10 Annals Entomological Society of America |Vol. VIII,. 
vitality in the victims, but we can only guess at possible causes. 
of decrease in their powers of resistance; and of these disease- 
producing fungi we know too little, either of their effects, of 
the comparative virulence of the various species, of variations. 
in the virulence of different strains of the same species, or of 
the possibility of increasing their effect by selective cultures. 
of the most virulent varieties. 
We know that the chinch-bug is strictly.limited for food to: 
plants belonging to the grass and sedge families, but we do not 
know why it can not feed—refuses even to try to feed—upon 
other plants, although prompt starvation is the alternative;. 
nor do we know why it plainly prefers some of its natural food- 
plants to others, and why it thrives best and multiplies most 
rapidly upon those which it prefers. We do not even know by 
what tests or senses it distinguishes its favorite foods or avoids. 
those upon which it can not live. 
We have noticed, where this insect sweeps in hordes across 
a field, infesting all plants substantially alike, that here and 
there one may stand alive and erect while all its companions 
have perished; but we do not know why this should be so or 
whether by a selection of such escaping victims we might 
breed repellant or resistant lines, increasingly capable of with- 
standing attacks destructive to the average of their kind. 
We know the ordinary life history of the chinch-bug fairly 
well, although our knowledge is still lacking in the details of 
variation of life history in different regions, seasons, and cli- 
mates; while of its so-called physiological life history we know 
almost nothing exact. 
We know that an invaluable opportunity is afforded us at 
harvest time to destroy the pest as it attempts to escape on 
foot from the dry wheat stubble. We know that a line of crude 
creosote poured upon the ground is practically impassible by 
it, and that this simple fact of ordinary observation may be 
utilized to arrest its dispersal and, by the addition of post-hole 
traps along the line, to capture and destroy it by bushels and 
barrels and even by wagon-loads; but we do not know what it 
is in the creosote line which makes it seemingly impassible, 
since occasionally, or under extraordinary compulsion, the 
insects cross it without the slightest injury. Consequently, 
in our search for more desirable substances for this use we have: 
