Myrmelachista

Longino, J. T., 2006, A taxonomic review of the genus Myrmelachista (Hymenoptera: Formicidae) in Costa Rica., Zootaxa 1141, pp. 1-54 : 49-50

[[ Genus Myrmelachista ]]

The above are all the species and subspecies known from Caribbean islands. My knowledge of the Caribbean fauna is limited, but I have examined 20 collections of ramulorum from Puerto Rico, St. Croix, USA (Florida, possibly introduced and then extirpated, see Deyrup 2003), Santo Domingo, St. Thomas, and the Dominican Republic; three collections of rogeri from Cuba; syntypes of rogeri manni from Cuba, and syntypes of rogeri rubriceps from Cuba. All appear to be similar to plebecula . All are bicolored or various shades of red brown. Unlike plebecula , all have long erect setae projecting from the sides of the head (workers and queens). Eight queens of ramulorum are very small with very narrow, rectangular heads. The largest of these have the narrowest heads, with HW around 0.70mm and CI around 74, a combination not found in any Costa Rican species except for the one small longiceps-like queen described under longiceps . Unlike ramulorum , the longiceps-like queen lacks erect setae on the sides of the head. The smallest ramulorum queens and the queens of rogeri are in the same size range as plebecula queens, but with relatively narrow heads. All measured queens of plebecula have CI 85 or greater. The highest CI among the ramulorum and rogeri queens is 82. Myrmelachista kraatzii , ambigua , rogeri , and ramulorum are all older names than plebecula , and if plebecula proves to be an allopatric variant of a widespread polytypic Caribbean species it will no doubt be a synonym of one of these older names.

It is not clear that rogeri and ramulorum are distinct. When two Cuban rogeri queens I have measured are compared to eight ramulorum queens from other islands, they are at the small end of a continuum of measurements.

Myrmelachista ambigua was described from a single worker from St. Vincent. Given the relative uniformity of workers, the published description and even examination of the type will be of little use. Queen and male-associated collections of Myrmelachista from St. Vincent will be needed to compare with material from other parts of the Caribbean. Wheeler (1908) considered the worker of ramulorum close to ambigua .

Myrmelachista gagates , from Haiti, was described as being close to rogeri but solid black.

It will be important to examine multiple collections of Myrmelachista from Cuba, to ascertain whether there are multiple sympatric species there. It is unknown whether kraatzii and the forms of rogeri are distinct or represent one variable species. Myrmelachista kraatzii from Cuba and M. nigella from Venezuela are the two oldest names in the genus, kraatzii being a 9-segmented form and nigella a 10-segmented form. Thus kraatzii would have priority among all the 9-segmented forms.

One collection from El Yunque, Puerto Rico, is indistinguishable firom M. longiceps . It is a collection of workers and alate queens, collected by Juan Torres. I am reluctant to identify it as longiceps until more Puerto Rican material is obtained, but there is a large size gap between the queen of this El Yunque collection and the various queens of ramulorum from elsewhere in Puerto Rico.

From these observations it is clear that more collections are needed from the Caribbean to better understand species boundaries in this group.