as adult workers, they adopt their new “household” and 
do the foraging for the entire nest. A Polyergus nest, 
therefore, contains the Formica “slave” workers that 
come and go freely and the Polyergus workers that 
spend most of their time inside the nest. 
17. Prenolepis Mayr 
The single native North American species, P. 1m paris 
(Say), occurs commonly throughout Illinois. The 
workers are dark brown and 2-4 mm in length. 
These aphid tenders and general scavengers forage in 
hin columns and build their inconspicuous nests in the 
sround. ‘They are frequent pests in houses and green- 
jouses, eating a variety of domestic foods and sometimes 
snawing the tips of flower buds and the shoots of plants 
or their juices. They take honey from weakened bee- 
lives. 
(8. Paratrechina Mutschoulsky 
The genus is represented in Illinois by three species, 
ncluding two native species resembling Prenolepis im- 
aris in general appearance and an introduced species, 
aratrechina longicornis. This latter is also small and 
lark but has very long, slender legs and a peculiar rolling 
ait when running, earning the species the common name 
f crazy ant (Fig. 21). 
All of these species nest in the ground and may be 
eneral nuisances in the house, eating a variety of foods. 
ubfamily PSEUDOMYRMECINAE 
9. Pseudomyrmex Lund 
The five or six native American species occur south of 
llinois chiefly in the Gulf states and into the tropics. The 
orkers are 4-10 mm in length, mostly yellow or brown, 
nd wasplike in appearance. Some nest in hollow thorns 
n acacia trees; if the tree is disturbed, the workers dash 
ut and inflict painful bites and stings. 
ubfamily MYRMECINAE 
This is a large and diverse subfamily that is especially 
oundant in the tropics. The Illinois fauna is quite 
nall compared with that of the entire world. 
). Atta Fabricius 
This and the following genus belong to a New World 
ibe called the leaf-cutting ants. The reddish-brown 
orkers cut off pieces of leaves, carry them into the nest, 
ork them into a pulpy mass, and seed them with fungus 
ores. The ants feed only on the fungus produced by 
ese underground gardens. A mature colony contains 
ousands of individuals, including a large-headed soldier 
ste and several sizes of workers. The ants forage in 
lumns; a column of returning workers is a curious 
sht, each ant carrying a piece of leaf nearly as large 
itself. This leaf-carrying habit has earned these ants 
€ name of parasol ants. 
The leaf-cutting ants are almost entirely tropical, 
ith two genera extending northward into the south- 
ntral states. The genus Atta occurs north to central 
uisiana. 
19 
21. Trachymyrmex Forel 
This small genus is represented in Illinois only by 
T. septentrionalis (McCook), the northern leaf-cutting 
ant. It occurs only in sandy soil and makes relatively 
small nests, each having only a few hundred workers, 
22. Strumigenys F. Smith 
This and the following genus belong to a worldwide, 
distinctive tribe of minute ants whose workers and queens 
have long, pointed heads. The workers are dark reddish 
brown and range in size from 1.5 to 2.5 mm, They oc- 
cur only in wooded areas, making small nests in rotten 
wood and foraging in leaf mold. They feed on spring- 
tails and other minute organisms. The sole North Ameri- 
can species of this genus, S. louisianae Roger, occurs in 
Illinois (Fig. 24A and B). 
23. Smithistruma Brown 
Several species of this genus occur in Illinois wood- 
lands. In general habits and appearance they resemble 
Strumigenys, but have shorter mandibles (Fig. 24C and 
DD atign 2 oye 
24. Wasmannia Forel 
This genus is represented in North America and IIli- 
nois only by W. auropunctata (Roger), an introduced 
tropical species that occurs this far north only in houses 
or greenhouses. The dark workers are minute, only 1.5- 
1.8 mm, but sting severely, earning them the name little 
fire ants. They nest in soil and under cover, often with 
several queens and several thousand workers in a nest. 
They feed on honeydew, minute insects, and a wide 
variety of domestic foods. 
25. Harpagoxenus Forel 
Of the two North American species only H. ameri- 
canus (Emery) is known from Illinois. The reddijsh- 
Fig. 24.—Front views of heads of workers. A, B, Strumigenys 
loutstanae Roger, showing variation; C, Smithistruma angulata 
Smith; D, Smithistruma pergandei Emery. Inset are details of 
the mandibles. (After M. R. Smith) 
