Key to the World species of the genus Aivalykus

1. Second metasomal tergite of female entirely smooth; antenna with 14–21 antennomeres. [Brachial (subdiscal) cell closed distinctly before recurrent vein (m-cu)]...................................................................... 2

- Second metasomal tergite of female striate at least on basal one-third or medially, sometimes entirely; antenna with 25–35 antennomeres........................................................................................ 7

2. Vertex entirely smooth................................................................................. 3

- Vertex distinctly transversely striate or micro-aciculate....................................................... 4

3. Mesoscutum completely smooth; first metasomal tergite smooth laterally, distinctly striate medially; antenna with more than 20 antennomeres; head and mesosoma dark reddish brown, metasoma light reddish brown. Body larger, its length 3.3 mm. [Fiji]................................................................. A. levis Belokobylskij, Iqbal et Austin, 2004

- Mesoscutum finely coriaceous; first metasomal tergite entirely and weakly striate; antenna with 16 antennomeres; body entirely honey yellow. Body smaller, its length 1.0– 1.5 mm. [Brazil]................................. A. flavus (Marsh, 1993)

4. Vertex micro-aciculate................................................................................. 5

- Vertex distinctly transverse striate........................................................................ 6

5. First tergite short, its length 0.80–0.85 × its apical width; prescutellar depression (scutal sulcus) with three longitudinal carinae. Body length 1.5–2.0 mm. [India, UAE]............................................... A. microaciculatus sp. nov.

- First tergite long, its length 1.0–1.2 × its apical width; prescutellar depression (scutal sulcus) with single median longitudinal carina. Body length 2.0– 3.8 mm. [China, Indonesia (Java)]...................... A. nitidus Belokobylskij et Chen, 2002

6. Malar space about 0.5 × eye height; mesoscutal lobes shallowly punctuate; basolateral areas of propodeum weakly punctuate; nervulus (cu-a) interstitial. Body length 1.5–2.5 mm. [USA]............................... A. nearcticus Marsh, 1965

- Malar space about 0.35× eye height; mesoscutal lobes coriaceous; basolateral areas of propodeum coriaceous; nervulus (cu-a) distinctly postfurcal. Body length 2.5 mm. [Costa Rica]..................................... A. hansoni Marsh, 2002

7. Recurrent vein (m-cu) postfurcal or rarely interstitial to first radiomedial vein (2-SR); first metasomal tergite twice longer than its apical width; third metasomal tergite at least in basal half longitudinally striate. Female longer, body length 4.5–7.0 mm. [India, Philippines].................................................................. A. eclectes Nixon, 1938

- Recurrent vein (m-cu) more or less distinctly antefurcal to first radiomedial vein (2-SR); first metasomal tergite 1.0–1.4 × longer than its apical width; third metasomal tergite always smooth. Female shorter, body length 3.0–4.0 mm............... 8

8. Brachial (subdiscal) cell closed apically (almost) on level of recurrent vein (m-cu).................................. 9

- Brachial (subdiscal) cell closed apically distinctly before level of recurrent vein (m-cu)............................. 10

9. Antennae with 25–26 antennomeres; sternauli completely absent; second metasomal tergite striate only basally, sometimes striation almost absent. Body length 4.0– 4.5 mm. [India]................................... A. sperches Nixon, 1938

- Antennae with 29–30 antennomeres; sternauli present, but shallow; second metasomal tergite costate only medially. Body length 3.0–4.0 mm. [Costa Rica]...................................................... A. austrinus Marsh, 2002

10. Transverse diameter of eye about twice length of temple; first flagellar segment 0.8 × as long as second segment; radial vein (r) arising almost from middle of pterostigma; brachial (subdiscal) cell apically closed distinctly before recurrent vein (m-cu); length of first metasomal tergite almost equal to or slightly larger than its apical width; hind tibia with dense dorsal setae. Body length 2.8–3.8 (female) and 6.0–7.0 (male) mm. [Ghana].............................. A. endroedyyoungai Papp, 1993

- Transverse diameter of eye 1.6 × length of temple; first flagellar segment 0.6 × as long as second segment; radial vein (r) arising behind middle of pterostigma; brachial (subdiscal) cell apically closed weakly before recurrent vein (m-cu); length of first metasomal tergite 1.5 × its apical width; hind tibia with sparse dorsal setae. Body length 3.0 mm (female). [China]............................................................................. A. bouceki Belokobylskij et Chen, 2002