Hypogastrura gami ( Wray, 1952 ) Wray, 1952

Bernard, Ernest C., 2015, Redescriptions of Hypogastruridae and Onychiuridae (Collembola) described by David L. Wray, Zootaxa 3918 (3), pp. 301-338 : 309-310

Hypogastrura gami ( Wray, 1952) , new synonym of Hypogastrura humi ( Folsom, 1916)

Fig. 5

Achorutes gami Wray 1952: 98 .

Hypogastrura gami Salmon 1964: 214 ; Christiansen & Bellinger 1980: 116.

Specimens of A. gami examined. Fifteen juveniles, USA, Illinois, Magnolia, 23–24 May 1944, ground cover, H. H. Ross, coll.

Redescription. Body length 0.58–0.61 mm [up to 0.75 mm]. [Color light blue splotched and specked over a yellow background.] Head without setae a0,c2 and sd5. Pronotum without setae ( Fig. 5 A). Thoracic and abdominal sensilliform setae at least twice as long as the longest body setae.( Figs. 5 A, B). Setae p3 and p4 behind other psetae on mesonotum and metanotum. Seta m2 absent. M-row setae and seta p2 absent on abdominal terga I–IV except m1 and p2 present on Abd. IV.

Antennal segment IV with simple apical bulb, with one dorsal and two lateral sensilla, minute rod-like organite, and distinct microsensillum behind lateral sensilla ( Fig. 5 D); all dorsal setae sensilliform except two short typical setae mid-dorsally and apically. Small sensilla of Ant. III sense organ straight, rod-like with rounded apex, flanked by longer straight sensilla; microsensillum present ( Fig. 5 D). Postantennal organ with four lobes, slightly wider than neighboring ocelli; posterior lobes slightly larger than anterior lobes ( Fig. 5 C). Tibiotarsi I, II, III with 19, 19, 18 setae, respectively; fore and middle tibiotarsi with three clavate tenent hairs (A1, A2, B2) ( Fig. 5 E), tibiotarsus III with four clavate tenent hairs (A1, A2, A7, B2) ( Fig. 9 F); unguis with ventral tooth, without lateral teeth; unguiculus with rounded basal lamella and short apical filament. Dens three times the length of the mucro, with five smooth setae; mucro linear, rounded at tip, with shorter rounded lamella ( Fig. 5 G).

Remarks. All of the type specimens are small juveniles. Specimen lengths are very similar and guts are without contents. The pronotum lacks setae, a character apparently not previously noted for early-instar hypogastrurids. In previous studies, hypogastrurid first instars have been described as having 1+1 setae on the pronotal disc ( Thibaud 1967, 1969, 1970, Weiner 1989). Length of these H. gami juveniles is greater than that reported by Weiner (1989) for the first and second instars (prelarvae, stages I and II) of Ceratophysella monstruosa (Gisin) (= C. mosquensis (Becker, 1905)) , but close to that of the “larva I” (third instar). In C. bengtssoni ( Ågren, 1904) instars I, II, III have 0, 3, 6 sensilla on Ant. IV, respectively ( Thibaud 1967, 1970). The H. gami juvenile Ant. IV ( Fig. 5 D) corresponds to the second instar of C. bengtssoni , but all instars of that species have at least 1+1 setae on the pronotum ( Thibaud 1967, 1970). The lack of pronotal setae in these early-instar specimens may represent a significant dichotomy in hypogastrurid developmental patterns.

Hypogastrura gami is considered here to be a junior synonym of H. humi ( Folsom, 1916) . In Christiansen & Bellinger (1980, 1998) these specimens will key to the two-couplet group of H. humi / H. gami / H. perplexa Christiansen & Bellinger, 1980 . Both H. humi and H. gami have an apically truncated or rounded mucronal lamella, whereas that of H. perplexa tapers apically. Both H. humi and H. perplexa have North American transcontinental distributions according to Christiansen & Bellinger (1980, 1998), but those authors have suggested that collections of H. humi and H. perplexa may represent a number of species. Specimens of H. gami reported from other North American localities need to be reevaluated since the species is based on an early instar.

Figures

FIGURE 5. Hypogastrura gami (= H. humi). A) Chaetotaxy of head and thorax, dorsal view. B) Chaetotaxy of abdomen, dorsal view. C) Postantennal organ and anterior ocelli. D) Third and fourth antennal segments, dorsal view. E) Fore-tibiotarsus. F) Hind tibiotarsus. G) Dens and mucro, lateral view.

FIGURE 9. Hypogastrura ireneae. A) Postantennal organs (PAO) on paralectotypes. B) PAO and anterior eyes, paralectotype. C) PAO and anterior eyes, lectotype. D) Third and fourth antennal segments, dorsal view. E) Fourth antennal segment, ventral view. F) Sense organ of third antennal segment. G) Labial palpus. H) Head of maxilla, lectotype, and views of lamellae from other specimens. I) Hind foot, lateral view, lectotype. J) Middle unguis, dorsal view, lectotype. K) Middle unguis, dorsal view, paralectotype. L) Left dens and mucro, lectotype. M) Right mucro, lectotype.