtained from their original description; apart from the above, many of them have been mentioned for Chile with locations that currently belong to Argentina, fact that makes it even more difficult the knowledge of these insects because many old authors mention only “Chile” as a general location (Faúndez 2007b).

Ditomotarsus punctiventris Spinola, 1852 was described in Chilean material without specifying location. This species has produced some confusion because it was mistakenly identified as Ditomotar-sus gayi (sensu Signoret 1863) by several authors, situation that was clarified by Bergroth (1917). Regarding its distribution, it is currently known in Argentina and Chile. There are little data on the biology of this species because most of the papers

where it is mentioned are focused on taxonomic and faunistic data; the purpose of this contribution is to provide new data about the sexual behavior, trophic and cryptic habits of this species, and also add comments about evolution of the crypsis in the Acanthosomatidae family.

Observations were made in “Jardín Botánico Carl Skottsberg” belonging to “Instituto de la Patago-nia” (53°08’S-70°53’W; 6 m s.n.m) of “Universidad de Magallanes”, Punta Arenas. Specimens captured in copulation in laboratory were placed inside a small cylindrical glass bottle 11.5 cm tall and 6.5 cm wide. Photographs were taken with a high-resolution digital camera (4mp) and a 3x optical zoom; and for enlarged photographs the same camera was adapted to a stereoscopic microscope.

Trophic niche

The only author that provides data of a host plant for this species is China (1963) who makes reference of it on Senecio smithii DC. (Compositae). In the material examined, mounted with a pin, we have found just one specimen with data of the plant

1 Entomon group, Entomology Laboratory, “Instituto de la Patagonia”, “Universidad de Magallanes”. P.O.Box 113-D. Punta Arenas, Chile, ed.faundez@gmail.com

68 E. FAÚNDEZ

on which it was collected, and it belongs to Berberis microphylla G. Forst. (Berberidaceae).

Examined Material: Punta Arenas, “Tres Puentes” Wetland, IX-2006 col. Felipe Cárcamo, on Magellan Barberry (calafate).

To the data above we can add those data observed where the following was recorded:

At the beginning of the spring specimens have been observed on “ñirre” Nothofagus antarctica (G.Forster) Oersted (Fagaceae) (Fig.2); as the season passes they have also been observed on “zarzapa-rrilla” Ribes magellanicum Poiret (Saxifragaceae) (Fig.3). Specimens stay still on the leaves of both plants; this fact and their green color give them cryptic protection.

In advanced stages of the season, specimens start leaving those plants and are observed in the “ro-maza” Rumex acetosa L. (Polygonaceae) that unlike the plants mentioned above it is native to Europe and Asia and introduced in America (Correa 1984). In this plant, specimens have been observed staying still on the leaves, sucking sap from the stem (Fig.5).

Sexual behavior

Some couples of D. punctiventris were found copulating on R. acetosa, (Fig. 4). More males arrived (up to 5) that got onto the couple trying to mate the female. After some seconds insisting, these harassing males moved away.

Other couples in copulation generally got separated after 15 minutes. As the initial time of copulation was unknown we could not say these times were representative; so more specimens were collected and put inside a small bottle to facilitate observation. In the bottle where two males and one female were put, the following behaviors were recorded:

- Males did not try to copulate with the female until they were near the female inside the small bottle. When the female was at a certain distance they did not come closer.

- When the mating process started, the male got onto the female (at that moment both had their heads pointing towards the same direction), then the male held on the female’s ventral and dorsal part staying suspended from the side of the fema-le. At the same time the male extended its genital structure towards the female, rotating it and trying

to find the female’s genital structures. Once they were coupled, the male located itself at the lateral part of the female, so both stayed with their heads towards opposite directions.

- When they where coupled, another male got onto them trying to mate the female, but it went away after a few seconds, just as it was observed on R. acetosa. Afterwards, this last male was taken out of the bottle, leaving alone the mating couple.

- The first coupling took about 2 hours and 15 minutes. After separating, the male continued trying to mate the female without success. They were separated for about 30 minutes. Afterwards, they coupled again using the same procedure mentioned above. This time the coupling took 1 hour and 10 minutes. After that, they were separated for about 1 hour and 30 minutes, but they coupled for a third time for 1 hour and 57 minutes, repeating the pro-cesses mentioned above to mate. After separating for a third time, they did not mate again, and the specimens were kept in the bottle until the male died the following day.

Comments

Being on different plants could be due to the fact that many of the plants are not available the whole season, making this species to choose different options depending on the season. D. punctiventris is a generalist feeding species that has a wide adap-tive plasticity to the plants it frequents. It has been mentioned from the central part of Chile to Cape Horn archipelago; and in Magallanes it has been related to five host plants pertaining to five different families, and found from wooded environments to wetlands.

Evolution of crypsis in acanthosomatidae

The cryptic coloration in Acanthosomatidae seems to be relatively common, although for most of these species non cryptic habits have been des-cribed. It is almost a fact that most of the “green bugs” (including those of other families of heterop-tera) are cryptic. Although D. punctiventris has cryptic coloration, the great quantity of plants that its frequents does not allow a specialization, making its homocromy to depend much on the amount of light, the part of the plant it is located, and there is

69NOTES ON THE BIOLOGY OF DITOMOTARSUS PUNCTIVENTRIS

Fig. 6. Coupling in D. punctiventris.

Fig. 4. D. punctiventris in copulation on R. acetosa.

Fig. 2. D. punctiventris on N. antarctica.

Fig. 3. D. punctiventris on R. magellanicum.

Fig. 5. D. punctiventris sucking juice in R. acetosa.

General feeder Phytophagous

Specialist Phytophagous

PartialCryptic

TotalCryptic

Fig. 1. Progression of crypsis in Acanthosomatidae.

70 E. FAÚNDEZ

almost not homomorphy. That is why we will call it “partial crypsis”, opposite to what was mentioned for Sinopla perpunctatus Signoret, 1863 with No-thofagus antarctica (G.Forster) Oersted (Fagaceae) by Faúndez (2007a), where the Acanthosomatidae is specialist and its crypsis covers from its immature stages associated to fagaceae: at this status it gets similar to the fruit, and when adult it gets similar to the leaf, existing strong degrees of homocromy and homomorphy. To this type of case we will call it “total crypsis”.

The members of Pentatomorpha are funda-mentally phytophagous (Schaefer 1981). Within them, Acanthosomatidae have phytophagous habits, and this phytophagy would be directly related with crypsis, because it protects them while they are eating. The insects also show specialization from the point of view of the places of feeding that occupy in the plant (Perez-Contreras 1999). In the case of the partial cryptic, apart from having a general status regarding host plants, it is freer in the part of the plant where it sucks juice. An example of this is D. punctiventris in figure 5, while the total cryptic keeps sucking in the part of the plant that gives protection as observed in S. perpunctatus, where the adult sucks juice from the leaves and stems that are near the leaf, so that to be hidden; and the nymph sucks juice from the fruits or the stems that are near the fruit.

Bernays & Chapman (1994) creates a theo-retical example that shows as for an insect general feeder, on different plants, the action of the predators is translated in the selection for the least conspicuo-us, that explain the relationship of the cripsis and the phytophagous habits of the insects, as we can see in this case. Thus, we conclude that crypsis in acanthosomatidae comes up as a useful protection during feeding of insects, with a progression going from a general feeder phytophagous which starts with a partial crypsis to turn into a specialist with a total crypsis (Fig. 1).

ACKNOWLEDGEMENTS

I thank my professor Vicente Pérez D’Angello for making a critical reading of the text, and to Dr. Juan M. Henríquez for the identification of R. acetosa L.

LITERATURE CITED

Bergroth, E. 1917. New and little known Heteropte-rous Hemiptera in the United States National Museum. Proceedings of the U.S. National Museum. 51(2150): 215-239.

Bernays, E.A. & R.F. Chapman 1994. Host-Plant Selection by Phytophagous Insects. Chapman and Hall, New York. 312pp.

China, W.E. 1963. Hemiptera-Heteroptera collected by the Royal Society expedition to South Chile 1958-1959. Annals and Magazine of Natural History. (13)5[1962]:705-723.

Correa, M. 1984. Flora Patagónica. Tomo VIII, Parte IV. Buenos Aires. 559 pp.

Faúndez, E. I. 2007a. Asociación críptica en-tre Sinopla perpunctatus Signoret, 1863 (Acanthosomatidae: Hemiptera) y el Ñirre Nothofagus antarctica (G. Forster) Oersted (Fagaceae) en la Región de Magallanes (Chile). Boletín Sociedad Entomológica Aragonesa. 40:563-564.

Faúndez, E. I. 2007b. Lista de las especies de Acanthosomatidae (Insecta: Hemiptera) de la región de Magallanes (Chile). Anales Instituto Patagonia (Chile). 35(1): 75-78.

Kumar, R. 1974. A revision of world Acanthosomati-dae (Heteroptera: Pentatomoidea): Keys to and descriptions of subfamilies, tribes and genera, with designation of types. Australian Journal of Zoology, Suppl. Ser. N° 34:1-60.

Pérez-Contreras, T. 1999. La especialización en insectos fitófagos: una regla más que una excepción. Boletín Sociedad Entomológica Aragonesa. 26: 759-776.

Schaefer, C.W. 1981. The land bugs (Hemiptera: Heteroptera) and their adaptative zones. Rostria. 33 Suppl. : 67-83.

Signoret, V. 1863. Révision des Hémiptères du Chili. Annales de la Société Entomologique de France. (4)3:541-588.

Spinola, M. 1852. Hemípteros. in: Gay, C. Historia física y política de Chile. Zoología. Vol. 7: 113-320 Paris.