Micromyzus platycerii Mroz & Depa

Mroz, Ewa, Depa, Lukasz, Artchawakom, Taksin & Gorczyca, Jacek, 2014, Micromyzusplatycerii sp. n. (Hemiptera, Aphididae) - a new fern-feeding aphid species from Thailand, ZooKeys 456, pp. 49-57 : 50-54

Taxon classification Animalia Hemiptera Aphididae

Micromyzus platycerii Mroz & Depa sp. n.

Etymology.

Named after its host plant, from which it was collected: Platycerium coronarium (Konig) Desv.

Diagnosis.

The species belongs to the genus Micromyzus , because its alate female has dark-bordered wing veins and strongly curved radial sector. The new species differs from other representatives of the genus Micromyzus (including Micromyzus katoi sensu Eastop 1966) by:

longer siphunculi: 2.57-3.08 of cauda vs. less than 2.4 in Micromyzus katoi , Micromyzus vandergooti

different ratio of VIa/VIb: apterae 3.87-4.29 (but alatae: 4.54-4.75) vs. 4.4-6.0 in Micromyzus katoi ;

higher ratio of siphunculus length/diameter of siphunculus in the middle: apterae: 8.17-8.98, alatae 7.04-8.86 vs. 5-8 in Micromyzus katoi sensu Eastop, 1966;

lack of dorsal sclerotisation vs. dorsal sclerotic crossbars in Micromyzus diervillae , Micromyzus mawphlangensis ;

pale cauda vs. dark cauda in Micromyzus niger ;

pale tibiae vs. dark tibiae in Micromyzus osmundae , Micromyzus nikkoensis ;

higher number of accessory hairs on ultimate rostral segment than in Micromyzus pojanii ;

lower number of secondary rhinaria on antennal segment III than in Micromyzus hangzhouensis .

The following key may be applied, which is a modification of the last part of the key to apterae on Polypodium and other fern-feeding aphids from Blackman and Eastop (2006). Using their key, Micromyzus platycerii will run to couplet 52, where the siph./cauda ratio is discriminatory:

Descriptions.

Apterous viviparous female (Fig. 1) (measurements based on 6 specimens). Body in life brown, with reddish eyes. Body 2.16-2.68 mm long (incl. cauda), weakly pigmented. Head weakly sclerotised, with sparse and minute spicules on well developed, diverging frontal tubercles (Fig. 2). Antenna 6 segmented, 2.96-3.23 mm long, 1.20-1.26 of body length, covered with short setae, shorter than basal diameter of antennal segment III. Antennal segments I and II dusky, antennal segment III pale, with darker tip and 1- 2 secondary rhinaria on basal part, 0.68-0.81 mm long; antennal segment IV darker towards the end, 0.61-0.72 mm long; antennal segment V dark, 0.42-0.51 mm long; antennal segment VI dark, VIa: 0.17-0.19 mm, VIb: 0.74-0.77 mm, ratio VIa/VIb 3.87-4.29. Rostrum 0.71-0.82 mm long, reaching to the hind coxae, 0.28-0.34 of body length, 0.91-1.16 of the length of antennal segment III. Ultimate rostral segment 0.186-0.192 mm long, 1.81-2.00 of the second segment of hind tarsus, with 8-11 accessory setae.

Prothorax sclerotised, mesothorax with marginal and spinal sclerites, metathorax with marginal sclerites only. Mesothoracic furca not separated, weakly pigmented. Legs covered by short, pointed hairs, shorter than the middle diameter of tibia. Distal half of femora dark; tibiae pale except for dark apices, tarsi black. Ventral side of each first tarsal segment with one thick, pointed, peg-like seta and two thinner setae (Fig. 3). Second segment of tarsus 0.096-0.103 mm long.

Abdomen membranous, with single, very small marginal scleroites, sometimes bearing a small marginal tubercle on abdominal tergite II or III. Small antesiphuncular and bigger postsiphuncular sclerites present. Each tergite with a row of short, pointed setae. Reniform spiracles placed at the posterior end of small scleroits. Siphunculi dark, slightly swollen in the middle, discretely imbricated, with 2-3 rows of distinct imbrications just below the apex (Fig. 4), 0.59-0.69 mm long, 2.57-2.77 of cauda. Subgenital fig broadly elliptical, 0.26-0.31 mm wide, with 2-3 longer setae on its anterior border and a row of shorter setae at its posterior border. Cauda pale, finger-shaped with broader base, 0.22-0.27 mm long, with 4-5 setae (Fig. 4).

Alate viviparous female (Fig. 5) (measurements based on 2 specimens). Body in life brown, 1.95-1.97 mm long (incl. cauda). Head sclerotised, dark and smooth, with low, divergent frontal tubercles, only delicately imbricated; covered sparsely with a few short, pointed setae (Fig. 6). Compound eyes well developed, with triommatidium. Antennae 2.63-2.69 mm long, 1.35-1.36 of body length; antennal segments I–III darker than IV–VI. Length of antennal segments: III 0.56-0.59, IV 0.55-0.56, V 0.42-0.43, VIa 0.15-0.17, VIb 0.73-0.76, ratio of VIb/VIa 4.54-4.75. Antennal segment III with 11-14 secondary rhinaria along its entire length (Fig. 7), segment covered with setae shorter than 0.5 of its basal diameter. Rostrum 0.85-0.90 mm long, 1.43-1.59 of the length of antennal segment III, 0.43-0.46 of body length, reaching past hind coxae. Ultimate rostral segment 0.18-0.19 mm long, 2.00-2.07 of the second segment of hind tarsus, with 8-9 accessory setae.

Thorax heavily sclerotised. Wings with very dark pigmentation of veins and their borders, especially on proximal cubital vein (Fig. 2). Media of fore wing with two forks. Radial sector strongly curved. Legs dusky, with darker apices of femora and tibiae, covered with short pointed setae. Tarsi dusky, first segment with 3 setae, including one sensory peg-like seta; second segment of hind tarsus 0.09 mm long.

Abdomen membranous, with transverse rows of short, pointed setae and with marginal sclerites only. Antesiphuncular and postsiphuncular sclerites well developed. Reniform spiracles placed at the posterior end of small scleroits. Genital fig broadly oval, 0.23-0.26 mm wide, with two setae on the anterior edge and 4-6 setae on the posterior edge. Siphunculi 0.50-0.51 mm long, 2.60-3.08 of the length of cauda, clavate, slightly swollen in the middle, dusky, with 2-3 rows of distinct imbrications at the apex, just below weakly developed flange (Fig. 8). Cauda finger-shaped, pale, 0.17-0.19 mm long, with 4-5 setae.

Biology.

The brown, shiny aphids were feeding on young shoots of Platycerium coronarium , in great numbers on the undersides of leaves.