16 
PS) 
26. 
203 
28. 
20: 
30. 
able 
aye 
33: 
oa. 
Fig. 21.—Worker of the crazy ant, 
Prenolepis longicornis. (After Wheeler) 
10K) ; clypeus shallow, its apical margin concave 
(Fig. 10L) 29. Pogonomyrmex 
Head and body with a few erect hairs, but these 
are never long or numerous; clypeus deeper and 
O00 foc debe cio m tio 
somewhat convex (Fig. 10M) .......--+-+-- 748) 
Antenna 11 or 12 segmented ..........+-+++:- 26 
Antenna 13 segmented .........----+++es0e> 20 
Petiole attached high on anterior face of gaster; 
segments of funicle appearing somewhat bead- 
like 26. Crematogaster 
Petiole attached low on anterior face of gaster; seg- 
ments of funicle not at all beadlike ......... 27 
First funicular segment enlarged, often globose, 
scape very short (Fig. 16J) ...-.-. 27. Solenopsis 
First funicular segment not markedly enlarged, 
scape longer, as in Fig. 16K .....-.----+-: 28 
Antennal scrobes well developed (Fig. 10£) 
Be ea eer Poet 25. Harpagoxenus 
Antennal scrobes weakly developed or absent 
ees RAS A Oa neat ee 36. Leptothorax 
Mandibles vestigial, reduced to short fleshy stubs 
(Fig 16D) ean ste ae 31. Myrmecina 
Mandibles developed and _ sclerotized, although 
sometimes small {so sername yee eee 30 
Abdomen in lateral view with a pair of elongate 
processes (the parameres of the genitalia) pro- 
truding from the posterior tip (Fig. 16P) 
NO Pe yr a rr spaced Sy, ns eo 24. Wasmannia 
Abdomen with only short protruding processes, 
which are blunt at the tip, or no visible pro- 
truding structures 
Scape very long, at least as long as the first eight 
funicular segments combined .........----- 32 
Scape shorter, not as long as the first eight funicular 
segments! 2 = sacs sires hae ee ee op) 
Front wing with cell R; short and wide (Fig. 22B) 
SOb AMEN Oli: AF ee 21. Trachymyrmex 
Front wing with cell Ri long and narrow (Fig. 22A) 
A MEE Ske OO SAECO oe, Nene 20. Atta 
Stigma of forewing weakly developed or missing 
(males too poorly known to permit further iden- 
tification without other castes). . 22. Strumigenys 
23. Smithistruma 
Stigma of forewing well developed, as in Fig. 16B, 
but sometimes pale 3.00 oy-emene ee ee 2 
Head flattened and either shallowly elliptic (Fig. 
16M) or almost rectangular in lateral view (Fig. 
OCH aC) Catharh Gilda cece DarD Gecugs Ol OG 
16N) 
Head much more rounded 
35. Base of clypeus ending in a marked semicircular 
depression (Fig. 10/) 34. Myrmica 
Base of clypeus ending in a shallow triangular im- 
pression, or no depression evident .......... 36 
36. Body of scape very short, at most as long as the 
first and second funicular segments combined 
eee © 10; le fe, 16, oF 
Body of scape longer than the first and second funi- 
cular segments combined ...........-++++: 38 
37. Funicle threadlike, the same thickness for its entire 
length; ocelli on a high protuberance (Fig. 16F) 
33. Pheidole 
Funicle with last four segments much thicker than 
first few segments; ocelli not on a protuberance 
28. Monomoriur 
38. Ocelli small, separated from each other by twice the 
diameter of one of them (Fig. 16C) ; epinotur 
concave in lateral view........ 32. Stenamm 
Ocelli large, separated from each other by only thi 
diameter of one of them, somewhat as in Fig 
16E; epinotum convex in lateral view 
36. Leptothora: 
ob vee cee eve ve) Woe fee! 0 co: .#) (0: 0) Jo) tan Smee) 19s 
bi oer joe Sensor fei Let ve 8) vere, te, 8 rer in) @@) 0) ou uns tnan ene 
SYNOPSES OF GENERA 
Subfamily ECITONINAE 
These ants are the native American army ants, differ 
ing in many characters from the army ants of the Ol 
World. The New World species occur chiefly in th 
tropics, where the workers may form long foraging col 
umns. Their food is mostly other insects and sma 
ground-dwelling animals, but they may kill fairly larg 
animals. The nest is a temporary bivouac built aroun 
the queen and brood. Only two genera occur in or nez 
Illinois. 
1. Labidus Jurine 
No species have been recorded from Illinois, but 1 
coecum (Latreille) is known from Louisiana, Oklahom: 
and Texas and may eventually be found in Illinois. TI 
workers range from 3 to 10 mm long, the larger on! 
with slightly enlarged heads. 
2. Neivamyrmex Borgmeier 
The southern and southwestern species, N. nigresce 
(Cresson) , has been found sporadically in extreme soutl 
