69 



hatch, presumably being destroyed by the superabundance of juice 

 which exudes from the plant where egg deposit takes place, while the 

 larva?, if the} T hatch at all, meet death in the same way. 



Of all of the many thousands of eggs of this species that were 

 deposited within a few miles of the District of Columbia it is obvious 

 that only hundreds produced beetles. None that were deposited in 

 rhubarb appeared to develop. A large percentage that were laid in 

 dock and that produced larvae also died before attaining maturity. In 

 addition to ants, parasitic insects must have destroyed their quota of 

 larvae. So it follows that, taking into consideration the number of 

 beetles that fail to survive the winter, the species, compared with 

 many others that could be mentioned, leads quite a precarious existence. 



NATURAL ENEMIES. 



Mr. Webster, writing of this curculio in stems of Helianthus, 

 remarked that a great many of the larvae were devoured by wood- 

 peckers. Dr. Weed recorded the rearing at Columbus, Ohio, of a 

 hymenopterous parasite of Lixus mucidus, Bracon rugator Say. These 

 parasites develop at the expense of the larvae, feeding externally upon 

 them. When mature they spin brown silken cocoons in which to 

 transform. As several Braconids are known to be parasitic on other 

 species of Lixus feeding like the present one in stems, it is probable 

 that one or more species attack Lixus concavus. 



REMEDIES. 



The use of arsenicals or other poisonous insecticides upon rhubarb 

 during its growing season is of course out of the question. Fortunately 

 the nature of the injury by the species is not as a rule serious. When, 

 however, this curculio occurs in troublesome numbers it can readily 

 be controlled by other methods. The beetles are so large and con- 

 spicuous, and so often occur freely exposed in the bright sunlight on 

 the leaves, that they are easily detected, and as they are sluggish and 

 do not fly readily there is no difficulty in capturing them. The proper 

 time for this is upon the beetles' first appearance. It would be well 

 also to gather the beetles upon near-by plants of dock, and after the 

 eggs are deposited these plants should be pulled up and burned. In 

 the District of Columbia and in similar latitudes the beetles are to be 

 looked for toward the end of April and first of May, and the docks 

 which serve as a trap crop should be destroyed about the first of 

 July, as most of the eggs have been deposited by that time. 



