Found inside house, at window, 8/6/24. Collected ... specimen ID 2406A.

Perhaps it came in with sticks we collected for firewood. After taking these few shots, I euthanized & preserved her (dry) for detailed examination.

Less than 5mm long, and with a cuboidal head.

overall head+body length ~ 4.5mm

head rectangular in dorsal view

clypeus very short

eyes widely separated and near parallel

forewing with 2 submarginal cells

gaster sessile
(dorsal view)

gaster sessile
(lateral view)

eyes slightly convergent above; paraocular sulcus not evident along inner margins of eyes

eyes broadly separated, slightly convergent above; paraocular sulcus not evident along inner margins of eyes

- pitted paraocular sulcus (arrows) along outer edge of eye
- palpi short

- obvious frontal carina (solid, green arrows) extending onto clypeus and raised in the interantennal space
- well-developed scapal basin (dashed, pink arrows)
- palpi short

obvious frontal carina (arrows) extending onto clypeus

- frontal carina extends dorsally (arrows) to mid ocellus
- clypeus dark (not 'densely silver')

occipital carina present, and complete ventrally (arrows)

- hindwing media diverging before cu-a
- cu-a angled and appendiculate

(for nomenclature, see Fig. 5, Bohart & Menke 1976)

- forewing stigma large (i.e. 2-3x long as high) & completely covered by setae (i.e. micropore field not differentiated)
- forewing marginal cell also large
- single recurrent vein

SCII of forewing is trapezoidal, not triangular

1. "Second submarginal cell trapezoidal or cubical, or if triangular, not distinctly stalked" –> 2

[excludes: A. queenslandensis]

Head and mesosoma not strongly flattened; pronotum not elongated.

2. "Head globular to elongate, not at all flattened; pronotum transverse, not elongated and mesosoma not markedly compressed dorsoventrally" –> 4

[excludes: A. similus; A. platycephalus]

Head and body entirely black/dark brown, including the clypeus and mesosoma (except the pronotal lobe), not marked with yellow, red-orange or cream. The antennae, mandibles, legs, tegula and pronotal lobe are orange-light brown.

4. "Body entirely black or dark brown, except occasionally tegula and/or pronotal lobe lighter" –> 15

[excludes: A. ruficollis; A. kakaduensis; A. tricolor; A. flavifrons; A. hursti; A. magneticus; A. arator; A. sulcatus; A. deserticolus; A. steindachneri; A. kohlii]

Mandible curved and gradually narrowing toward bidentate apex, not "strongly angulate at base and broadened just before apex".

15. "Mandible ... curved at base and gradually narrowing toward apex" –> 16

[excludes: A. mimi]

Occipital carina ends dorsolaterally (dotted arrows), so is not complete dorsally.

16. "Occipital carina incomplete, evanescent or interrupted dorsally" –> 18

[excludes: A. reticulatus; A. termes]

As this feature is a bit difficult to see, I include this second image from a slightly different angle.

Mesoscutum with fine, punctate sculpture ... perhaps best closely matching Eady's (1968) illustration of 'punctate' microsculpture (Fig. 4. p.66). NOT with distinct, transverse carinulae.

18. "Mesoscutum mostly finely punctate; gena not strongly strigose" –> 19

[excludes: A. transversus]

Genae evenly, finely coriaceous (see Eady 1968, Fig. 8, p. 67), not strongly strigose (see Eady 1968, Fig. 22, p. 67).

18. "Mesoscutum mostly finely punctate; gena not strongly strigose"–> 19

[excludes: A. transversus]

Frontal carina evident between antennae, and does appear slightly translucent along the edge ... however, I doubt this meets the definition of a "translucent lamella".

19. "Frontal carina low, barely raised between antennal scrobes" –> 20

[excludes: A. dubius] *see also comments below

Frontal carina not prominent in the interantennal region.

19. "Frontal carina low, barely raised between antennal scrobes"–> 20

[excludes: A. dubius]

Genal carina definitely present! Also, pronotal carina discrete.

20. "Pronotal carina not especially raised, the anterolateral margin smoothly rounded, not at all projecting (with reference to a dorsal view); genal carina present" –> A. deakinus

[excludes: A. glabrellus; A. approximatus]

Pronotal carina low, not strongly raised, and without an angulate anterolateral margin.

20. "Pronotal carina not especially raised, the anterolateral margin smoothly rounded, not at all projecting (with reference to a dorsal view); genal carina present"–> A. deakinus

[excludes: A. glabrellus; A. approximatus]

"OD = maximum diameter of lateral ocellus = 3;
OOL = minimum distance between lateral ocellus and compound eye = 5;
POL = minimum distance between lateral ocelli = 4;
VOL = longitudinal distance between lateral ocelli and back of head (as seen in vertical view) = 15;
UFW = distance between compound eyes measured at level of anterior ocellus = 19"

The measurements are relative, not in absolute units. If I take the OD of 2406A as 3, then:
OOL = 5.3
POL = 2.3
VOL = 9 (or VOL dotted line = 15)
UFW = 18.5

So in comparison, 2406A has less distance between the lateral ocelli. Depending upon how the authors measured the VOL, 2406A has either the same VOL (dashed dimension) or a significantly shorter VOL (solid line).

"length of body (excluding antennae) = 4.6mm"

I estimate 2406A at around 4.5mm. The curved posture makes a more accurate measurement a bit tricky.

"length of forewing (apex to tegula) = 3.5mm"

Intact, the wing of 2406A would be 3.5mm

Nearly all Pemphredoninae have 2 submarginal cells and an enlarged stigma.

The shape of the submarginal cells varies considerably between species.

A distinct occipital carina is a feature of most crabronids (solid, straight arrows). The extent may vary, sometimes useful in distinguishing species within a genus. In Arpactophilus it is present, at least ventrally.
[Note that in this particular species, there is an additional, strong genal carina – dotted, curved arrows]

Spilomenina is unusual in completely lacking an occipital carina. The rear of the head looks remarkably smooth and rounded (see examples below).

The median ridge (arrows) running to the mid ocellus is typical of Arpactophilus. In Spilomena, it is very short, barely reaching half way to the ocellus.

Deep depressions above the antennal sockets (arrows) are characteristic of several Pemphredoninae, including Arpactophilus. In contrast, there is only the barest indication of such ‘scapal basins’ in Spilomena.

Many Pemphredoninae have a groove alongside the eye (arrows). Often it is along the inner and/or upper margin of the eye, while In others (such as here) the groove completely encircles the eye. It may also be pitted (foveate’), as here.