Identification key to Atta!

Part of our Scientific Interest area. This section is for contributions to Leaf Cutting Ants taxonomy. This may be photographs, descriptions, identification keys, discussion about species level characteristics etc.
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Acromyrmexbob
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Identification key to Atta!

Post by Acromyrmexbob » Fri May 11, 2018 3:33 pm

Sourced at http://www.keyapa.com/leafcutters/keys/borgmeier.htm

Havent worked through this but looks good. A field ID guide would be useful when neck deep in soldiers! Be able to dig one out from my arm and check it against the guide!

Soldiers :

1. Frontal area on both sides with wooly hairs ; head shining or dull ; head width 5;5 - 6;4 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cephalotes ( Linn. )
- Frontal area without wooly hairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. The whole body with light colored , against the body lying pubescence ; as good as without hairs ( except clypeus , frontal carina and underside ) ; head width 4.2 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . colombica Guérin
- Body without light colored , against the body lying pubescence ; thorax always , although sometimes thinly , hairy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3. Stigmata ( tracheal openings ) on both sides of the petiole protruding , visible from above . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
- Stigmata ( tracheal openings ) on the petiole not protruding . . . . . . . . . . . . . . 6

4. Occipital lobes and first gastral segment nude , shiny ; occipital grove shallow , corner between sides more than 90 degrees ; head width 4.6 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . mexicana ( Fr. Smith )
- Occipital lobes and first gastral segment with hairs ; deeper occipital grove , sides meeting less than 90 degrees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

5. Thorns on mesonotum cylindrical , not pointed , shorter than those on the epinotum ; thorns on epinotum curved to the ground ; head width 5 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . insularis Guérin
- Thorns on mesonotum sharp pointed , longer than those on the epinotum ; thorns on epinotum horizontal ; head width 4.1 mm . . . . . . . . texana ( Buckley )

6. Head width 6 - 7.7 mm , length 13 - 16 mm . . . . . . . . . . . . . . . . . . . . . . . . . . 7
- Head width 4.8 - 5.4 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7. Head polished and strongly shiny ; head width reaches 7.7 mm , total length reaches 16 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . laevigata ( Fr. Smith )
- Head not polished , weakly shining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

8. Occipital grove very deep ; head width reaches 6.4 mm . . . bisphaerica Forel
- Occipital grove shallower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

9. Gaster dull , with hairs , clearly wider than ½ head width ( 54:80 ) ; head width 6.2 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . robusta Borgmeier
- Gaster shiny , short pubescence , around ½ head width ( 45:80 ) ; head width reaches 6.2 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . opaciceps Borgmeier

10. Upper part of the head with hairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
- - Upper part of the head nude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

11. Head normally very hairy , dull ; head width 5 mm . . . . . . . sexdens ( Linn. )
- - Head with only a few hairs , almost nude , normally a little bit shiny ; head width 5.3 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . capiguara Gonçalves

12. Occipital lobes without tubercules ; postpetiole rounded , without a sharp ridge or tooth ; head width 5 mm . . . . . . . . . . . . . . . . . . . . . . . . . . saltensis Forel
- - Occipital lobes with tubercules ; postpetiole with a sharp ridge . . . . . . . . . 13

13. First gastral segment polished , practical without hairs ; head width 5.4 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vollenweideri Forel
- - First gastral segment dull , very hairy ; head width 4.8 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . goiana Gonçalves

Males :

A combination of the keys to the subgenera and to the males .

1. Stipes and squamula with an elbowed articulation , not grown together ; ventral middle ridge of the sagitta with teeth ( forming a pair of rows , they are curved and dorsal oriented ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
- Stipes and squamula fixed together , forming one structure ; ventral side of the sagitta in the middle without teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2. Frontal carina with a tooth . Squamulae dorsal , in the middle , not grown together ; sagitta on both sides with a sharp ( vertical ) ridge along its length and alongside it a curved hook or hooks . . . . . . . . . . . . . . . ( subgenus Atta s. str. ) 3
- Frontal carina without a tooth . Squamulae dorsal , in the middle , grown together ; sagitta on the sides without ridge or hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ( subgenus Archeatta Gonçalves ) 4

3. Squamula , seen from above , on both sides longer than broad . Side hooks of the sagitta long . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cephalotes ( Linn. )
- Squamula , seen from above , on both sides as long as broad . Side hooks of the sagitta shorter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . colombica Guérin

4. Dorsal borders on the inside of the squamula straight , not curved outward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . mexicana ( Fr. Smith )
- Dorsal borders on the inside of the squamula curved outward . . . . . . . . . . . . 5

5. Outer border of the strongly downward sloping apical area of the volsella stretched out like a ridge to the back . . . . . . . . . . . . . . . . . . . . texana ( Buckley )
- Outer border of the strongly downward sloping apical area of the volsella not stretched out to the back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . insularis Guérin

6. Sagitta with broadenings to the sides ; side borders of the sagitta turned up or folded over to the inside ; apex narrowly convex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ( subgenus Neoatta Gonçalves ) 7
- Sagitta without broadenings to the sides ; side borders of the sagitta not turned up or folded over to the inside ; apex widely convex , turned over to the front , on both sides with a fingerlike extension . . ( subgenus Palaeatta Borgmeier ) 12

7. Sagitta , seen from above , sheath-like , side parts vertical . . sexdens ( Linn. )
- Sagitta , seen from above , looking almost like a spoon , side parts forming an obtuse angle with the middle part , top borders folded over to the middle . . . . . 8

8. Apex of the sagitta not stretched out to the back above the folded-up side borders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
- Apex of the sagitta stretched out to the back above the folded-up side borders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

9. The folded-up sides borders of the sagitta short and small . Subgenital plate at the distal end curved to the inside . . . . . . . . . . . . . . . . . . . . . . robusta Bogmeier
- The folded-up sides borders of the sagitta longer and broader . Subgenital plate at the distal end straight and strongly sloping downward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . laevigata ( Fr. Smith )

10. Sagitta broad , seen from above strongly diverging to the base ; the folded-up side borders of the sagitta on the inside not curved in . . . vollenweideri Forel
- - Sagitta smaller and longer , less strongly diverging to the base ; the folded-up side borders on the inside curved in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

11. The folded-up side borders of the sagitta short and small ; tip of the middle part only a little protruding . . . . . . . . . . . . . . . . . . . . . . . . . opaciceps Borgmeier
- - The folded-up side borders of the sagitta long ; tip of the middle part more strongly protruding to the rear . . . . . . . . . . . . . . . . . . . . . . capiguara Gonçalves

12. Stipes , seen from above , very broad ( subapically ½ times as broad as long ) , at the apex strongly sloping downward . . . . . . . . . . . . . . . . goiana Gonçalves
- - Stipes small , apically pointed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

13. Stipes as long as the volsella ; fingerlike extensions on both sides of the apex of the sagitta short . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . bisphaerica Forel
- - Stipes much shorter than the volsella ; extensions on the sides of the sagitta longer and broader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . saltensis Forel

Queens :

The queen of A. goiana Gonçalves is unknown .

1. Wing at the side of the costa with brown lines . . . . . . . . . . . . . . . . . . . . . . . . 2
- Wings at the side of the costa without brown lines . . . . . . . . . . . . . . . . . . . . . 6

2. Occipital corners without a tooth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
- Occipital corners with a tooth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3. Head width 5.2 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cephalotes ( Linn. )
- Head width 4.2 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. Body rust yellow , with against the body lying pubescens . . colombica Guérin
- Body dark brown , with outward projecting hairs . . . . . mexicana ( Fr. Smith )

5. Scutellum with a grove . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . insularis Guérin
- Scutellum without a grove . . . . . . . . . . . . . . . . . . . . . . . . . . texana ( Buckley )

6. Gaster smoothly polished , heavily shining ; head and thorax weakly shining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . saltensis Forel
- Gaster dull or weakly shining ; head and thorax dull . . . . . . sexdens ( Linn. ) , capiguara Gonçalves , vollenweideri Forel , laevigata ( Fr. Smith ) , opaciceps Borgmeier , robusta Borgmeier and bisphaerica Forel ( T. Borgmeier didn’t succeed in the dichotomous differentiation of the queens of these species ! ) .

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