386 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 







weather and to the attacks of birds and predaceous mammals and 

 insects. 



Ecology 



The various species of Lachnosterna in the Middle West are attacked 

 by a considerable number of parasites and predators, but undoubtedly 

 Tiphia inornata is the most important. I am convinced that under 

 favorable circumstances Tiphia does greatly reduce the numbers of 

 grubs and in some cases practically exterminates Lachnosterna from 

 limited areas. The evidence is this: In some fields (near Randolph, 

 Hendrix, White Heath, 111., and at many other places) one will find 

 many cocoons from which adults have emerged, a few in which adults 

 are contained, and a very few grubs or beetles. Or in fields in which 

 practical extinction of the grubs has taken place a year or more ago 

 (near Weldon, Minooka, Seymour, Homer, 111., and at other places) 

 one can find only old rotten cocoons from Avhich adults have emerged 

 several months or a year previously, and few or no grubs and beetles. 



The adult femalefe of Tiphia are not strong fliers and they tend to 

 remain in the field where their immature stages have been passed. 

 When the grubs are abundant, no difficulty is experienced by the female 

 Tiphia in finding sufficient numbers for the deposition of a large number 

 of eggs. The rate of multiplication is rapid, for two generations of 

 Tiphia probably occur during the summer. The supply of non- 

 parasitized grubs in a field soon tends to become exhausted, necessitat- 

 ing a more careful search by the female to find a host for her eggs. 

 The female, loath to search at great distances, eventually parasitizes 

 practically all the grubs of suitable size in a field, until the dispersion 

 of the females to new localities is necessary unless large numbers are 

 to perish without depositing eggs. The males can fly long distances 

 and are often collected feeding on the flowers of goldenrod and asters, 

 but the females are less often found in these situations and apparently 

 have difficulty in flying any great distance. 



There are, however,' several checks to an unusuallj' great increase of 

 Tiphia in restricted localities. Under favorable conditions, a fungus 

 (probably Isaria sp.) causes a heavy mortality. Cocoons are often 

 found covered with a weft of white mycelium densely covered with 

 spores, spreading out into the surrounding earth. It has not yet been 

 determined how infection by the fungus takes place — Avhether the 

 spores only attack the parasite egg or maggot, or whether the mycelium 

 is able to penetrate the cocoon. It may be that the fungus attacks 

 Tiphia only when it is weakened by unfavorable conditions, such as 

 sudden changes in temperature or too much or too little moisture, and 

 is not pathogenic on healthy individuals. Naturally when Tiphia is 

 most abundant the fungus will have the least difficulty in spreading 

 and often nearly all the Tiphia in a field are killed in this way. 



