18 N. H. Agr. Experiment Station [Bulletin 280 



respraying July 25. Part of this orchard received arsenate of lead 

 sprays. The remaining trees got calcium arsenate. {Hatch Fund) 



Insect Records Enlarged 



The season just closed has witnessed some unusual developments in 

 the insect fauna of New Hampshire. Species of economic importance 

 have appeared in numbers at points farther north than hitherto known. 

 Records have been made of their distribution, economic status, and 

 food plants, and entered in the regularly maintained card index of 

 injurious insects. {Hatch Fund) 



Contact Insecticides 



Two pieces of research on contact insecticides have been completed 

 and published by W. C. O'Kane, J. G. Conklin, L. C. Glover and W. 

 A. Westgate. 



The first of these concerned the reactions of certain insects to small 

 and constant applications of several concentrated chemicals, some of 

 which are especially toxic when applied to sensitive areas on the in- 

 tegument of an insect. A detailed study of the reactions induced by 

 these applications was carried out and the sensitivity of various areas 

 was deteiTnined. The chemicals used included a relatively high con- 

 centration of an extract of pyrethrum flowers, 95 per cent nicotine, 

 cocoanut-oil fatty acid, kerosene, and a so-called white oil. 



The second line of research was concerned with a comparative study 

 of the toxicity of 45 organic compounds, utilizing a technique developed 

 from the research already described, by which small droplets of con- 

 stant size of the pure chemical were applied to definite areas on the 

 surface of the larva of the common meal worm Tenebrio molitor 

 Linnaeus. This study was supplemented by a parallel series of ex- 

 periments in which the same substances were diluted and applied as 

 a spray to plant lice. 



The two reports giAang the results of these two investigations were 

 combined in Technical Bulletin 54, "Studies of Contact Insecticides 

 — VI", entitled "1. Reactions of Certain Insects to Controlled Appli- 

 cations of Various Concentrated Chemicals. 2. A New Technique for 

 Initial Appraisal of Proposed Contact Insecticides." 



Following this the entomologists began a study of the changes 

 brought about in blood cells and in nerve cells of an insect through 

 application of concentrated chemical substances to sensitive areas on 

 the integument. This necessitated the development of a suitable tech- 

 nique in fixing and staining of blood cells and nerve cells. Much time 

 has been spent on this technique, and a suitable procedure has now 

 been worked out. The department is now undertaking detailed histo- 

 logical studies from which it is hoped to derive information as to 

 the manner in which toxic substances bring about the death of an in- 

 sect. 



An additional study now undertaken is concerned with the relative 

 contact performance of a typical so-called "wetting agent" on leaf 

 surfaces and on the surface of an insect. Much confusion exists as 



