Distribuicao espacial de posturas de Cosmoclopius nigroannulatus Stal (Hemiptera: Reduviidae) em Nicotiana tabacum L. (Solanaceae) | Spatial distribution of Cosmoclopius nigroannulatus Stal (Hemiptera: Reduviidae) egg masses in Nicotiana tabacum L. (Solanaceae)
2003
Jahnke, S.M. | Redaelli, L.R. | Diefenbach, L.M.G. | Efrom, C.F.S.
The search for oviposition sites with good conditions for offspring development is common in many insect species. Predators usually lay eggs in various places in a culture to allow a more complete colonization and to reduce intraspecific competition. This knowledge is important to determine the role of predators in the control of phytophagous populations. The present work aimed at characterizing Cosmoclopius nigroannulatus Stal egg masses in tobacco field, and at identifying their spatial distribution pattern. A field with 270 tobacco plants (Nicotiana tabacum, Virginia type, var. k326), was surveyed from August 1999 to April 2000. The experimental field was located in Porto Alegre, Rio Grande do Sul, Brazil. Each egg mass found had its position recorded in relation to the culture (coordinates), the plant vertical stratum (inferior, middle and apical) and plant structure (steam and leaf). After nymphal emergence, the corions were collected and brought to the laboratory to record the egg number/mass. A total of 176 egg masses were found in 34 sampling occasions. The egg masses dispersion pattern followed a random distribution in almost all occasions, considering both the Dispersion Index I (97%) and the Taylor Power Law Index (b = 0.9633). Most of the eggs (68.4%) were found on the plant apical third. The adaxial leaf side was also preferred for oviposition. The mean number of eggs/mass was 13.1 +/- 4.98, ranging from two to 22. The egg masses distribution pattern in the experimental plot suggests an adequate usage of the available resources.
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