LI TAO¹, SHENG MAO-LING², SUN SHU-PING³, CHEN GUO-FA⁴ and GUO ZHI-HONG⁵

¹ Ph. D. The Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry University, Beijing 100083, P. R. China; General Station of Forest Pest Management, State Forestry Administration, No. 58 Huanghe North Street, Shenyang 110034, P. R. China, litao200105@163.com
² Ph. D. General Station of Forest Pest Management, State Forestry Administration, No. 58 Huanghe North Street, Shenyang 110034, P. R. China, shengmaoling@163.com, corresponding author.
³ M. Sc. General Station of Forest Pest Management, State Forestry Administration, No. 58 Huanghe North Street, Shenyang 11003
⁴, P. R. China, sfzzssp@163.com 4 M. Sc. General Station of Forest Pest Management, State Forestry Administration, No. 58 Huanghe North
Street, Shenyang 110034, P. R. China, guofachen@yahoo.com
⁵ M. Sc. General Statio

Received: 24-Apr-2011 - Accepted: 22-Oct-2012

Abstract: The responses of adult ichneumonids to colors were studied through comparing the effectiveness of standardized interception traps in seven different colors, in Liupanshan, Daxinggou and Xinbin (China). The captured ichneumonids belonged to 13 subfamilies: Anomaloninae, Banchinae, Campopleginae, Cryptinae, Ctenopelmatinae, Diplazontinae, Ichneumoninae, Mesochorinae, Ophioninae, Orthocentrinae, Phrudinae, Pimplinae, and Tryphoninae. Field trapping results indicated that yellow and green traps collected more ichneumonids than did the traps of other colors. Black was the least efficient color for collecting ichneumonids in Liupanshan and Xinbin. The most frequently collected specimens were from the subfamilies Ctenopelmatinae, Campopleginae and Cryptinae, while the least frequently collected were from Phrudinae, Ophioninae and Diplazontinae in Liupanshan and Xinbin. In Daxinggou, black and yellow traps collected more ichneumonids than did other color traps, with white traps collecting the least. Most captured ichneumonids at this site were from Campopleginae and Cryptinae, whereas only a small number of specimens were collected from Banchinae, Phrudinae, Ophioninae and Diplazontinae were collected.

Key words: Ichneumonidae. Parasitoid. Color. Trapping efficiency. Interception traps.

Resumen: Se compararon las respuestas de ichneumónidos adultos ante trampas con colores, medidas por la eficiencia de trampas estandarizadas de intercepción con siete colores diferentes, en Liupanshan, Daxinggou y Xinbin (China). Los ichneumónidos capturados se agruparon en 13 subfamilias: Anomaloninae, Banchinae, Campopleginae, Cryptinae, Ctenopelmatinae, Diplazontinae, Ichneumoninae, Mesochorinae, Ophioninae, Orthocentrinae, Phrudinae, Pimplinae y Tryphoninae. Los resultados del trampeo en campo revelan que las trampas amarillas y verdes atraparon más ichneumónidos que las de otros colores. El negro fue el color menos eficiente en la colecta de ichneumónidos en Liupanshan y Xinbin. En esta ciudades, los especímenes más frecuentemente colectados pertenecían a las subfamilias Ctenopelmatinae, Campopleginae y Cryptinae, mientras que los de Phrudinae, Ophioninae y Diplazontinae fueron los de menor colecta. Sin embargo, en Daxinggou, las trampas negras y amarillas atraparon más ichneumónidos que las de otros colores. En este sitio las trampas blancas fueron las menos efectivas. La mayoría de las capturas en este sitio fueron Campopleginae y Cryptinae, mientras que una pequeña fracción de especímenes lo fue de las subfamilias Banchinae, Phrudinae, Ophioninae y Diplazontinae.

Palabras clave: Ichneumonidae. Parasitoides. Color. Eficiencia de trampeo. Trampas de intercepción.

The vision of parasitoid wasps plays an important role in locating a host, mating, avoiding predators and searching for an oviposition site (Land 1997; Raine and Chittka 2007). Parasitoid wasps can find hosts by distinguishing the color or shape of hosts or host habitat (as well as by various olfactory signals) (Brown et al. 1998; Fischer et al. 2004; Segura et al. 2007). Itoplectis conquisitor (Say) (Hymenoptera: Ichneumonidae) can learn the characteristics of light reflected by artificial host microhabitats (Arthur 1966).

Insects have different types of photoreceptors that can detect different wavelengths of light, such as green, blue and UV light. Some hymenopterans not only can detect colors at 340 nm, 430 nm, and 535 nm, but also can detect those of long wavelengths up to 600 nm (Hardie 1986; Peitsch et al. 1992; Briscoe and Chittka 2001). The capture of insects in traps is influenced by the insect sensitivity to different colors among other variables. Based on these characteristics, entomologists use passive and active traps to collect insects. Malaise traps are widely used interception traps for catching flying insects, especially Diptera and Hymenoptera (Nieves-Aldrey and Rey del Castillo 1991; Steinbauer et al. 2000; Ganho and Marinoni 2003). These traps have also been extensively used for collecting Ichneumonidae (Townes 1962, 1972; Darling and Packer 1988; Anento and Selfa 1997; Skillen et al. 2000; Kumagai and Graf 2002; Sääksjärvi et al. 2004; Mazón and Bordera 2008).

Ichneumonidae is the largest family within Hymenoptera, which is probably the most diverse order in the world (Grissell 1999). Townes (1969) estimated that there could be about 60,000 ichneumonid species in the world whilst Gauld (1997) revised this figure upwards to potentially more than 100,000 species. They can be highly significant in suppressing populations of holometabolous pest insects and an important component in all terrestrial ecosystems. In order to better understand the biodiversity and population dynamics of Ichneumonidae in forest ecosystems, we carried out a comparative field trapping study using an improved interceptive trap on the effect of trap color on the captures of ichneumonids in Liupanshan, Ningxia Hui Autonomous Region, Daxinggou, Jilin Province and Xinbin, Liaoning Province, P. R. China.

Experimental sites. Field trapping experiments were conducted in the forests located at following three locations: Liupanshan, Xinbin and Daxinggou.

Liupanshan site is located at Liupanshan Mountains, in the border region of southwest Ningxia Hui Autonomous Region, east Gansu Province and west Shaanxi Province, which is the natural ecological shelter and water source areas of the western Loess Plateau, and plays an important role in eco-environmental conservation. The forest coverage rate reaches up to 72.8%, with a 5.8 °C annual mean temperature and 676 mm annual mean precipitation. The forest stand is composed of mixed deciduous angiosperms and evergreen conifers, mainly Pinus tabulaeformis Carr., Hippophae rhamnoides L., Elaeagnus angustifolia L. and Caragana korshinskii Kom.

Statistical analysis. Trap catch data (numbers of ichneumonids per trap per week) were transformed by log (x + 1) and analyzed by one-way ANOVA, followed by the Ryan-Einot-Gabriel-Welsh (REGW) multiple Q test (SPSS 17.0 for windows) at α = 0.05.

All specimens of ichneumonids were identified to subfamily level. Most trapped ichneumonids belong to following 13 subfamilies: Anomaloninae, Banchinae, Campopleginae, Cryptinae, Ctenopelmatinae, Diplazontinae, Ichneumoninae, Mesochorinae, Ophioninae, Orthocentrinae, Phrudinae, Pimplinae, Tryphoninae.

In Liupanshan site, green traps caught the highest numbers of ichneumonids, with an average of 168 per week (N = 17). Black traps were less successful with an average of just two ichneumonids per week (N = 17). There were no significant differences in ichneumonid catches between green and yellow traps (F = 43.97; df = 6, 112; P > 0.05), but both caught significantly more attractive than did the other color traps (P < 0.001). The blue traps caught only a few individuals but were still statistically higher than black traps (Fig. 2).

The number of ichneumonids at subfamily level captured in the three most attractive color traps (black, yellow and green) from each site were further analyzed (Figs. 3-5). There were significant differences in the trapping efficiency to different ichneumonid subfamilies among these three color traps.

In Liupanshan, Ctenopelmatinae, Campopleginae, Cryp­tinae, Orthocentrinae and Mesochorinae were the major subfamilies, there were no significant differences among these five subfamilies by green traps and there were no significant differences among Ctenopelmatinae, Campopleginae, Cryptinae and Mesochorinae by yellow traps (F = 22.76; df = 12, 208; P > 0.05) (Fig. 3). The numbers of ichnuemonids from Ctenopelmatinae, Campopleginae and Cryptinae seemed to be significantly higher than most of the minor subfamily group for both green and yellow traps (P < 0.001). There were only a few individuals of ichneumonids caught in the black traps at this site with Cryptinae, Ctenopelmatinae and Ichneumoninae being the key subfamilies. No specimens from the following subfamilies were collected in the black traps: Anomaloninae, Diplazontinae, Mesochorinae, Orthocentrinae, Pimplinae and Tryphoninae.

In Xinbin, Cryptinae and Campopleginae were two major subfamilies caught by yellow, green and black traps, and there were no significant differences between these subfamilies (F = 8.94; df = 12, 195; P > 0.05), but both caught significantly more richness than Ctenopelmatinae (P < 0.001) (Fig. 4). No specimens from following subfamilies: Diplazontinae, Tersilochinae, Pimplinae and Banchinae, were captured by black color traps, and only a few individuals of them were collected from the green and yellow traps.

Different insect families show preferences for different trap colors. Hoback et al. (1999) published a list of insect families with their preferences for different trap colors. Most insects that have been examined prefer yellow traps (Prokopy and Owens 1983). Farmland sawflies showed strong responses to colored traps, especially to yellow ones (Barker et al. 1997). Yellow is a strong innately preferred color by female Venturia canescens Gravenhorst, 1829 (Hymenoptera: Ichneumonidae) over orange and blue (Lucchetta et al. 2008).

In our study, the capture efficiency of color interception traps for ichneumonids were evaluated. Yellow and green proved to be much better than other colors in collecting ichneumonids and black was the less successful color in Liupanshan and Xinbin. However, there was a strong variation among sites: the least attractive color, black, in the above mentioned two sites, was the most attractive one at Daxinggou site. The real causes for such geographical (site) variations are unknown; however, differences in local microhabitats, forest stand structures and ichneumonid fauna might contribute to the disparity in color preference. Ctenopelmatinae, Campopleginae and Cryptinae were the most common subfamilies in Liupanshan. The latter two were also the most dominant subfamilies in Xinbin and Daxinggou. The diversity and relative abundance of the ichneumonids at subfamily level might be closely related to local habitat types. At Liupanshan site, the main vegetations are shrubs and pine plantations with coverage up to 95% of the ground area, suggesting a better environment and higher abundance of insects. Traps in Liupshan caught more ichneumonids in total than those in the other sites. In Xinbin and Daxinggou, the main vegetations are oak forests and coniferous forests respectively, with less insect biomass overall and fewer ichneumonids caught. Woodlands play an important role in the maintenance of biodiversity of parasitoids (Fraser et al. 2007). The response of ichneumonids to yellow, green and black color traps need further investigation.

Species belonging to the subfamilies Rhyssinae, Poemeniinae and Metopiinae are commonly found in the study areas but only a few specimens were captured by the interception traps. It might be due to the fact that these groups of ichneumonids are not strongly attracted to colors.

We are especially grateful to Dr. Gavin R. Broad (The Natural History Museum, London, UK) and Dr. Qing-He Zhang (Sterling International, Inc., USA) for their valuable comments and suggestions. We are thankful to two anonymous referees for their criticism and important suggestions. We also want to express our sincere gratitude to Xiao-Ren Xu, Feng-Cai He, Li-Xia Song and Shu-Feng Pan for their help in the course of field experiments. This project was funded by the National Natural Science Foundation of China (NSFC, No. 30872035; No. 31010103057).

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