The genus should be placed more correctly under Hemiacridinae, rather than Catantopinae. In Willemsella, the basal and apical penis valves are separated, diagnostic for species in Hemiacridinae. In Catantopinae, the basal and penis valves are connected. The genus also exhibits a series of regular transverse veinlets near the radial area of tegmen, similar to those found in Hemiacridinae and usually absent in Catantopinae. Willemsella also shares characters of Catantopinae: presence of prosternal spine, rounded mesosternal lobes and absence of intercalary veins in the medial area of tegmen.

Adult habitus as shown in Fig. 1. Head about as long as pronotum (Fig. 2a, b, d, e). Frontal ridge narrow, parallel-sided dorsal and ventral of median ocellus; ridge more deep but narrower in males than females (Fig. 2c, f). Fastigium of vertex broadly rounded to subtruncated (Fig. 2b, e). Vertex between eyes average about 4.3 times in males (n=3, min=3.5, max=5.0) and 2.0 times (n=2, min=2.0, max=2.0) in females as broad as frontal ridge between antennae. Eyes large. Antennae about 20-segmented, flattened; reaching and surpassing posterior margin of pronotum in males, and reaching middle but not surpassing posterior margin of pronotum in females. Pronotum long, crossed by three transverse furrows (Fig. 2b, e); prozona 1.7 times in male (n=3, min=1.5, max=2.1) and 2.1 times in female (n=2, min=1.9, max=2.4) as long as metazona; anterior margin of prozona truncated to feebly convex; posterior margin of metazona broadly rounded; lateral carinae absent; median carina indistinct, more distinct along metazona. Prosternal spine distinct, flattened and triangular basally, narrowing into a long and subacute apex. Mesosternal lophi with internal margin broadly rounded; mesosternal interspace slightly less broad than lobe. Metasternal lophi with internal margin broadly rounded, separated feebly by metasternal interspace. Tegmen truncated with rounded apex, overlapping each other in rest position, elongated and reaching base of epiproct in males and base of 8^th tergite in females. Radial area of tegmen with a series of regular transverse veinlets (Fig. 2a, d). Hind wings concealed under tegmen. Hind femora 4.7 times (n=5, min=4.6, max=4.8) as long as maximal width of these femora; dorsal carina smooth; knee with dorsal external lobe subtruncated to angular. Hind femora 1.1 times (n=5, min=1.1, max=1.1) longer than hind tibiae. Hind tibiae setose, with 8 outer dorsal subapical spines and 8 inner dorsal subapical spines; with 2 outer and 2 inner apical dorsal spines. Hind tarsi about a third of hind tibiae; third segment (without claws) longer than the two basal segments together; arolium large, almost reaching apex of claws.

a

b

c

d

Figure 1.

In-situ images of Willemsella bicolor Miller, 1934 from Peninsular Malaysia (Tan and Kamaruddin 2014).

a: Male adult.  
b: Male adult.  
c: Male adult.  
d: Female adult.  

a

b

c

d

e

f

Figure 2.

Willemsella bicolor Miller, 1934. Scale bars: 1 mm.

a: Male head and pronotum in lateral view.  
b: Male head and pronotum in dorsal view.  
c: Male face in anterior view.  
d: female head and pronotum in lateral view.  
e: Female head and pronotum in dorsal view.  
f: Female face in anterior view.  

Male. Epiproct broadly tongue-shaped with an apical lobe; median sulcus shallow, broad and feeble, only in the basal half bordered by broad parallel carinae; apical lobe triangular with obtuse apex (Fig. 3a). Cercus in dorsal view compressed and gently curved externally; apex obtusely rounded. Subgenital plate conical, with obtuse apex (Fig. 3a). Male phallic complex as in Fig. 3b, c. Epiphallus bridge (B), very broad and stout, slightly curved along apical margin. Anchora (A) articulated, extending in less than 90º-angle to epiphallus bridge, apex obtuse from dorsal view; membrane between lophi sparsely granulated. Anterior projection (An) of epiphallus swollen and somewhat sparsely granular, forming at less than 90º-angle to the anchora. Lophi (L) stout and transverse, forming highly sclerotized lateral angles; internal angle bulbous and granular, external angle slightly flattened and obtuse, less sclerotized and granular. Ectophallic membrane thickened to form a dorsal and paired ventral ectophallic sclerites; dorsal ectophallic sclerite (Dsv) more membraneous, bridge-shaped with paired cranial appendages covering the cingulum dorsally and laterally; ventral appendages ventral ectophallic sclerites (Esv) rounded, sclerotized and granular. Apodemes (Apd) robust, weakly sclerotized, extending to basal end. Arch of cingulum (Ac) sclerotized, more so internally; finely granulated externally. Basal and apical penis valves separated (Fig. 3c​). Basal valves of penis (Bp) broadening basally, more sclerotized internally; apical valves (Ap) truncated and sclerotized, slightly surpassing arch of cingulum.

a

b

c

d

e

f

Figure 3.

Willemsella bicolor Miller, 1934. Scale bars: 1 mm.

a: Male abdominal apex in dorsal view.  
b: Male phallic complex in dorsal view.  
c: Basal and apical penis valves in dorsal view.  
d: Female abdominal apex in dorsal view.  
e: Female abdominal apex in lateral view.  
f: Female abdominal apex in ventral view.  

Female. Tenth abdominal tergite with posterior margin rounded-triangularly excised, without lateral lobe (Fig. 3d). Supra–anal plate elongated, separated into two parts by a middle transverse carina, apical half broadly tongue-shaped with obtuse apex (Fig. 3d). Transverse carina of supra-anal plate continuing laterally. Cercus triangular with pointed apex. Subgenital plate rectangular slightly longer than broad; posterior margin with large median angular projection and without lateral excisions (Fig. 3f). Ovipositor with long setae, short, hook-like; dorsal valves smooth with apex gently curved dorsad; ventral valves with apex bent ventrad (Fig. 3e).

Colouration (Fig. 1). Male generally brightly green, female brown to olive brown. Head in male mostly green with some patches of yellow beneath eyes at gena and frons; in females, brown dorsally and anteriorly with some dark olive green patch, dark olive green laterally. Scapus and pedicel black, sometimes with white ring apically. Antennal segments bright red. Disc of pronotum green in male and brown in female; lateral lobes with dorsal third dark green in male or dark olive brown in female, basally with a bright yellow spot extending from the anterior to the posterior margins of lateral lobe. Tegmen green in male and brown in female. Fore and mid femora and tibiae green, with knees black, tarsi dark in male; brown in female. Hind femur generally green in male and brown in female; dorso-basal area yellow, ventro-internal bright red; hind knee black. Hind tibia dark blue. Abdominal tergite green in male or brown in female with dark and pale yellow spots. Thoracic and abdominal sternites bright red.

Measurement of alcohol-preserved dry-pinned specimens, in mm (mean in bracket). Male (n=3) BL: 18.4-19.9 (19.1), VW: 0.5-0.7 (0.6), FRW: 0.1-0.2 (0.1), PL: 3.4-4.2 (3.8), PZL: 2.3-2.6 (2.4), MZL: 1.1-1.6 (1.4), PW: 3.0-3.4 (3.2), TL: 7.9-8.7 (8.4), HFL: 12.7-13.6 (13.1), HFW: 2.7-2.9 (2.8), HTL: 11.5-12.5 (12.0); female (n=2) BL: 21.9-22.4 (22.2), VW: 1.0, FRW: 0.5, PL: 5.2-5.5 (5.4), PZL: 3.4-3.9 (3.7), MZL: 1.6-1.8 (1.7), PW: 4.1-4.6 (4.4), TL: 9.9-10.2 (10.1), HFL: 15.4-15.9 (15.7), HFW: 3.2-3.4 (3.3), HTL: 14.0-14.2 (14.1).

Prosternal spine distinct, flattened and triangular basally, narrowing into a long and subacute apex. Radial area of tegmen with a series of regular transverse veinlets. Anchora (A) articulated, extending in less than 90º-angle to epiphallus bridge, apex obtuse from dorsal view; membrane between lophi sparsely granulated. Anterior projection (An) of epiphallus swollen and somewhat sparsely granular, forming at less than 90º-angle to the anchora. Basal and apical penis valves separated. Antennal segments bright red. Lateral lobes with a basal bright yellow spot extending from the anterior to the posterior margins of lateral lobe.

Malay Peninsula: Bukit Larut, Perak; Bukit Fraser, Pahang; Dusan Tua, Selangor (Miller 1934).

Little is known about the ecology of this grasshopper species. they are fairly common among tall grasses in Bukit Fraser and Bukit Larut, suggesting that they may prefer high elevations.

So far endemic to Peninsular Malaysia.