78 



The discussion wMcli followed Mr. Kellicott's iiaper related very 

 largely to the preparation of these and similar delicate insects for pres- 

 ervation and study. Mr. Forbes strongly recommended cochineal stain- 

 ing fluid for this purpose. 



The next paper was read by the Secretary, the author being unable 

 to attend. 



THE POSSIBLE AND ACTUAL INFLUENCE OF IRRIGATION ON IN- 

 SECT INJURY IN NEW MEXICO. 



By C. H. Tyler Townsexd. Las Cruces, X. Mex. 



Being situated, as the New Mexico Experiment Station is, in a region 

 where the average rainfall is less than five inches, the question of the in- 

 fluence which irrigation may exert on insect injury becomes with us an 

 important one. The methods of irrigation in practice bere are such as 

 to confine the water wholly to the river valleys, over which it is dis- 

 tributed by a system of acequias, it being impossible on the present 

 plan to conduct the water on to the mesas, which are uniformly dry and 

 barren. Therefore, the actual inflaence which irrigation has on injuri- 

 ous insects in this region does not possess the scope given to the sub- 

 ject in Mr. Howard's able article in Insect Life (vol. ii, pp. 215-222), 

 but is confined to the possible efi'ects upon the various pests which in- 

 fest our orchards, vineyards, ranches, and gardens. 



Certain insects, which spend more or less of their life on or in the 

 ground, are readily affected by this means. On the other hand, many 

 which x)ass most of their existence on trees or high i^lants, are not so 

 easily reached. The most satisfactory way in which to treat the sub- 

 ject will be to consider separately our various pests, especially those 

 which are not amenable to ordinary treatment, taking up the more in- 

 jurious ones first. 



The Tine Leaf-hopper ( Typlilocyha vitifex) may be considered our most 

 injurious insect at the i)resent time. If we consider its amenableness 

 to irrigation, we notice that from the Oigg to the adult it is continually on 

 the upper portions of the plant, except that when newly hatched the 

 young are mostly on the lower leaves, in which the eggs were deposited 

 when these were the only leaves out. It would hardly be possible to 

 raise the water in a vineyard sufficiently to submerge these lower leaves 

 without its breaking out, unless vineyards were surrounded by moder- 

 ately high levees or embankments. Then it would be a question whether 

 such flooding of the vines would not do more injury than do the hop- 

 pers; or whether the young hoppers would not take warning and have 

 time to get on to the higher leaves during the gradual rise of the water. 

 The old hoppers would not be affected seriously unless the water was 

 high enough to nearly cover the vines. It may be thought that turn- 

 ing on the water in the winter would destroy the hibernating hoppers. 



