Agricultural Research in New Hampshire 53 



To obtain information on the surface molecular layer, the equili- 

 brium angle of contact of water on the epicuticle was determined. The 

 angle was found to be 104.4 degrees, which is within experimental error 

 of the value found for the contact angle of water on paraffin wax (105.5 

 degrees). This would seem to indicate that the outward-directed chem- 

 ical groups on the surface of the epicuticle consist of -CH3 and -CHa 

 groups only, with no oxygen. 



Examination of the exuviae of various insects confirmed the state- 

 ment that steroles are present in this material. Attempts to separate the 

 epicuticular material (cuticulin) from the material of the underlying 

 layers were not completely successful. (W. C. O'Kane, L. C. Glover, 

 J. G. Conklin, A. Standen) 



Technique for Utilization of Houseflies 

 In Studies of Toxicants 



The insect toximeter described in Technical Bulletin 16 has been 

 adapted to utilization of adult houseflies in certain appropriate studies of 

 toxicants. Since the toxic substances obtained from pyrethrum flowers 

 and from derris root are growing scarce, and since both of these have 

 been widely used in fly sprays and cattle sprays, intensive study of pos- 

 sible toxicants from the chemical laboratory are important. A modifi- 

 cation of the insect toximeter makes it possible to use houseflies. The 

 modification involves the use of spheres made of gauze wire. Adult 

 houseflies are introduced into a sphere which is then hung from a suitable 

 support on the turntable of the toximeter. An atomized spray is directed 

 toward the sphere from two angles while it slowly revolves. The flies 

 are immediately transferred from the sphere to an observation cage where 

 the effects of the sprays can be reported. Since the spheres have been 

 made available in large numbers, exploration of possible toxicants can 

 proceed smoothly and rapidly. (W. C. O'Kane, L. C. Glover, J. G. 

 Conklin, A. Standen) 



Sawflies, Gipsy Moths, and Apple Maggots 



The year 1941 was notable for the extreme reduction in infestation 

 of the European spruce sawfly. This reduction was so great as to render 

 further extensive field studies with predators inadvisable for the present. 

 At only one point in the state, in the town of Pittsburgh, was there any 

 evidence of visible feeding by the saw fly. This investigation will be 

 resumed as soon as sufficient infestation develops. 



During the year a number of collections of gypsy moth caterpillars 

 were made in order to obtain data on the prevalence of the introduced 

 larval parasite Farasetigena silvestris, and further collections are planned 

 for the current year. 



In the summer of 1940 observations at a number of points in the 

 state indicated that the gypsy moth parasite, Anastatits disparts, was rather 

 prevalent, and collections of egg masses were made at a number of points 

 to determine the degree of parasitism. Examination of these eggs reveal- 

 ed that in some localities, particularly in the southern counties, as many 

 as 20 to 30 per cent of the eggs were destroyed by this insect. 



