68 



extends over a considerable period. Here in the District of Columbia 

 the present year the first beetles that were noticed appeared late in 

 April. 1 Larvae were first noticed hatched May 11, but eggs were still 

 to be found late in June. 



Eggs deposited May 11 and 12 hatched Ma} T 19 and 20, or in eight 

 days, the weather during this time being seasonable. 



Larval habits. — The plants of dock on the Department grounds upon 

 which beetles were placed were carefully watched and the stems and 

 roots were pulled up for examination from time to time, but, unfor- 

 tunately, the ants which were associated with aphides at the roots 

 entered the burrows and killed the larvae, thus interrupting our 

 experiments. Stems of dock were also examined in the neighborhood 

 about the District of Columbia and larvae were found to approach 

 maturity during the first and second weeks in July. July 22 an imma- 

 ture beetle was found in its burrow, larvae and pupae also being present 

 in that vicinit}^ at this time. The duration of the larval stage, although 

 not definitely ascertained, is not far from two months. 



It is probable from all that could be learned that larvae begin to 

 approach maturity about the first or second week of July. 



Beetles put in our rearing cages in early May lived through June 

 till about the middle of July, some, however, dying earlier; in other 

 words, some of the hibernated beetles are still living within a few days 

 of the time of the first appearance of the new generation. 



In the stems of dock examined, only a single Lixus was found to 

 develop in a stem. Often a dozen or more punctures are made in a 

 stem and nearly as many eggs are deposited in some cases, but one 

 larva only develops. What becomes of the other larvae is a problem. 

 Presumably they fall a prey in many instances to predaceous insects, 

 particularly ants, but when they are not so destroyed it would seem 

 that they either die from being shut off by the larva nearest the roots 

 into the upper portion of the plant, where they succumb with the dying 

 of the stem, while the lowest larvae, having an abundance of moist 

 food, survives. Very often the larvae bore down into the root, evi- 

 dently being driven to this expedient by the drying of the stems above. 



Life cycle still incomplete. — From the above it will be seen that the 

 full life cycle is not yet known. The egg stage, as previously observed, 

 was eight days in seasonable May weather. The observed duration of 

 the pupal period in the hot weather of July was also eight days. The 

 observations on the life cycle period, and hence the larval period, which 

 could readily have been made out by. deduction, were interrupted by 

 the ants. 



The species does not appear to develop in rhubarb. — If the larva lives 

 at all in rhubarb this fact has escaped observation. Many eggs fail to 



'This is true, also, of L. mucidus, according to Weed. 



