Oviposition and Development in Gregopimpla Kuwanae Viereck (Hymenoptera: Ichneumonidae), a Gregarious Ectoparasitoid Wasp Attacking the Rice Skipper Parnara Guttata
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Hindawi Publishing Corporation Journal of Insects Volume 2016, Article ID 4706376, 8 pages http://dx.doi.org/10.1155/2016/4706376 Research Article Oviposition and Development in Gregopimpla kuwanae Viereck (Hymenoptera: Ichneumonidae), a Gregarious Ectoparasitoid Wasp Attacking the Rice Skipper Parnara guttata Takatoshi Ueno Institute of Biological Control, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan Correspondence should be addressed to Takatoshi Ueno; [email protected] Received 16 November 2015; Revised 13 January 2016; Accepted 13 January 2016 Academic Editor: Francisco de Sousa Ramalho Copyright © 2016 Takatoshi Ueno. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Gregopimpla kuwanae is a gregarious ectoparasitoid wasp attacking mature larvae and prepupae of the rice skipper Parnara guttata (Lepidoptera: Hesperiidae), a major herbivorous pest in rice paddies. Here, the biology of G. kuwanae was investigated using Galle- ria mellonella as a laboratory host. Adult females accepted G. mellonella cocoons for oviposition, and larvae of G. kuwanae developed successfully to adulthood on this host. Females laid, on average, 3.5 eggs per host. Time required for oviposition was relatively long (mean = 14.2 min). Survival of parasitoid offspring decreased with the increasing number of eggs on each host. Females used 18.9% of hosts for host feeding, killing the hosts with no exception. Oviposition did not occur on hosts used for feeding purpose, indicating that the parasitoid was a nonconcurrent, destructive host feeder. Newly emerging adult females carried no eggs in the ovary; females started oogenesis only after they had destructively fed on hosts. This parasitoid thus was extremely synovigenic (ovigeny index = 0). Gregopimpla kuwanae laid typically yolk-rich, anhydropic eggs. Females carried on average 15 mature eggs with 20 immature eggs, and larger females had a greater number of eggs in the ovary. Life history characteristics of G. kuwanae were discussed. 1. Introduction particular insect species or groups as indicator organisms for extensive studies [3, 9, 10]. At least, candidate species or Growing attention has been paid to the role of agricultural groups should be widely distributed, commonly found, read- fields to support biodiversity and the role of agrobiodiver- ily recognized or sampled, sensitive to agricultural practices, sity including beneficial pollinators and natural enemies as and easily reared in the laboratory. It is also ideal if indicator elements on sustainable production in agriculture [1–5]. Rice organisms reflect the level of biodiversity in agricultural land. paddies support one of the largest insect communities among Insect parasitoids are among beneficial organisms, and agricultural systems in Asia [6, 7]. Insect community in rice many parasitoids have been recorded from rice paddies [11]. paddies includes a variety of natural enemies that help control Most parasitoids in rice paddies are associated with lepi- of rice pests [8, 9]. Environmentally benign rice production dopteran and homopteran rice pests [12–15]. The rice skipper should therefore apply farming practices that could be least Parnara guttata (Bremer et Grey) is a major herbivorous rice influential to the natural enemies, including parasitoids and pest in Japan [15, 16]. Because P. g ut tata larvae make leaf rolls, predators, to enhance biological pest control. Such practices which are visibly conspicuous, it is easy to sample this pest, mayalsohelpconserveagrobiodiversityinricepaddies. and therefore parasitoids associated with P. g ut tata can easily In addition, it is required to establish laboratory systems be sampled. for assessing the effects of farming practices, for example, Gregopimpla kuwanae Viereck (Hymenoptera: Ichneu- agrochemical application. Given that rice paddies provide monidae) has frequently been found as a gregarious ectopar- habitats for hundreds of beneficial insect species [6–8], all asitoid of P. g ut tata [15,17,18],thoughitisalsoknownasan of these insects would be difficult to be involved in the important natural enemy of the silver Y moth Autographa abovementioned studies. Accordingly, it is necessary to select gamma (L.) [19]. Gregopimpla kuwanae is common and 2 Journal of Insects is widely distributed in Japan and East Asia [17] and is The observation was made to assess whether G. mellonella relatively large in size (forewing length: 5–10 mm) [18]. Given was selected by G. kuwanae as an oviposition site. Cocoons its commonness in rice paddies and easiness to sample, G. containing prepupae of G. mellonella were presented singly kuwanae is a candidate indicator organism. However, it is to female parasitoids, and their response to the cocoons was not known whether the parasitoid can easily be reared in directly observed. Each female was continuously observed the laboratory. Also, its detailed biology is not known. The for the first 15–20 min. When females did not respond to present study was thus undertaken to test the easiness of a host during this observational period, the host was kept rearing G. kuwanae andtorevealthebasicbiology. left in the container for 3–5 hours with the same females Because the natural host P. g ut tata is difficult to mass- and was examined about every hour to confirm whether it rear, it is desirable to use laboratory hosts for the rearing was attacked or not. Host cocoons were dissected to confirm system. Many previous literatures suggest that the greater wax whether parasitoid eggs were present on host body surface. moth Galleria mellonella (L.) is widely suitable for rearing In all, 6 wild-caught females of unknown age, 12 females ichneumonid parasitoids [20–22]. In addition, G. mellonella that emerged from wild-caught P. g ut tata ,and10laboratory- can be easily reared on artificial diets. If it is possible to rear G. reared females that emerged from G. mellonella were used. kuwanae on this host, laboratory testing like insecticide effect Except for wild-caught females, mated female parasitoids evaluation will be greatly promoted. aged 0–4 days were used. The observations were made at ∘ Here, I first examined suitability of G. mellonella as a lab- room temperature around 26 C. oratory host of G. kuwanae. Second, the oviposition behavior wasobservedtoinvestigatelifehistoryandreproductive 2.3. Oviposition. The oviposition behavior of G. kuwanae on characteristics of G. kuwanae. Specifically, the present study the laboratory host G. mellonella was observed. As a pre- examined host acceptance, clutch size (how many eggs a experimental treatment, individual females for testing were female laid on each host cocoon), and offspring survival on G. provided with two host cocoons after emergence. The two mellonella. Third, dissection experiments were conducted to host cocoons were left in contact with the female parasitoid assess fecundity and reproductive mode of G. kuwanae (i.e., for one day and were replaced with fresh cocoons every synovigenic or proovigenic). Such information would help day. All host cocoons were dissected to examine whether the understand the reproductive characteristics of G. kuwanae. females oviposited on them. These treatments ensured all test Based on these results, laboratory rearing and life history of females respond to the laboratory host, thus enabling the G. kuwanae are discussed. following observation. Oviposition behavior and clutch size were examined 2. Materials and Methods using mated females of 5-6 days old that had at least oviposited on one host. Host cocoons were singly offered to 2.1. Parasitoid and Host. A laboratory colony of G. kuwanae individual females in the container. When females mounted was established using adult parasitoids collected from rice hosts, their responses to the hosts were directly observed paddies in Tsukuba, central Japan. Adults that had emerged (i.e., host rejection, ovipositor insertion, oviposition, and host from P. g ut tata collected from rice fields in Tsukuba were also feeding). Hosts were removed from the container immedi- used to establish the colony. Female parasitoids were placed ately after the females had left the hosts. By doing so, multiple individually in plastic containers (10 cm in diameter, 4.5 cm attacks on each host were avoided. Time taken for oviposition in height), together with tissue paper saturated with diluted was measured. Host cocoons that had been parasitized or fed honey. The tissue paper was replaced twice a week thereafter. upon were carefully dissected. With the aid of fine scissors, ∘ The containers were kept at 20 ± 0.5 C under a photoperiod cocoons were longitudinally cut and opened, and the number of 16L : 8D. of eggs laid was counted. Host cocoons dissected were then The colony was maintained on prepupae of a laboratory wrappedcarefullywithtissuepaperandusedinthefollowing host, G. mellonella. Host cocoons containing prepupae were experiment. This treatment itself did not affect the successful presented to female G. kuwanae in the plastic containers. pupation of unparasitized hosts. Also, preliminary observa- ∘ Parasitized hosts were removed and held at 20 ± 0.5 C under tions suggested offspring parasitoid survival was not affected a photoperiod of 16L : 8D until parasitoid emergence. Newly if host cocoons once opened were wrapped as mentioned emerging parasitoids were individually placed