HEAD, MOUTH-PARTS, ORTHOPTERA EUPLEXOPTERA 253 



MATERIAL AND METHODS 



In order to make the study as comprehensive and representa- 

 tive as possible, the following species have been selected and 

 examined: Blatta orientalis (Blattidae), Mantis religiosa (Man- 

 tidae), Diapheromera femorata (Phasmidae), Gryllus pennsyl- 

 vanicus (Gryllidae), Orchelimum vulgare (Locustidae) , Steno- 

 pelmatus sp. (Locustidae), Melanoplus differentialis (Acrididae), 

 Tettix arenosus (Acrididae), and Anisolabis maritima (Euplex- 

 optera) . 



The specimens were treated, as a rule, with a 5 per cent solu- 

 tion of potassium hydroxid from five to twenty-four or more 

 hours (depending upon the degree of chitinization of the struc- 

 tures) and examined in 70 per cent alcohol under a binocular 

 microscope. The drawings were made free hand after measuring 

 the dimensions of the specimens by means of an ocular microm- 

 eter. 



OBSERVATIONS 



A. Fixed parts of the head 



The conditions in the cockroach have been taken as typical, 

 and those of other families have been discussed only where they 

 differ from this type. Detailed descriptions have been omitted; 

 with the accompanying figures it is believed that no difficulty 

 will be experienced in identifying on specimens the structures 

 shown. In order to avoid confusion, the skeleton of the head and 

 its appendages have been described in every case as if the mouth 

 were directed cephalad. 



The epicranial suture in Blatta (fig. 1) is the inverted Y-shaped 

 median suture. The stem (es) of the Y begins at the occipital 

 foramen, extends cephalad on to the dorsal aspect for some dis- 

 tance, then bifurcates. Each arm (ea) extends obliquely toward 

 an antacoria and terminates in the whitish area mesocaudad of 

 the latter. The epicranial suture is well developed in Gryllus 

 (fig. 5) and Anisolabis (fig. 12) ; in the former, however, the cau- 

 dal portion of the stem is obsolete in untreated specimens, and 

 the arms are short and terminate at the mesal margins of the 



