4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



III. DESCRIPTION 



A. ANATOMICAL SECTION 

 I. Material and Methods of Research 



As an object of investigation the blow-fly, Calliphora vomitoria, 

 was chiefly used, the Syrphidae being also studied incidentally. The 

 blow-fly was selected because it is easily procured in large numbers 

 and is of considerable size. Besides, this species appeared as a 

 favorable object because of the very strong development of its 

 skeleton. 



The first investigations were made with an ordinary microscope, 

 but the inadequacy of this apparatus soon became apparent, and 

 later only the binocular was used. The skeleton was studied in 

 preparations in which the soft parts had been removed with liquor 

 potassse. The best results are obtained when the thoracic segments 

 required are left at ordinary temperature about a week in a 50 per 

 cent solution of the alkali. Boiling in the same liquid removes the 

 muscles at once, but this method has the great disadvantage of 

 causing the chitinous parts, chiefly the membranes and ligaments, 

 to shrink. If the preparation appears to be too dark it can be 

 bleached by long immersion in 50 per cent liquor potassse. Rapid 

 bleaching may be attained by means of a mixture of chlorate of 

 potash and a little hydrochloric acid. 



Ordinary Canada balsam preparations of the smaller and thinner 

 parts can be made without any difficulty. The preparations of 

 larger parts, such as median sections of the thorax, were made in 

 the following manner. Small glass dishes with base ground flat 

 were filled with Canada balsam dissolved ^in chloroform, and this 

 was boiled until bubbles ceased to rise. The specimen was cleared 

 up with oil of cloves and then immersed in the balsam while the 

 latter was still warm and soft. It was then properly oriented and 

 protected with a cover-glass. 



Wings, before being placed in the balsam, were boiled in chloro- 

 form according to Walter's method (1907), and thus the tracheae 

 (veins) were freed from air. 



Series of celloidin-sections were prepared both of parts previously 

 treated with liquor potassai and of parts simply hardened in alcohol. 

 From the latter, however, no good sections of the skeleton and the 

 smaller steering muscles could be obtained, because the very brittle 

 chitin, especially in the complicated articular structures, broke be- 

 fore the knife. When the chitin was bleached and softened by 



