Microstigmus rosae, Field, 2023

Field, Jeremy, 2023, Description and nesting biology of three new species of neotropical silk wasp (Hymenoptera: Apoidea: Pemphredoninae: Microstigmus), Journal of Natural History 57, pp. 1-18 : 4-9

publication ID	https://doi.org/ 10.1080/00222933.2022.2157345
publication LSID	lsid:zoobank.org:pub:E46768B9-FD13-4370-8E31-8D1819B724F4
DOI	https://doi.org/10.5281/zenodo.7620264
persistent identifier	https://treatment.plazi.org/id/03815C6C-7434-FFD4-E8EC-FE3CFB6DFA73
treatment provided by	Plazi
scientific name	Microstigmus rosae
status	sp. nov.

Treatment

Microstigmus rosae sp. nov.

Recognition

Unlike M. lydiae sp. nov. and M. mirandae sp. nov., this species has the female 3rd antennal segment (i.e. the first flagellomere) almost square ( Figure 3 View Figure 3 (a)), and runs to M. pallidus in Richards (1972). However, the overall colouration is darker than M. pallidus , with the head, including clypeus, mainly black ( Figure 1 View Figure 1 (c)); the 3rd antennal segment is slightly squarer than in M. pallidus ; the sculpturing is coarser, e.g. on the mesopleurae; and the striations at the back of the scutum are longer and denser ( Figure 2 View Figure 2 (a)). In addition, the centre of the posterior margin of tergite 7 in male M. rosae sp. nov. bears a pair of adjacent, upturned and incurved teeth.

Description

Female. Length 3.5 mm. Colouration: head black except sides of lower face dark orange or pale orange, these lateral orange areas not fully meeting centrally ( Figure 1 View Figure 1 (c)). A narrow line adjacent to the inside of the eyes and a strip running around the back of the head, connecting the back of the eyes to the occipital carina, also orange. Clypeus black with orange lower margin. Mandibles dark yellow or pale yellow, similar in colour to antennal scape, with dark red-edged tips. Antennae blackish brown, somewhat paler/yellowish ventrally, darker towards the tips. Pronotum orange with anterior dark mark centrally, and black areas on underside of pronotum in most specimens. Scutum varying in colour from bright orange to a dirty orange-brown. Scutum coloured homogeneously in most specimens, but a few have a hint of the pattern seen in M. lydiae sp. nov. ( Figure 1 View Figure 1 (b)), with a central paler strip running antero-posteriorly and slightly darker areas laterally. Scutellum and metanotum orange laterally with central black area. Mesopleurae partly brown or black, with a small orange area postero-centrally. Underside of mesothorax black. Propodeum and abdomen black/dark brown, with a small dark orange area on each side at the base of the second tergite in some specimens. Variable pale marks on sternites in some specimens, sometimes including a whiteish mark at the base of the 6th sternite. Legs pale yelloworange except: coxae and trochanters more yellowy-white; hind femora dark brown or black dorsally; and hind tibiae more or less brown-marked.

Maximum width of face across the eyes approximately 1.1 times the distance from top of the head to apex of clypeus when head is viewed face-on. Inner margins of compound eyes approximately parallel on face; minimum interorbital distance (across middle of face) approximately 1.1 times interorbital distance near top of the eyes. Ocelli in a not quite equilateral triangle, with the posterior side shorter and the two posterior ocelli separated by a distance approximately equal to their diameters. Mandibles with upper tooth shorter than lower tooth. Malar space short, approximately equal to the width of antennal segment 3. Clypeus raised, anterior margin weakly convex with a more or less weak central tooth often present. Basal flagellar segments of antennae short and relatively square: fifth antennal segment 1.25 times longer than wide; 3rd segment 1.4 times longer than wide and viewed from above, third segment clearly shorter than pedicel ( Figure 3 View Figure 3 (a)). Integument predominantly shining. Frons finely reticulate with fairly dense, shallow punctures. Scutum impunctate, finely reticulate, with striations along the posterior margin visible at 60 × ( Figure 2 View Figure 2 (a)), these striations longer (length 20% of length of scutum) and denser than in M. lydiae sp. nov. and M. mirandae sp. nov. Pronotum with a transverse carina centrally. Scutellum weakly convex when viewed laterally, and moderately raised centrally. Posterior half of the raised area with a raised longitudinal keel centrally with weaker carinae each side. Metanotum with a sharp, raised longitudinal keel centrally. Mesopleurae mostly coarsely sculptured, especially ventrally, but smooth posterodorsally. Omaular sulcus and hypersternaulus well developed, the former unusually wide, wider than in M. lydiae sp. nov. and M. mirandae sp. nov. Propodeum shining and very coarsely sculptured, more so than in M. lydiae sp. nov. and M. mirandae sp. nov.

Pilosity: compound eye bare, top of head and dorsal mesosoma with dense, short setae. In perfect specimens there are two longer, erect setae in the ocellar area that are slightly longer than the distance between the outer edges of the two posterior ocelli. Clypeus and lower edge of mandibles with longer setae. Antennae covered with dense, short setae, especially towards the tips; setae so dense that junctions between basal antennal segments hard to discern in some specimens. Dorsal area of propodeum bare, but posterior face moderately setose, setae longer than on head and mesosoma. Mesopleurae with short, dense setae especially towards the venter and beneath. First two abdominal tergites almost bare, with short setae becoming denser towards the tip of the abdomen, including a few longer setae at the posterior edges of tergites and sternites.

Male. Similar to female except somewhat paler colouration: entire underside of head and pronotum, and the posterior half of tergite 7, pale; and orange area on posterior mesopleurae more extensive than in female, running from wing base to nearly the underside of the mesosoma. Malar space noticeably longer than in the female, approximately 1.5 times the length of the antennal pedicel. Lower face of male is snowy white, starting half-way down the eyes and including the clypeus, and anterior (ventral) side of scape and mandibles pale yellow, contrasting with the white lower face. Male posterior tergites bear central depressions. When the abdomen is in its natural position (segments telescoped), these appear as small, groovelike depressions in the centres of tergites 3–7, the overall impression being of a central flattening of the entire posterior dorsal abdomen, with the black posterior tergal margins appearing emarginate. When the abdominal segments are pulled out, it can be seen that these depressions cover only the apices of tergites 3–5, where they are semi-circular; but cover the entire lengths of the centres of tergites 6–7, where they are oval-shaped. The surface of tergite 2 is smooth, without depressions or grooves. Tergite 7 bears a pair of adjacent, upturned and incurved teeth at the centre of its posterior margin. Sternite 7 narrows towards its bluntly rounded, upturned tip.

Type material

Holotype female. ′ ECUADOR: Pichincha Province: Santa Lucia nr Nanegal (1900 m). Cabana N 0.11843 W 78.61186. 27/ 8-3/9/2014 J.P.Field ̍ with ′12̍ additionally pencilled onto the label (NHM). GoogleMaps

A further 4 female and 2 male paratypes also deposited at NHM, including 2 females and 2 males with the same data as the holotype except with pencil numbers 9, 10 and 13 (females, the latter specimen has the head micro-pinned separately onto the same piece of plastozoate as the body) or ′12̍ (one of the two males) GoogleMaps . The second male, also from Santa Lucia, has similar data to the holotype but: ′(1600 m). N 0.11843 Under W 78.61186 a sign. 3/9/2014 J.P.Field̍ with ′25̍ additionally pencilled onto the label. The final female paratype is from the Mashpi site and has the abdomen missing, with data: ′ ECUADOR: Pichincha, Mashpi Reserve nr Pacto (1050 m) . N 00°09.771 ̍ W 078°52.271, 18–24/9/2014 R GoogleMaps . Bonifacii̍ with ′104̍ additionally pencilled onto the label.

Of two additional female paratypes, both with the abdomen missing, one has data: ′ ECUADOR: Pichincha, Mashpi Reserve nr Pacto (1050 m) . N 00°09.771 ̍ W 078°52.271, 6–7/ 9/2014 J.Field, 34̍. The second female has the same data except that the date, collector and pencil label are: 18–24/9/2014 R .Bonifacii, 101. These last two paratypes are currently in the author̍s collection but the intention is to deposit them at NIBEQ once a visit to Ecuador is possible, post-Covid pandemic. An additional 2 female and 2 male paratypes from the Mashpi site have already been deposited at NIBEQ, and these have similar data to the Mashpi paratypes above except dates in September 2017 .

Etymology. This species is named after Rosa Bonifacii in recognition of her excellent PhD work focussing on its biology.

Biology. Hundreds of nests of this species were located at the two principal study sites, particularly at Mashpi. Nests ( Figure 4 View Figure 4 (a)) were found throughout the 750–2000 masl altitudinal range investigated, and were commoner than nests of the other two species. Nests were found hanging under the leaves of a variety of plants, less often from manmade structures. At Mashpi, they were particularly common beneath the large leaves of Xanthosoma sagittifolium (Araceae) , with more than one nest commonly found on the same plant and sometimes hanging under the same leaf of X. sagittifolium . Each nest was suspended by a thin, normally straight, petiole. Nests were typically brown in colour with a rough external appearance, apparently constructed from tiny pieces of plant material (often with the appearance of wood fragments) interwoven with strands of silk with occasional fragments of arthropod exoskeleton embedded. The nest entrance is located at the apex, where the petiole meets the main nest structure, and the lower part is divided into between 1 and 9 vertically orientated cells, visible externally as bumps on the surface of the nest. The nest entrance diameter was 1.5–2 mm and the nest petiole was usually straight but occasionally slightly or strongly curved, shorter (5–10 mm, mean 7.25) than in M. mirandae sp. nov. Each nest cell contained a single offspring or was empty. Approximately 80% of nests contained just a single adult female, but there could be up to four females and three males. Each offspring was mass provisioned with between 30 and 80 nymphal thrips (Thysanoptera). Cells sometimes contained pupae of braconid wasps ( Heterospilus: Marsh and Melo 1999 ) or chalcidid wasps, and parasite larvae were observed feeding externally on Microstigmus larvae and prepupae.

The following two new species, Microstigmus lydiae sp. nov. and M. mirandae sp. nov., run to M. bicolor (couplet 7) in Richards (1972). Based on the material examined and Richards (1971, 1972) descriptions of M. eberhardi and M. soror , they can be separated from other described species that run to couplet 7 as follows.

1. Scutum black. Prey on thrips............................................................ M. eberhardi View in CoL and M. soror View in CoL

- Scutum entirely orange or with large orange areas both anteriorly and posteriorly ( Figure 1 View Figure 1 ). Prey on Homoptera ( Cicadellidae View in CoL ) (prey of M. bicolor View in CoL unknown)......... 2

2. Head (and mesosoma plus the dorsal surface of the petiole in M. nigrophthalmus View in CoL ) entirely orange, except the male lower face is white, and sometimes the tiny area between the ocelli is black. Larger species (female length 4.5–5.2 mm) with more spherical nests where cells are not visible from the outside.................................................... ....................................................................................................... M. bicolor View in CoL and M. nigrophthalmus View in CoL

- Dark patches on the head ( Figure 1 View Figure 1 ) as well as the mesosoma, least so in pale specimens of M. mirandae sp. nov. ( Figure 1 View Figure 1 (a)). Dorsal surface of petiole black/ brown or with black/brown marks. Smaller species (female length 4 mm) with less spherical nests that have cells visible as bumps on the outside ( Figure 4 View Figure 4 ).................. 3

3. Colouration of female head and mesosoma darker, with a thick black line along top edge of clypeus ( Figure 1 View Figure 1 (d)). Mesopleurae lacking striations latero-ventrally. Short striations present at the back of the scutum at high power ( Figure 2 View Figure 2 (b)). Anterior face of male antennal scape pale yellow, contrasting with white lower face and mandibles. Surface of male second tergite smooth, without depressions or grooves.................................................... .................................................... M. lydiae sp. nov.

- Colouration of female head and mesosoma paler, with the clypeus entirely pale, lacking a thick black line along its top edge ( Figure 1 View Figure 1 (e)). Mesopleurae with clear striations latero-ventrally ( Figure 2 View Figure 2 (d)). Striations absent or very weak at the back of the scutum, even at high power ( Figure 2 View Figure 2 (c)). Anterior face of male antennal scape white (except yellowish distally at the junction with segment 2), concolorous with lower face and mandibles. Male second tergite with a central, narrow, groove-like depression running along the posterior three-quarters or more of the segment.......... ............................................................................................................................... M. mirandae sp. nov.