_ they were working considerable mischief by killing the young plants. As observed. 
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148 REPORT OF THE COMMISSIONER OF AGRICULIURE, : 
\ \ x 
TEE TWELVE-SPOTTED DIABROTICA, ; ve 
(Diabrotica 12-punctata.) : Rae: 
“While in the South during the spring of 1886 we frequently heard of fields of. 
young corn being seriously injured, during some seasons, by a small white worm 
which attacked the roots, usually during April. From the description givenusof  ° » 
the pest and its manner of attacking the plants, we iirst thought it might be the_ 
larva of D. longicornis, as the habitat of that species is known to extend south- 
ward to Centrai America. ; 
On April 12 of the present year we were enabled to solve the problem by finding 
considerable numbers of these larvee in a field of corn in Tensas Parish, La., where - 
by us, their mode of attack differed from that of their northern congener in that "4 
they did not appear to attack the fibrous roots or bury themselves in longitudinal fe 
channels excavated in the larger roots. On the contrary, they burrowed directly 
into the plants at or near the upper whorl of roots, which almost invariably resulted — 
in the death of the plant. These larva: were much more active than those of 
longicornis, and on being disturbed would make their way out of their burrows and 
attempt to escape by crawling slowly into crevices in the soil, or if it were finely 
pulverized they would work their way down into it out of sight. Often several 
individuals, varying greatly in size, would be found about a single plant. On the 
20th of same month, in another field, we found the laryve much more numerous 
and the crop injured fully 75 per cent. Plants here, 6 to 8 inches high, were wither- 
ing up and discoloring. Both of these fields had produced cotton the preceding year. —_- 
The adult beetles were frequently seen before we observed the larvee, but they ’ 
were not abundant about the plants in the cornfields, being usually on the yellow ~ 
blossoms of a species of Aster which springs up in cultivated grounds early in the 
spring in great abundance. No pup were found, although careful search was 
made for them. We have elsewhere shown that the adult insect attacks leaves -of 
young corn in Indiana.* is 
THE CORN PLANT-LOUSE. 
(Riopalosiphum maidis.) 
So far as we are aware, this species is not recorded as injuring corn inany of the 
Gulf States. Considerable damage, however, is done by the root form in both 
Louisiana and Mississippi, and we observed the aérial form also in great abundance 
during June and July of the present year in both of these States. 
im October, 1885, we transferred some volunteer plants of corn from the field of 
fall wheat, where they grew, to some breeding-cages. The plants were thickly 
populated with winged femaies, and these were carefully secured with the plants, 
both being subjected to the same conditions which would have aflueneeen them 
had they remained in the field, except that the ants in attendance were excluded. 
On May 8, 1886, corn was planted in these cages and grew therein tll after the 
15th of June without a single individual of either root or aérial form being on or 
about the plants, and they were then thrown out. 
In the meantime corn had been planted indoors in pots, and on June 24 these were 
placed in a field where serious injury was being done by the rcot form of the Corn: 
Aphis. The pots were buried in the earth between the rows until the soil within 
was ona level with, and not obstructed in the least by, the tops of the pots, from the 
surface of the ground. Several hills seriously infested. were puiled up in the vicinity 
of these pots, thereby exposing both roots and plant-lice to the sun. 
The next day the ants were burrowing about the plants in the pots, and a few 
days later the roots were well stocked with lice, many of them being full-grown. 
Besides this we had observed ants with lice in their mouths overa yard distant from 
the hills which had been pulled up, thereby indicating that the bereft were supplied 
with homes on the neighboring hills as well as on the potted plants. 
Grasses and other plants were examined during the autumn, but no distinguish- , 
able corn-plant lice were obtainable. 
The present season we were absent from home from the middle of March until 
after the 20th of May. On the 27th of this month, however, we found winged, 
viviparous females on the roots of corn in a field planted on the 18th instant. A 
thorough search revealed the fact that the wingless lice weve all very small. A 
heavy rain had’fallen on the 23d, and it was only -vhere fresh mounds thrown up 
*TIndiana Agricultural Report, 1885, p. 198. 
