Megacopta cribraria ( Fabricius 1798 )

J. E. Eger, Jr., Ames, M., Suiter, D. R., Jenkins, T. M., Rider, D. A. & Halbert, S. E., 2010, Occurrence of the Old World bug Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae) in Georgia: a serious home invader and potential legume pest, Insecta Mundi 2010 (121), pp. 1-11 : 2-7

Megacopta cribraria ( Fabricius 1798)

Figure 1-4 .

Cimex cribraria Fabricius, 1798: 531 .

Tetyra cribraria: Fabricius 1803: 143 .

Thyreocoris cribarius [sic]: Burmeister 1835: 384.

Coptosoma cribrarium: Amyot and Serville 1843: 66 , pl. 2, fig. 4.

Coptosoma xanthochlora Walker, 1867: 87 (Synonymized by Distant 1899).

Megacopta cribraria: Hsiao and Ren 1977: 21-22 , 293, figs. 62, 69, 70, pl. 1, fig. 13.

Diagnosis. Small round species, 3.5 to 6.0 mm long; light brown to olive green with dark punctation ( Fig. 1 ). Head flat, juga contiguous in front of tylus; second antennal segment one-third or less length of third segment. Tarsi two-segmented; tibiae setose, lacking stout spines. Scutellum enlarged, width nearly 1.5 times length, truncate or very broadly rounded posteriorly, widest on posterior fourth; base of scutellum with transversely elongate area outlined by distinct impressed line. Venter black, moderately punctate; females with broad pale area laterally on abdomen ( Fig. 2 ), males with broad pale lateral area limited to second and third visible sternites, segments 4-6 black and densely setose laterally ( Fig. 3 ). Fifth-instar nymphs 4-5 mm long, oval, light to dark brown, hirsute; lateral margins of thorax and abdomen somewhat flattened ( Fig. 4 ).

Comments. Among North American Pentatomoidea, this bug is readily distinguished by the two-segmented tarsi and enlarged scutellum that is widest near the posterior margin and relatively truncate posteriorly. Other groups in which the scutellum is enlarged ( Scutelleridae , Thyreocoridae , Pentatomidae : Asopinae and Podopinae ) have three-segmented tarsi and the posterior margin of the scutellum is more narrowly rounded. Two-segmented tarsi also occur in the family Acanthosomatidae , but North American species of this family have a small triangular scutellum.

Megacopta cribraria , described by Fabricius (1798) as Cimex cribrarius , was later transferred to the genus Coptosoma (Laporte) by Amyot and Serville (1843). Hsiao and Ren (1977) transferred it to their new genus, Megacopta , where it remains today. Montandon (1896) described a closely related species, M. punctatissima (as Coptosoma punctatissimum ). The following year, Montandon (1897) reported that he had seen specimens that were intermediate between M. cribraria and M. punctatissima but did not formally synonymize the two species. Yang (1934) revised the Chinese species of Plataspidae and considered M. punctatissima to be a variety of M. cribraria . Both names continue to be used today; however, primarily in Japanese economic literature (e.g. Hasegawa 1965, Hibino and Ito 1983, Himuro et al. 2006, Hirashima 1989, Imura 2003, Ishihara 1950, etc.). In fact, Hosokawa et al. (2007) stated that Megacopta punctatissima is found in mainland Japan and is a frequent pest of soybeans, whereas M. cribraria is found in the southwestern Japanese islands, rarely causes agricultural problems and is considered harmless to soybeans. They also indicated that the two species are capable of interbreeding and that their offspring reproduce successfully. These two taxa are distinguished primarily by color and size, M. punctatissima supposedly being darker and a little larger than M. cribraria . There appears to be no difference in morphology and the genitalia are indistinguishable. Specimens from Georgia are variable in size and fall within the range of coloration seen in museum specimens of M. cribraria . In addition, Jenkins et al. (2010) found that molecular characters for Georgia specimens are similar to those previously reported for M. cribraria . Although there appears to be some disagreement with regard to the taxonomic status of M. punctatissima , we are confident that the species found in Georgia is M. cribraria . Common names that have been used for this bug include bean plataspid, lablab bug, and globular stink bug.

Females of M. cribraria and related species of Plataspidae deposit small brown capsules on the underside of the egg masses. These capsules contain gut symbiotic bacteria ((-Proteobacterium Candidatus Ishikawaella capsulata) ( Fukatsu and Hosokawa 2002, Hosokawa et al. 2006). As mentioned previously, Hosokawa et al. (2007) reported that M. punctatissima is a pest of soybeans whereas crop legumes are not suitable hosts for M. cribraria . When these authors transferred symbiotic bacteria from the ‘pest’ species M. punctatissima to the ‘non-pest’ species M. cribraria , soybeans became a suitable host for the latter species. Thus, differences between these two ‘species’ of Megacopta may be attributed to the symbiotic bacteria. Jenkins et al. (2010) confirmed the presence of this bacterial symbiont in bugs collected in Georgia.

Because M. cribraria and M. punctatissima are closely related and likely conspecific, the following sections contain information on both ‘species.’ Reports from Japanese authors usually refer to M. punctatissima , whereas all others refer to M. cribraria .

Distribution Megacopta spp. have been reported from Australia, China, India, Indonesia, Japan, Korea, Macao, Malaysia, Myanmar, New Caledonia, Pakistan, Sri Lanka, Taiwan, Thailand and Vietnam ( Montandon 1896, 1897; Distant 1902; Kirkaldy 1910; Matsumura 1910; Shroff 1920; Esaki 1926; Hoffman 1931, 1935; Yang 1934; Ishihara 1937; Esaki and Ishihara 1951; Ahmad and Moizuddin 1975; Hsiao and Ren 1977; Lal 1980; Ren 1984; Hirashima 1989; Easton and Pun 1997). Prior to this discovery in Georgia, the family Plataspidae was restricted to the Old World ( Froeschner 1984).

Host Plants and Pest Status Megacopta spp. have been reported most commonly from legumes ( Fabaceae ). Table 1 lists the leguminous plants reported as hosts for these bugs. Many of these are reported by multiple authors and numerous additional references to kudzu and soybean could be added. Additional references simply stated that these bugs feed on legumes, confirming that legumes are evidently the primary hosts of Megacopta spp. Non-leguminous hosts reported for Megacopta spp. are given in Table 2. Few are given by more than one author and those references that provided data on abundance or life stages for non-leguminous plants generally listed Megacopta spp. as uncommon or rare and the life stage encountered was usually adults. Most of these records probably represent incidental collections. However, Srinivasaperumal et al. (1992) report that M. cribraria survived and reproduced on firecracker plant, Crossandra infundibuliformis (L.) Nees ( Acanthaceae ) and cotton, Gossypium hirsutum L. ( Malvaceae ). Nymphs took longer to complete development and female fecundity was lower on these plants than on the legume Sesbania grandiflora (L.) Pers., but M. cribraria was able to complete development on these two non-legume plants.

Many of the host records in Tables 1 and 2 are simply records of Megacopta spp. on the plant and do not indicate pest status. Ahmad and Moizuddin (1975), Rekha and Mallapur (2007), Sujithra et al. (2008), Thejaswi et al. (2008) and Thippeswamy and Rajagopal (1998) reported that M. cribraria is a pest of field or lablab bean, whereas Ramakrishna Ayyar (1913) and Srinivasaperumal et al. (1992) stated that it was a serious pest on Sesbania spp. Hasegawa (1965), Lal (1980), Ren (1984), and Yang (1934) reported that Megacopta spp. are pests of legumes in general. A number of authors report that Megacopta spp. are pests of soybeans ( Hosokawa et al. 2007, Ishihara 1950, Kobayashi 1981, Kono 1990, Wang et al. 1996, Wu and Xu 2002, and Xing et al 2008). Soybean yield loss ranged from 1-50% depending on density of the bugs ( Wang et al. 1996). The reported pest status ranges from minor to severe. As an introduced species, this bug appears to have potential to be a pest of legume crops in the United States.

Megacopta spp. have also been investigated as a potential biological control agents for kudzu ( Sun et al. 2006, Tayutivutikul and Kusigemati 1992 a, Tayutivutikul and Yano 1990). Ishihara (1950) reported that kudzu is the preferred host for this species. However, there is no record of Megacopta spp. being imported to the U.S. for classical biological control of kudzu.

Thippeswamy and Rajagopal (2005b) reported that M. cribraria feeds on leaves, stems, flowers and pods, but prefers tender new growth to older growth. They also noted that white ‘patches’ developed at the site of feeding and later turned brownish, gradually coalescing into a necrotic area and that shoots withered with heavy infestations and bean pods did not develop normally.

Development The reported numbers of eggs deposited by females of Megacopta spp. ranged from 26 to 274; the development time from egg to adult was 24 to 56 days; and adult longevity was 23 to 77 days, depending on location, temperature and other conditions ( Ahmad and Moizuddin 1977, Ramakrishna Ayyar 1913, Srinivasaperumal et al. 1992, Tayutivutikul and Kusigemati 1992b, Tayutivutikul and Yano 1990, Thippeswamy and Rajagopal 2005b). There are one to three generations a year in China and Japan and Megacopta spp. overwinter as adults ( Hibino and Ito 1983, Tayutivutikul and Kusigemati 1992b, Wu et al. 2006). Moizuddin and Ahmad (1979) described, figured and keyed the different immature stages of M. cribraria .

Megacopta spp. colonize crop fields in April to July and are present until August to October, depending on location and crop ( Hibino and Ito 1983, Takagi and Murakami 1997, Tayutivutikul and Yano 1990, Thejaswi et al. 2008). In warmer areas, they may be active all year ( Thippeswamy and Rajagopal 1998). Large mating aggregations are common and females tend to accept copulation more frequently when males court in aggregations than when they court alone ( Hibino 1985, 1986, 1989, Hibino and Ito 1983).

Natural Enemies Ahmad and Moizuddin (1976) reported Reduviius [sic!] sp. ( Heteroptera : Reduviidae ) feeding on adults and fifth-instar nymphs of M. cribraria . Parasitoids ( Hymenoptera ) reported from eggs of Megacopta spp. were Ablerus sp. (Aphelinidae) in India ( Rajmohan and Narendran 2001); Dirphys boswelli (Girault) (Aphelinidae) in India ( Polaszek and Hayat 1990); Ooencyrtus nezarae Ishi (Encyrtidae) in China and Japan ( Hirose et al. 1996, Takasu and Hirose 1991a, 1991b, Tayutivutikul and Yano 1990, Wu et al. 2006); Ooencyrtus sp. (Encyrtidae) and Trissolcus sp. (Scelionidae) in China ( Zhang et al. 2003); Paratelenomus saccharalis (Dodd) (Scelionidae) in China, India and Japan, ( Hirose et al. 1996, Rajmohan and Narendran 2001, Takagi and Murakami 1997, Wall 1928, Watanabe 1954, Wu et al. 2006, Yamagishi 1990); Telenomus latisculcus Crawford (Scelionidae) in India ( Mani and Sharma 1982); and Telenomus sp. (Scelionidae) in Pakistan ( Ahmad and Moizuddin 1976). Synonyms for P. saccharalis are Asolcus minor (Watanabe) , Archiphanurus minor and Paratelenomus minor ( Johnson 1996) . Borah and Dutta (2002) and Borah and Sarma (2009) reported that the fungal pathogen Beauveria bassiana (Balsamo) Vuillemin attacks M. cribraria in India.

The large numbers of M. cribraria found on kudzu suggests that this bug may provide some biological control of kudzu. The tendency of M. cribraria to aggregate on and in houses suggests that it may become an even greater household pest. Because there are few crops in the area around the current infestation, the potential impact of this species on crops in the United States is unknown. Continued surveillance to determine the distribution and spread of M. cribraria is needed, as is research to determine the host range of the population in Georgia and the efficacy of various control measures.

Figures

Figure 1-4. Megacopta cribraria. 1) Male, dorsal view. 2) Female, ventral view. 3) Male, ventral view. 4) Fifth instar nymph, dorsal view. Dimensional line equals 1.0 mm.