Dendrocerus
Conostigmus
Dendrocerus
Conostigmus
C. lepus
C. triangularis
Conostigmus
Dendrocerus
D. punctipes
D. penmaricus
C. fasciatipennis
Conostigmus
Dendrocerus
Conostigmus
Dendrocerus
Dendrocerus
Conostigmus
Dendrocerus
C. fasciatipennis
Conostigmus
Dendrocerus
Dendrocerus
D. carpenteri
D. conwentziae
Conostigmus
C. fasciatipennis
Dendrocerus
A Taxonomic Revision of Nearctic Conostigmus (Hymenoptera: Ceraphronoidea: Megaspilidae)
Trietsch, Carolyn
Mikó, István
Ezray, Briana
Deans, Andrew R.
Zootaxa
2020
2020-06-15
4792
1
1
155
62MYC
Dahlbom
1858
[399,550,225,251]
Insecta
Megaspilidae
Conostigmus
Animalia
Hymenoptera
146
147
Arthropoda
genus
Dendrocerusand Conostigmuscan be incredibly difficult to distinguish ( Mikó et al., 2011). There are both Dendrocerus-like Conostigmusspecies (including C. lepusand C. triangularis) and Conostigmus-like Dendrocerusspecies (such as D. punctipesand D. penmaricus). It is unclear to which genus C. fasciatipennisbelongs. Dessart (1972b)kept the species within the genus Conostigmusbased 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 Conostigmusand Dendrocerusand determine the generic placement for C. fasciatipennis. Based on preliminary ultraconserved element (UCE) data, Conostigmusis paraphyletic and Dendrocerusis polyphyletic, with a few Dendrocerusspecies ( D. carpenteriand D. conwentziae) nested within Conostigmusand C. fasciatipennisseparating those species from the rest of Dendrocerus(Blaimer et al., in prep.).
Some commonly-used morphological characters for distinguishing Conostigmusand Dendrocerusmales are the ocellar ratios and the shape of the ocellar triangle ( Dessart, 1995b; Dessart and Cancemi, 1987). Dendrocerusmales 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 Conostigmusmales 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 Conostigmuseven have the posterior ocelli closer to the compound eyes than to each other (POL greater than OOL), including C. lepusand C. triangularis. As of now, there are no known Dendrocerusspecies with Conostigmus-like ocellar ratios, but more revisionary work on Dendrocerusis needed to investigate this before a conclusion can be made. Male antennal characters are also commonly used for distinguishing between Dendrocerusand Conostigmus( Dessart, 1995b; Dessart and Cancemi, 1987). Female antennae are indistinguishable between the two genera, but male antennae of Conostigmusare symmetrical and cylindrical in shape, whereas the male flagellomeres of Dendrocerusare usually asymmetrical and can be serrate or trapezoidal. Some Dendrocerusalso have branched flagellomeres ( D. mexicaligroup), a state which is never found in Conostigmus( Dessart, 1995a, 1995b, 1999, 2001). Of course, there are some exceptions in Dendrocerus. Both the D. penmaricusspecies group and the D. punctipesspecies group have symmetrical, cylindrical male flagellomeres that resemble those of Conostigmus( Dessart, 1983b, 1995a). Members of the D. penmaricusgroup can be differentiated from Conostigmusby the maximum scape width, which is greater than the pedicel length in D. penmaricusspecies group members (maximum scape width less than pedicel length in all Conostigmus) ( Dessart, 1995a). The D. punctipesspecies 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 Conostigmusand Dendrocerusspecimens, 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 Dendrocerusbut never in Conostigmus) and the medioventral conjunctiva of the gono-style–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. dimidiatusand C. erythrothorax) and absent in most Dendrocerus(exceptions include D. carpenteri, D. flavipesand D. rectangularis). Other characters that can be useful but are more subjective include metapleural sulcus shape (usually curved in Dendrocerusand straight in Conostigmus, though it appears curved in some Dendrocerus-like Conostigmussuch as C. lepusand C. triangularis), as well as head shape (usually triangular in Dendrocerusand globulose or circular in Conostigmus).