2 OHIO EXPERIMENT STATION: BULLETIN 197 



attacked that from one-third to one-half the leaves wilt, turn brown 

 and die from this cause. After the larvae disappear from the leaves, 

 the resemblance of these spots to some of the fungous leaf-spot 

 maladies is so great that for one or two seasons our botanists examined 

 the spots very carefully at intervals with the compound microscope, 

 the only result being to strengthen the suspicion that they were in 

 some way caused by insects. The spots are generally about three- 

 sixteenths of an inch in diametef", but vary from mere points of 

 brown to more than one-fourth inch in diameter, and sometimes by 

 the coalescence of numerous spots large irregular patches of dead 

 tissue are formed. Late in the season many of the spots break 

 through or fall away, leaving the leaf full of holes and torn and 

 ragged in appea,rance. That the larvae causing this trouble are 

 identical with those which work in the bud seems quite certain by 

 their similar appearance of form and coincident period of 

 attack, but we have not yet bred leaf larvae from adults known to 

 have developed from bud-inhabiting larvae, or vice versa, so the 

 proof of their supposed identity is not perfect. But few la/vae have 

 been found on the leaves of old trees in the fall, the attack being 

 apparently concentrated on the seed pods; but young trees have 

 many larvae on their leaves in mid September, and probably until 

 the leaves fall. 



2. The most conspicuous form of injury due to the midgp and 

 the one which has been the subject of most inquiry at the Station is 

 that done to the terminal buds. Mr. Cotton writes thus of his 

 observations in 1905: "At several points in southwestern Ohio, 

 injury to the tender tips of vigorously growing two-and three-year- 

 old catalpa trees in nursery rows was observed during August and 

 September, 1905. Usually two or three inches of the tips began to 

 wither and turn brown, finally becoming much shrunken and black. 

 When opened they were found to contain several small, yellow, > 

 footless maggots, similar to the catalpa pod Diplosis, and having the 

 same power of leaping. The eggs were apparently deposited in the 

 stem at the base of a leaf petiole or in the petiole base itself, and the 

 stem began to die at this point." 



"In one small block of two-year-old catalpas, about twenty-five 

 percent of the trees had been injured. They had been cut back to 

 the ground the previous spring and as a consequence had made a 

 very vigorous growth. Many of them had been injured while still 

 quite small, and in nearly every case all three of the lateral buds, at 

 the last lomt below the point of injury, had attempted to produce a 



