Scientific name - Taxonomic position - Diagnosis - Images - Distribution - Biology / Hosts - References

Scientific name

Quadrastichus erythrinae Kim 

Taxonomic position

Hymenoptera: Chalcidoidea: Eulophidae: Tetrastichinae

Diagnosis

Adults exhibit marked sexual dimorphism. Female 1.4–1.6 mm long, dark brown with yellow markings; head yellow except gena posteriorly brown; antenna pale brown except scape pale posteriorly; pronotum dark brown; midlobe of mesoscutum with an anterior V-shaped or inverted triangular dark brown marking, posteriorly yellow, scutellum and dorsellum light to dark brown, legs pale except fore- and hind coxae brown, fore- and mid-femora ventrally brown, pretarsi dark brown; metasoma (gaster / abdomen) brown to dark brown, anteriorly slightly paler. Antenna with one large anellus, three funicular segments, all longer than broad. Metasoma longer than head+mesosoma. Fore wing with one seta on submarginal vein, situated slightly basad of middle, postmarginal vein rudimentary.

Male smaller than female, 1.0–1.2 mm long, ground colour pale white to creamy yellow, pronotum dark brown, mesoscutum medially dark brown in anterior  half, scutellum and dorsellum brown, metasoma pale in anterior half, posteriorly dark brownish, legs entirely pale. Antenna with four funicular segments, F1 much shorter than rest and transverse, other segments distinctly longer than broad, ventral plaque of scape situated in apical half.

Images

          

Larvae of Q. erythrinae inside the galls     

       

Larva of Q. erythrinae 

       

Pupa of Q. erythrinae - ventral and dorsal view

          

Male and female, lateral view      Female, dorsal view                       Male, dorsal view

       

Adult female - dorsal view

       

Adult male - dorsal view

            

Galls on erythrina formed by Q. erythrinae 

               

Adult emergence holes on leaf galls

Distribution

The wasp is of East African origin and it naturally occurs in Tanzania, where it has got a complex of natural enemies which have potential for biological control of this pest.  Related species of Quadrastichus which induce galls in eucalyptus occur throughout subtropical Africa. It was first identified in 2002 from Singapore and Mauritius and has since then spread rapidly to several countries including the Reunion islands, Taiwan, India, Thailand, Hawaii, Hong Kong, China,  Okinawa, the Philippines, USA (Florida),Guam, and American Samoa (Prinsloo & Kelly, 2009). From India, it was first recorded from Kerala (Faizal et al., 2006) and later from Karnataka and Tamil Nadu.

Biology / Hosts

The erythrina gall wasp forms galls on the leaves, stems, petioles, and young shoots of Erythrina spp. ("coral tree"), with at least five species known to be affected. In southern India, it has been reported to damage Erythrina stricta Roxb., a commonly used live standard for pepper and vanilla in plantations. As galls are formed on the newly emerging leaves, there is severe reduction in the number and size of leaves besides complete cessation of growth. Inside the leaf galls there is usually only one wasp per cell, whereas in the swollen tissues of shoots, twigs and petioles, more than five individuals are present (Kim et al., 2004). Affected trees appear to be scrawny with malformed and crinkled shoots, suffer severe defoliation and ultimately die (Faizal et al., 2006).  

Recent efforts to identify the natural enemies of the erythrina gall wasp have led to the discovery of at least 12 species of chalcidoids, mostly eulophids, in association with erythrina galls in West and East Africa (Prinsloo & Kelly, 2009). From South Africa, Prinsloo & Kelly (2009) identified five new tetrastichine species, namely, Quadrastichus ingens, Q. gallicola, Q. bardus, Aprostocetus nitens and A. tritus, in association with erythrina galls. Two more parasitoids, viz., Eurytoma erythrinae Gates & Delvare (2008) (from South Africa, Tanzania and Ghana) and Aprostocetus exertus La Salle (2009) (from Tanzania) have been described recently. The potential of these species as biocontrol agents of Q. erythrinae remains to be seen.

References