45 



of the poisoning experiments contemplated. The principal remedies studied were 

 the use of trap rows and the destruction of the tobacco stalks and stubs. The results 

 obtained may be stated briefly as follows: 



Among cultivated crops Trichobaris mucorea attacks both the Irish potato and 

 tobacco. It feeds upon horse nettle (Solarium carolinense), but its particular and 

 almost exclusive wild food plants are the two jimson weeds (Datura stramonium 

 and D. tatula ) , the latter quite common at Willis. Since both Daturas are introduced 

 weeds, it is evident that the weevil fed originally upon some other plant. There is 

 a native Datura (D. meteloides) in the Southwest, and, as Mr. Schwarz has taken 

 Trichobaris mucorea from it in Texas and Mr. Coquillett also in California, this is 

 without doubt its original food plant, and its occurrence at Willis indicates an exten- 

 sion of its range following the introduction of the other species of Datura. 



The mature weevil, as a rule, hibernates in the stalks of tobacco or jimson, emerg- 

 ing in the spring when the weather is warm enough for the growth of the somewhat 

 tender Solanacese. This year, which in Texas was nearly a month behind the usual 

 season, the weevils were found feeding in the field in the middle of April. After a 

 feeding period of a few days they copulate and oviposition begins. In the jimsons 

 the egg is laid in the forks of the branches, but in tobacco at the lower side of a 

 midrib of a leaf where it joins the stem. The larva may succeed in penetrating at 

 once to the pith, and in tobacco bores out the pith from the root to the tip of the 

 stem, producing a stunted " cabbage" plant in which the stem stops growing and all 

 the leaves are produced in a kind of head on the short stem. The more usual 

 course, however, is for the larva to wander about for a time just under the bark. It 

 is not unusual for it to complete its transformations without penetrating to the 

 pith at all. The course of the larval tunnel is usually irregularly spiral and the 

 whorls are frequently so near together as to produce a girdling of the stalk, an effect 

 known to the planters as "ring worm." This girdling may not particularly injure 

 the plant, but frequently the plant is so deeply cut and so weakened that it is likely 

 to be snapped off by strong winds. Ordinarily the insect's transformations are com- 

 pleted in the pith. When this is the case the fully grown larva cuts a cylindrical 

 hole through the wood to the bark and uses the woody particles thus obtained to 

 construct its pupa case. The life cycle was not observed, but it was estimated that 

 this period did not exceed 75 days. Apparently there is only one brood in a season, 

 the weevil maturing in June or July and in some cases probably later, remaining in 

 the tobacco or jimson stalk if undisturbed until the next March or April. 



Two other species of Trichobaris were found at Willis and their habits observed. 

 These are T. texana Lee, boring in the larval condition in the stems of bull nettle 

 (Solatium rostratum), and T. compacta Casey, breeding in the seed pods of the jim- 

 sons. These species may readily be mistaken for T. mucorea by one not familiar with 

 insects. 



It is hardly feasible to poison the weevils upon tobacco by means of a spray, since 

 they feed almost exclusively upon the under sides of the midribs in a position almost 

 impossible to reach by spraying. They might be reached by dipping the plants in 

 a solution of lead arsenate when they are planted out. Poisoning on trap rows of 

 jimson or potatoes by means of a spray would be effective if done thoroughly, for on 

 these plants the weevils ordinarily feast upon the upper side of the leaves. 



Ordinarily there will be but little use of trap crops, but undoubtedly considerable 

 benefit would be derived by planting a trap crop of jimson or Irish potatoes in cases 

 where the proper care has not been exercised in destroying the weevils. Perhaps 

 the potatoes would be preferable, and they should be planted very early and then 

 thoroughly sprayed a few clays before the tobacco is planted out. 



The main reliance in all cases should be the burning of all stalks and stubs of 

 tobacco and jimson. The sooner this is done after the tobacco is cut or pruned the 

 better, for some of the weevils will emerge from the split and broken stalks and hiber- 



