The non-parasitic stages vary with season and temperature. The 

 pre-oviposition period varies from 2 to 56 days, the oviposition period 

 from 9 to 122 days. Engorged adults are negatively phototropic. 

 The rate of oviposition varies with the temperature. Engorged adults 

 exposed to temperatures of 24° F. or lower may be killed by freezing. 

 Under dry conditions, they will survive at lower temperatures. 

 Experiment showed that all eggs exposed to a temperature of 2° F. 

 were killed. Within the humid portion of the tick area, humidity 

 is probably not an important factor in larval longevity when the eggs 

 hatch during the same season as they are laid. The average longevity 

 of larvae hatching from overwintering eggs is 94 days, that of larvae 

 from eggs hatching before winter is 176 days. Larvae are able to 

 survive the ordinary winter temperatures of the tick area, except 

 along the northern border. A temperature of 4° F. is fatal to all 

 larvae. 



Chapin (R. M.). Studies on Changes in the Degree of Oxidation of Arsenic 

 in Arsenical Dipping Baths. — U.S. Dept. Agric, Washington, D.C., 

 Bull. no. 259, 13th July 1915, 12 pp., 2 figs., 7 tables. [Received 

 5th October 1915.] 



The changes taking place in the arsenic compounds of dipping fluids 

 are essentially brought about by the growth of micro-organisms, other 

 factors being relatively of little importance. As the result of experi- 

 ments carried out by the author during 1913, the following conclusions 

 were reached :■ — ^(1). No amount of arsenic which can reasonably be 

 used in a dipping bath is sufficient to retard to any appreciable degree 

 the rate of oxidation or of reduction, though a longer time is required 

 for the complete oxidation of a large amount of arsenic than for a 

 .small amount. (2). Under conditions favourable to reduction, the 

 action may progress with extraordinary rapidity, far overbalancing 

 any simultaneous opposing action of oxidising organisms. In such 

 ■cases however the reducing organisms soon exhaust either their vitality 

 or the medium and thereafter are unable successfully to oppose the 

 action of the oxidising organisms. As soon as the dipping fluid is 

 used, oxidising and reducing organisms, together with nutrient matter 

 for either or both of these, are added. Frequent and abundant use 

 of the bath favours reduction ; limited and infrequent use favours 

 oxidation. 



Further experiments upon the effectiveness of certain antiseptics 

 against the activity of the organisms gave the following results : — 

 (1) flotation of a millimetre of paraffin oil on the surface of 

 dipping baths during periods of disuse will measureably retard 

 oxidation by decreasing the rapidity of the diffusion of oxygen into 

 the fluid ; (2) cresylic acid, in admissible amounts, partially inhibits 

 the growth of oxidising organisms, a conclusion borne out by practical 

 experience with proprietary dips containing this substance ; (3) 

 formaldehyde is an effective antiseptic against both classes of organisms 

 and does not interfere with analytical methods for the determination 

 of arsenic. 



The experiments of 1914 were directed to the determination of the 

 practical applicability of formaldehyde as a preservative against 

 (C232) a2 



