378 



A chamber was devised for fumigation under reduced pressure ; a 

 detailed description and figures of which are given. Seeds under a 

 pressure equivalent to some fraction of an inch of mercviry, were 

 exposed to hydrocyanic acid generated within the chamber. The 

 duration of the exposure and the concentration of the acid were varied 

 in order to determine the minimum exposure and concentration which 

 would prove effective. It was also determined whether the seeds 

 would be injured if exposed longer and wdth a higher concentration 

 than that necessary to kill the insects. The results in the table 

 indicate that an exposure of a quarter of an hour was effective if 4 

 grams of sodium cyanide were used ; with a less quantity, the exposure 

 should not be less than half an hour. Fumigation by this method 

 was found to kill insects without injury to the seeds and with a con- 

 siderably shorter exposure than is necessary in the usual method of 

 seed-fumigation. Further experiments are being conducted with special 

 reference to the use of carbon bisulphide. 



Snyder (T. E.). Biology of the Termites of the Eastern United States, 

 '"' with Preventive and Remedial Measures. — U.S. Dept. Agnc.,Bur. 



Entotn., Washington, Bull. no. 94, part ii, 17th February 1915, 



85 pp., 17 plates, 14 figs. 



This is a detailed and elaborate account of North American termites, 

 which are among the most destructive insects to the timber industry 

 in that country. Leucotermes Jiavipes, Kollar, and L. virginicus, 

 Banks, are especially dealt with. The observations are mainly the 

 result of an investigation conducted in 1910 and 1911 as to the character 

 and extent of damage to telegraph poles and mine props by wood- 

 boring insects. Termites of the genus Leucotermes are essentially 

 wood destroyers ; excavations usually follow the grain of the wood, 

 a protective outer layer always being left intact. The burrows of 

 other boring insects are often used as a means of penetrating more 

 rapidly to the heartwood. Although usually confined to moist or 

 decaying timber, dry wood is sometimes attacked. Subterranean 

 passages are also inhabited. After swarming, many sexual adults 

 excavate shallow cells in the earth under decaying wood, and later 

 enter the wood. Infestation usually occurs in this way, rather than 

 by an entrance on an exposed surface. The increase in numbers of a 

 colony is slow, corresponding with the slow rate of egg- laying. The 

 period of maximum egg production is during the warm months — from 

 May to early September in Virginia. In winter, termites retreat to 

 the subterranean passages of the colony ; in spring, when moisture 

 is abundant, nymphs are to be found in the outer galleries, while in 

 summer, there is a migration inwards to escape the dry and hot 

 conditions. The site of the colony is Uable to abandonment if con- 

 ditions become unfavourable. Data on the duration of life are lacking ; 

 workers and soldiers complete their development in one year, while 

 royal individuals probably live at least five years. Swarming occurs 

 7-10 days after the last sexual adults have acquired wings. The 

 eggs hatch in about 10 days ; most of the first brood develop into 

 workers. Young larvae are fed on prepared food and do not eat 

 wood until later in their development. Termites and ants are com- 

 monly found inhabiting the same log ; ordinarily the relations between 



