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

publication ID


publication LSID

persistent identifier

treatment provided by


scientific name



[[ Genus Myrmelachista  HNS  ]]

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  HNS  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  HNS  from Cuba; syntypes of rogeri manni  HNS  from Cuba, and syntypes of rogeri rubriceps  HNS  from Cuba. All appear to be similar to plebecula  HNS  . All are bicolored or various shades of red brown. Unlike plebecula  HNS  , all have long erect setae projecting from the sides of the head (workers and queens). Eight queens of ramulorum  HNS  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  HNS  . Unlike ramulorum  HNS  , the longiceps-like queen lacks erect setae on the sides of the head. The smallest ramulorum  HNS  queens and the queens of rogeri  HNS  are in the same size range as plebecula  HNS  queens, but with relatively narrow heads. All measured queens of plebecula  HNS  have CI 85 or greater. The highest CI among the ramulorum  HNS  and rogeri  HNS  queens is 82. Myrmelachista kraatzii  HNS  , ambigua  HNS  , rogeri  HNS  , and ramulorum  HNS  are all older names than plebecula  HNS  , and if plebecula  HNS  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  HNS  and ramulorum  HNS  are distinct. When two Cuban rogeri  HNS  queens I have measured are compared to eight ramulorum  HNS  queens from other islands, they are at the small end of a continuum of measurements.

Myrmelachista ambigua  HNS  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  HNS  from St. Vincent will be needed to compare with material from other parts of the Caribbean. Wheeler (1908) considered the worker of ramulorum  HNS  close to ambigua  HNS  .

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

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

One collection from El Yunque, Puerto Rico, is indistinguishable firom M. longiceps  HNS  . It is a collection of workers and alate queens, collected by Juan Torres. I am reluctant to identify it as longiceps  HNS  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  HNS  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.