388 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



merits in literature regarding the dispersion of the adults bj^ flight to 

 parts of the field distant from the food trees, the long flights observed 

 are probably made by the males, for almost invariably grubs are most 

 abundant near the food supply of the adults. In fields half a mile, or 

 even quarter of a mile long, grubs will be abundant in the end near trees, 

 and practically absent at the other end if no trees are near. Of course, 

 grubs are not always abundant near trees, even when all other condi- 

 tions seem favorable, and occasionally solitary grubs are found in 

 fields a mile or more from the nearest food tree, and sometimes these 

 grubs are parasitized, but these are exceptions. The comparative 

 absence of trees throughout large areas of the more fertile and more 

 valuable portions of Illinois, probably is the most important factor in 

 limiting the abundance of Lachnosterna. If an abundance of grubs 

 were to be found in most fields, the dispersion of Tiphia females would 

 be greatly facilitated from a field in which most of the grubs have 

 been parasitized, but as the supply of grubs is usually localized to a 

 small area near a woods or clump of trees, the Tiphia remain in this 

 locality, destroying all the grubs, and are themselves destroyed by the 

 fungus which can more easily cause an epidemic among its crowded 

 hosts, or else they perish without ovipositing while traveling to distant 

 fields in search for grubs. 



Practically all the fields from which the largest numbers of Tiphia 

 cocoons have been collected were of these two types, either with several 

 large cottonwood trees in the field or in a nearby hedgerow (near 

 Champaign, Randolph, Wapella, Minooka, Hendrix, 111.) or near oak or 

 mixed woods (near White Heath and Monticello, 111.). From only four 

 other fields have collections of any size been made and these were of 

 minor importance (near Rantoul south, Rantoul north, Monticello, 

 Cerro Gordo, 111.). Even in these cases, cottonwoods, willows, oaks 

 or elms were not more than cjuarter of a mile away, and in at least two 

 instances the fields had been unpastured meadows for several years 

 prior to being plowed. In the great majority of all the fields, the 

 plowing was for corn (5 to 7 inch deep) on land that had been in sod 

 (clover, red and alsike, or grass) for two or more years and had not 

 been pastured. The deep plowing made collection of cocoons possi- 

 ble and the other factors were of importance in producing an abund- 

 ance of grubs — a potential host supply for a subsequent abundance of 

 Tiphia. 



In the more hilly and wooded sections of Illinois, the soil is not the 

 typical black clay and brown silt loam of central Illinois, but is a gray 

 clay of poorer texture, or a sandy, gravelly loam. To both of these 

 types of soil another parasite of Lachnosterna, Elis sexcincta Fabr., 

 seems to be better adapted, for in collections made near Galesburg, 



