Conostigmus, Dahlbom, 1858

Trietsch, Carolyn, Mikó, István, Ezray, Briana & Deans, Andrew R., 2020, A Taxonomic Revision of Nearctic Conostigmus (Hymenoptera: Ceraphronoidea: Megaspilidae), Zootaxa 4792 (1), pp. 1-155: 147

publication ID

https://doi.org/10.11646/zootaxa.4792.1.1

publication LSID

lsid:zoobank.org:pub:326F6A15-216E-439A-AD59-3CDF7551D3F6

persistent identifier

http://treatment.plazi.org/id/039687D1-FF10-659D-9FA4-FF0D476FC4EF

treatment provided by

Plazi

scientific name

Conostigmus
status

 

Distinguishing Male Conostigmus   and Dendrocerus   ( Table 3)

Dendrocerus   and Conostigmus   can be incredibly difficult to distinguish ( Mikó et al., 2011). There are both Dendrocerus   -like Conostigmus   species (including C. lepus   and C. triangularis   ) and Conostigmus   -like Dendrocerus   species (such as D. punctipes   and D. penmaricus   ). It is unclear to which genus C. fasciatipennis   belongs. Dessart (1972b) kept the species within the genus Conostigmus   based on the presence of the medioventral conjunctiva (medioventral conjunctiva always absent and parossiculi fused with the gonostipes in Dendrocerus   ). Dessart (1972b) also noted its cylindrical male flagellomeres, which were typical of Conostigmus   .

However, this species also lacks a facial pit (absent in most Dendrocerus   ) and has a Dendrocerus   -like obtuse ocellar triangle in males (POL greater than LOL), where the two posterior ocelli are closer to the compound eyes than to each other (POL greater than OOL). Molecular data has so far been unable to delimit Conostigmus   and Dendrocerus   and determine the generic placement for C. fasciatipennis   . Based on preliminary ultraconserved element (UCE) data, Conostigmus   is paraphyletic and Dendrocerus   is polyphyletic, with a few Dendrocerus   species ( D. carpenteri   and D. conwentziae   ) nested within Conostigmus   and C. fasciatipennis   separating those species from the rest of Dendrocerus   (Blaimer et al., in prep.).

Some commonly-used morphological characters for distinguishing Conostigmus   and Dendrocerus   males are the ocellar ratios and the shape of the ocellar triangle ( Dessart, 1995b; Dessart and Cancemi, 1987). Dendrocerus   males are usually distinguished as having an obtuse ocellar triangle (POL greater than LOL) where the two posterior ocelli are closer to the compound eyes than to each other (POL greater than OOL), whereas Conostigmus   males are usually thought to have an acute or equilateral ocellar triangle (POL equal to or less than LOL) where the posterior ocelli are closer to each other than to the compound eyes (POL less than OOL).

However, this does not hold true for all Conostigmus   . Some species have more obtuse ocellar triangles (POL greater than LOL) in the males, including C. nigrorufus   , C. duncani   , and C. bipunctatus   . Some male Conostigmus   even have the posterior ocelli closer to the compound eyes than to each other (POL greater than OOL), including C. lepus   and C. triangularis   . As of now, there are no known Dendrocerus   species with Conostigmus   -like ocellar ratios, but more revisionary work on Dendrocerus   is needed to investigate this before a conclusion can be made.

Male antennal characters are also commonly used for distinguishing between Dendrocerus   and Conostigmus   ( Dessart, 1995b; Dessart and Cancemi, 1987). Female antennae are indistinguishable between the two genera, but male antennae of Conostigmus   are symmetrical and cylindrical in shape, whereas the male flagellomeres of Dendrocerus   are usually asymmetrical and can be serrate or trapezoidal. Some Dendrocerus   also have branched flagellomeres ( D. mexicali   group), a state which is never found in Conostigmus   ( Dessart, 1995a, 1995b, 1999, 2001).

Of course, there are some exceptions in Dendrocerus   . Both the D. penmaricus   species group and the D. punctipes   species group have symmetrical, cylindrical male flagellomeres that resemble those of Conostigmus   ( Dessart, 1983b, 1995a). Members of the D. penmaricus   group can be differentiated from Conostigmus   by the maximum scape width, which is greater than the pedicel length in D. penmaricus   species group members (maximum scape width less than pedicel length in all Conostigmus   ) ( Dessart, 1995a). The D. punctipes   species group is more difficult to distinguish from Conostigmus   , but can be differentiated by the combination of the fused parossiculi, absence of the facial pit, and Dendrocerus   -like ocellar triangle ( Dessart, 1983b).

Though the characters discussed above can be useful for distinguishing male Conostigmus   and Dendrocerus   specimens, they should not be used individually to make an identification. We recommend using a combination of characters to distinguish genera due to the numerous exceptions and overlap between these two genera. In addition to the characters above, some useful characters include the presence of the sternaulus (always absent in Dendrocerus   , but present or absent in Conostigmus   ), wing presence (wings never absent in Dendrocerus   , but present or absent in Conostigmus   ), notauli posterior end (always adjacent to the transscutal articulation in Conostigmus   , but not adjacent in some Dendrocerus   ) and male genitalia characters including the presence of the parossiculi (parossiculi fused with the gonostipes in Dendrocerus   but never in Conostigmus   ) and the medioventral conjunctiva of the gonostyle–volsella complex (parossiculi never independent in Dendrocerus   , but independent or fused in Conostigmus   ). ( Dessart, 1985, 1995a, 1995b, 1999, 2001; Mikó et al., 2011, 2013). The facial pit is present in most Conostigmus   (exceptions include C. dimidiatus   and C. erythrothorax   ) and absent in most Dendrocerus   (exceptions include D. carpenteri   , D. flavipes   and D. rectangularis   ). Other characters that can be useful but are more subjective include metapleural sulcus shape (usually curved in Dendrocerus   and straight in Conostigmus   , though it appears curved in some Dendrocerus   -like Conostigmus   such as C. lepus   and C. triangularis   ), as well as head shape (usually triangular in Dendrocerus   and globulose or circular in Conostigmus   ).

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Hymenoptera

Family

Megaspilidae

Loc

Conostigmus

Trietsch, Carolyn, Mikó, István, Ezray, Briana & Deans, Andrew R. 2020
2020
Loc

C. lepus

Trietsch 2020
2020
Loc

D. conwentziae

Gahan 1919
1919
Loc

C. fasciatipennis

Kieffer 1907
1907
Loc

C. fasciatipennis

Kieffer 1907
1907
Loc

C. fasciatipennis

Kieffer 1907
1907
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Conostigmus

Dahlbom 1858
1858
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852
Loc

Dendrocerus

Ratzeburg 1852
1852