MEEK : MOUTH-PARTS OF THE HEMIPTERA. 259 



the morphologies advanced by him agree in the main with those 

 held by earlier investigators. 



It will be seen that, in Hemiptera, the Heteroptera have been 

 the subject of most frequent investigation. The Germans, who 

 have done by far the best work along this line, used these forms 

 almost exclusively. For this reason the suborder Homoptera 

 has been selected, and the purpose of this paper will be to give 

 the detailed structure of the homopterous mouth as shown in 

 one of the Cicadidee and to compare it with the buccal struc- 

 tures of the Heteroptera. 



The seventeen-year locust, Cicada septemdecim, on account of 

 its large size and its abundance at certain periods, has been 

 chosen as the type for study. The specimens were collected 

 during their last appearance in this vicinity, May, 1895, by 

 L. L. Dyche, at Lakeview, and by R. G. Gowell, at Linwood. 

 This material was thrown into 95 per cent, alcohol, where it has 

 since remained. The cicadas have been well preserved for ana- 

 tomical study, especially the chitinous and rnuscular sta'uctures. 



TECHNIQUE. 



In order to study the structure of the head, coarse dissections 

 were first made with the needle and knife, and then finer ones 

 with the microtome. The first method, of course, needs no ex- 

 planation, only it may be remarked here that it is an exceed- 

 ingly valuable way to work out the orientation of the parts. 



Great care is necessary in preparing specimens for the micro- 

 tome, and also in staining and mounting the sections. The 

 hard, brittle chitin makes it impossible to secure sections 

 without first softening the chitinous parts. This may be ac- 

 complished by soaking the head from ten to twelve hours in a 

 solution of Eau de Labarraque, consisting of one part Labar- 

 raque to six parts water. With a solution of this strength the 

 muscular structure will be very slightly injured, if at all. 

 From the Labarraque carry the specimen through various 

 grades up into 95 per cent, alcohol. 



For embedding, celloidin-parafiin methods have been used. 

 Celloidin of any desired strength may be made by dissolving 

 the well-dried celloidin in equal parts of ether and absolute 

 alcohol. After the specimens have been properly dehydra- 

 ted they were removed to the 4-per-cent. celloidin solution. 

 Cicada heads were left for at least ten days or even longer. 



