ern Illinois, where it may be an occasional pest in swim- 
ming pools and basements. In this species the workers 
are 3-6 mm long and dark blackish red, the larger ones 
with slightly swollen heads. Several other species occur 
to the south and west of Illinois. 
Subfamily PONERINAE 
The ants comprising this subfamily are seldom found 
without a deliberate search of rotten logs or beneath 
leaves and stones on the forest floor, They both forage 
for small prey and nest in these situations. The nests 
are small, rarely containing more than 50 workers, and 
each nest may contain several queens. The workers and 
queens are reddish or reddish brown, range from 2 to 
6 mm in length, and have a sting. 
Of the 12 or more genera known from North Ameri- 
ca, the 4 more northern ones have been taken in Illinois. 
None of the Illinois species is economic. Only rarely 
are any of them found in the garden or home. 
3. Amblyopone Erichson 
The sole Illinois species, A. pallipes Haldeman, (for- 
merly placed in the genus Stigmatomma Roger) is the 
only one known from North America. It. is readily 
recognized in the worker and queen castes by the elongate 
mandibles (Fig. 7F). Although widely distributed in 
Illinois, it is a rare species. 
4. Ponera Latreille 
This is the commonest ponerine ant genus in Illinois, 
where two of the seven North American species occur. 
The genus is unusual because some colonies produce 
wingless, workerlike males. 
5. Proceratium Roger 
Of the three North American species, only P. croceum 
Roger has been found in Illinois. It is a rare species 
whose nests are usually found in wood attacked by red 
rot. 
56. Sysphincta Roger 
Of the two North American species, only the wide- 
spread S$. pergandei Emery has been found in Illinois. 
[t is moderately rare. 
Subfamily DOLICHODERINAE 
These ants have no sting and the workers are all 
ike, with no larger soldier caste. Four of the six North 
\merican genera occur in Illinois; all of them are small, 
rownish or blackish ants, the workers ranging from 2.0 
045 mm. Colonies usually contain several hundred 
ndividuals. All Illinois species forage in files. 
. Dolichoderus Lund 
Two of the four U.S. species occur in Illinois. Their 
lest, made in the soil, is not craterlike and has a con- 
ealed opening. They are not economic and are seldom 
fen outside woodlands or forest edges. Dolichoderus 
s often found tending aphids. 
» Dorymyrmex Mayr 
The sole North American species, D. pyramicus, has 
> far been collected in Illinois only in undisturbed 
17 
oe 
ee 
ee e 
e cee 
oc e? e Oe 
Fig. 22.—Wings of leaf-cutting ants. A, Atta sexdens Lin- 
naeus; B, Trachymyrmex cornetzi Forel. (After Weber, courtesy 
of Science) 
sandy areas. The nest is usually in the open and crater- 
like, but occasionally is constructed under stones. 
9. Iridomyrmex Mayr 
Two species occur in Illinois, the introduced species, 
I. humilis (Mayr), (the Argentine ant) (Fig. 18) and 
the native J. pruinosus (Roger). In both, the workers 
are small, ranging from 2 to 3 mm long. Both species 
nest in soil or under stones or boards. The workers for- 
age in narrow columns, often tend aphids, and eat a 
wide variety of vegetable and animal foods. 
The Argentine ant is a domestic pest, entering houses 
and eating all types of sweets, meats, and vegetables. 
When crushed, the ants have a stale, greasy or musty 
odor. 
Key To Species or IrRtpoMyRMEX WORKERS 
Scape extending beyond top of head by only half the 
length of first funicular segment. Seldom in houses 
pruinosus 
Scape extending beyond top of head by the full length of 
first funicular segment. Frequently in houses 
humilis 
ep dem ehS est Sus tim= x OnMa We esi, ern Gr ef eY Lo ical oy lataieu tet iages” fer eumeiivnosy aioe 
oe ck whee Oe ci PENS DC REST ee sie tiec ecw: el. aieine Terie) isis tel ie Female), topre nak ome mente: ie 
10. Tapinoma Foerster 
Only the native species, T. sessile (Say), occurs in 
Illinois. It is a small ant, the worker ranging from 2.0 
to 3.5 mm, and it is dark blackish brown. It nests in 
a great variety of sheltered places inside the house and 
outdoors, often with several thousand workers in a single 
nest. ‘The species is practically omnivorous. Common 
in dwellings, it will eat almost any human food and con- 
taminates foods with “Tapinoma odor,” a smell some- 
what like butyric acid that has earned this species the 
name of odorous house ant. 
Subfamily FORMICINAE 
Ants of this subfamily range from nearly the smallest 
to the largest of Illinois ants. The queens and workers 
have no sting but are characterized by the curious circle 
of hairs around the anal opening. 
