64 



by the adults. The habits of the protonymphs are similar to those 

 of the larva, and they are very active feeders, while the deutonympha 

 only difier in being able to spin webs. The adult stage during early 

 autumn lasts about 21 days, but the length of this stage depends 

 chiefly upon the temperature and in hibernating forms may extend 

 over six or seven months. The web is frequently used for attachment 

 of the eggs and also serves as a partial protection from natural 

 enemies ; perhaps its most important function is to facilitate travel 

 from one plant to another, and it probably assists in dispersion by 

 high winds. 



With regard to the phenomenon of parthenogenesis in this species 

 two experiments are described, from which it appears that unferti- 

 lised females always produce males, but whether all fertilised eggs 

 produce females is uncertain. The remarkable degree of colour 

 variation in these mites is not considered to be of specific value. The 

 distribution, both geographical [see this i?ewew, Ser. A, iii, p. 13], and 

 according to host, is given in detail with a list of host plants, of which 

 those most infested in the United States are : roses, hops, beans, 

 violets, cotton, strawberry and tomato. The mites will not thrive 

 on : black walnut, nasturtium, radish and wandering jew [Saxifraga 

 sarmentosa]. Some of the more hirsute plants are also protected 

 from their attack. The nature of injury done to the more important 

 plants is described. 



Besides the natural enemies mentioned by Quayle and McGregor 

 [see this Review, Ser. A, i, pp. 143 and 353], the mite Seiiis fomi, 

 Parrott, the Neuroptera, Hemerobius pacificus, Banks, and Chrysopa 

 rufilabris, Burm., and undetermined Syrphid larvae are also recorded. 

 Included as probable enemies are : the mites, Anystis agilis, Banks, 

 Rhyncholophus gracilipes, Banks, the moth Tineola biselliella, Hummd., 

 and the Coccinellids Cycloneda sanguinea, L., Olla abdominalis, Say, 

 and Smilia misella, Lee. 



In taking preventive measures against these mites, useless host 

 plants, especially those that remain green during the winter, should 

 be destroyed. Clean culture is important, and will usually prevent 

 serious infestation. Crop rotation promises good results in certain 

 instances, though care should be exercised in selecting a crop that 

 either matures early before serious mite attacks, or is resistant to 

 them. Trap crops, banding and irrigation are of questionable value. 

 Fumigation is not effective, probably owing to a general resistance 

 of arachnids to poisonous gases, correlated with the difference in their 

 system of respiration. Spraying, while it will kill a large percentage 

 of the mites if properly done, will not give as satisfactory results as 

 with most insects. Nicotine and emulsion sprays are preferable to 

 the sulphur and lime-sulphur sprays. The free use of water as a spray 

 is to be recommended, as it detaches many mites from the leaves and so 

 injures them that they cannot return, besides lowering the temperature 

 and thus reducing the rate of reproduction. It also checks migration 

 and favours the multiplication of predaceous enemies. 



This bulletin, which concludes with a bibliography of over 60 re- 

 ferences, dating from 1761, is one of the most complete works on this 

 pest. 



