20 
Fig. 25—Worker of Strumigenys ohioensis Kennedy and 
Schramm, showing the soft, white, funguslike growths that 
occur on the petiole in many species of this genus. Actual size, 
29mm. (After Kennedy and Schramm) 
brown workers are fairly large, ranging in length from 
3.0 to 3.5 mm, and forage in leaf mold, under bark, and 
on low vegetation. This species does not make a nest 
of its own. Instead, it takes over nests of the genus 
Leptothorax. The Leptothorax queen is killed, and the 
Leptothorax workers then assist in raising the brood of 
the Harpagoxenus queen. This genus does not normally 
inhabit gardens or houses. 
26. Crematogaster Lund 
Several native species of this genus are extremely 
common in Illinois. The workers (Fig. 26) usually have 
red heads and black abdomens, and range in size from 
9.5 to 4.0mm. They are easily recognized by the broad 
head and wide, heart-shaped gaster. These ants nest 
under stones or other objects on the grourid, in dead 
stumps or logs, and sometimes in posts and rafters, but 
never in the ground. The colonies may contain several 
thousand workers. They are general foragers and abun- 
dant both in the garden and house, feeding on a variety 
of domestic foods. In the garden they are often found 
tending aphids. When disturbed, they bite and sting 
painfully. 
27. Solenopsis Westwood 
The only Illinois species of this genus is the native 
S. molesta (Say). The workers are dark brown and 
minute, ranging from 1.3 to 1.8 mm. The nests are 
usually deep in the ground and each may have several 
Fig. 26.—Worker of Crematogaster lineolata 
(Say). A, side view; B, dorsal view of petiole 
and gaster. 
thousand workers. These are among the commones 
of garden and household ants, feeding on a variety ¢ 
domestic foods and often eating garden seeds. 
To this genus also belong the fire ants, several specie 
of which occur south of Illinois. These ants are chiefl 
agricultural, and when disturbed, bite and sting pair 
fully. 
28. Monomorium Mayr 
The two Illinois species of this genus, the native 
minimum (Buckley) and the introduced Pharaoh’s an 
M. pharaonis (Linnaeus) (Fig. 27), are among ot 
tiniest ants, the workers ranging from 1.2 to 2.0 mr 
Both species nest in the soil or in buildings and ai 
frequently abundant in houses, where they eat a varie 
of domestic food. Pharaoh’s ant is especially fond of fat 
The introduced species, M. destructor (Jerdon), occu 
to the south of Illinois and may eventually be found 
the state. It also is a domestic pest that causes troub 
by removing insulation from electric cables and cuttir 
holes in fabrics and rubber goods; it also inflicts a pai 
ful sting. 
Kry ro Species oF MonoMorituM WoRKERS 
1. Segments of the antennal club successively increé 
ing in‘length .;.......2 ego destruct 
First two segments of the antennal club about t 
same size, the terminal segment larger ..... 
9, Clear reddish yellow .....-..22 455578 pharaoi 
Shining black ......... 2) eee minimu 
29. Pogonomyrmex Mayr 
The ants of this genus are the native agricultural ai 
famous throughout the Great Plains. None has so } 
been taken in Illinois, but they are known not * 
to the west. The workers are chiefly reddish brown a 
large, ranging from 4.5 to 12.0 mm in length. They n 
in the ground, constructing a mound of gravel son 
times 45 cm in diameter and clearing all vegetat 
around it to a distance of about 1 meter. When ¢ 
turbed, the workers have a potent sting. These a 
feed chiefly on seeds supplemented by general scavel 
ing. 
30. Aphaenogaster Mayr 
This large native genus is represented in Illinois 
about six species. 
The workers are very slender a 
