BUREAU OF ENTOMOLOGY. 317 



The investigations of pecan insects in the Southeast having been 

 fairly well completed, it seemed desirable to transfer the work in 

 the Southeast to Texas, which was done in June. Special attention 

 in that State will be given to the pecan nut case-bearer, which is 

 there very destructive, and also to the pecan weevil and other mis- 

 cellaneous pecan insects. 



Miscellaneovs mit insects in the North. — The walnut husk maggot, 

 Avhich fed originally and still feeds extensively in the husks of black 

 walnuts, is now attacking the husks of Persian and Japanese walnuts 

 in the eastern part of the country. The maggots in great numbers 

 mine through the husks, causing the nuts either to drop prematurely 

 or to adheix' to the branches beyond the regular harvest time. The 

 shells of the nuts are also stained and soiled by the maggots. In 

 several localities in Maryland and Pennsylvania very promising 

 crops of Persian waluuts have been practically ruined by this species. 

 A study of the life history, habits, and means of control of the husk 

 maggot is under way and results will be ready for publication by the 

 end of the season. 



Several species of walnut and hickory curcnlios are also under 

 investigation. These insects attack the immature nuts, causing many 

 of them to fall. Tlie walnut curculio attacks butternuts, Persian 

 walnuts, and Japanese walnuts, causing the nuts to drop prematurely, 

 and the grubs miue the tender shoots of the husks, frequently killing 

 young trees. Another form, C onot rachelus retentiif, lays its eggs in 

 black walnuts wlieu the nuts are about one-fourth grown, the larvse 

 causing the nuts to drop. By actual count it has been ascertained 

 that in some localities from 50 to 00 per cent of the nuts are infested. 

 The weevils attacking chestnut and hazelnut are also being studied. 

 Choice varieties of our native hazel are being introduced b}' nursery- 

 men and the present interest in growing hazelnuts makes a study of 

 the hazelnut weevil important. 



Orchard insecticide investigations. — Investigations of miscel- 

 laneous insecticides have been continued. A comparative study of 

 arsenicals as insecticides, in cooperation with the Bureau of Chem- 

 istry, has been under way during the past two or three seasons and 

 includes a study of raAv materials, methods of manufacture, analyses 

 and classifications and physical properties of arsenicals, relative 

 toxicity, amount of arsenic required to Idll insects, and relation of 

 soluble ansenic before being eaten and after being eaten by insects. 

 This Avork has involved a very large amount of detail, requiring the 

 feeding and examination of thousands of insects and careful record- 

 ing of the actions of food. It appears that the percentage of water- 

 soluble arsenic in the arsenicals before they are eaten by insects has 

 little to do with the toxicity of these arsenicals, although with regard 

 to those arsenicals in which the arsenic content is nearly all water- 

 soluble the rate of toxicity is generally highest. As a rule, also, the 

 higher the percentage of arsenic rendered soluble inside the bodies of 

 insects, the higher is the rate of toxicity, and furthermore the more 

 arsenic retained inside of the insects as compared with that voided 

 in the feces, the higher is the rate of toxicity. Evidently onl}' an 

 indefinite opinion concerning the killing power of an arsenical can 

 be inferred from its composition, but judging from both the chemical 

 and insecticidal results obtained the toxicity depends directly upon 



