BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [118] 



can be secured under screens or covers out of doors for the winter in 

 slieltered situations. Many species which, if kept in a warm room 

 can not be reared, will, if subjected to freezing weather under slight 

 protection in the open air, emerge successfidly the following spring. 



The greatest care is necessary in the breeding of Tenthrediuidte, as 

 most of them transform under ground and are single brooded, the larvae 

 remaining in the ground from midsummer until the following spring. 

 Nothing but constant care in maintaining uniform moisture and tem- 

 perature of the soil will insure the success of such breeding. Some 

 ST)ecies bore into rotten wood or the stems of plants to undergo their 

 transformations, as for instance the Dogwood Saw-fly {Harpiphorus 

 varianus). This species, unless sujDpUed with soft or rotten wood in 

 which to bore, will wander ceaselessly round the cage, and in most 

 cases eventually perish. 



Where a small room can be devoted to the purpose, an excellent 

 wholesale method of obtaining wood-boring insects {CoUoptera, Lepi- 

 doptera, etc.) is to collect large quantities of dead or dying wood of all 

 sorts or any that indicates the presence of the early states of insects, 

 and store it in such apartment. The following spring and summer the 

 escaping insects will be attracted to the windows and may be easily 

 secured. The objection to this method is that, in many cases, it will be 

 impossible to aetermine the food-habit of the insect secured, owing to 

 the variety of material brought together. 



The Root Cage. — For the study of insects which aft'ect the roots of 

 plants a root cage has been devised by Prof. J. H. Comstock which is of 

 sufQcient importance to warrant full description. It consists of a zinc 

 frame (Fig. 125a) holding two plates of glass in a vertical position and only 

 a short distance apart, the space between the plates being filled with 

 soil in which seeds are planted or small plants set. Outside of each glass 

 is a piece of zinc or sheet iron (b) which slips into grooves and which can be 

 easily removed. When these zincs are in place the soil is kept dark. ^ 



The idea of the cages is, that the space between the glasses being 

 very narrow, a large part of the roots will ramify close to the surface of 

 the glass, so that by removing the zinc slides the roots may be easily 

 seen, and any root-inhabiting insects which it may be desirable to breed 

 may thus be studied in their natural conditions without disturbing them. 

 Prof. Comstock has used this cage very successfully in studying the 

 habits of wire-worms, and its availability for many of the underground 

 insects, such as the Cicadas, root-lice, larvse, etc., is apparent. These 

 frames may be made of various sizes, to accommodate particular insects. 

 It will be of advantage in many cases, in order to secure the natural con- 

 ditions as nearly as possible, to sink the cage in the soil, and for this j)ur- 

 pose Prof. Comstock has had constructed a pit lined with brick for the 

 reception of his cages, and employs a small portable crane to lift them 

 out of the ground when it is desirable to examine them. 



