OF THE MOUTH PARTS OF CERTAIN JNSECTS. 177 



get at the steps by which the present " beak " was developed, and my material is not 

 sufficient foi- that purpose. The mandibulate type, on the contrary, proved well 

 adapted for variation, and its differences and modifications are here traced. 



For convenience, Kolbe's figures of the mouth parts of a gTasshoi)i)er are repro- 

 duced on PL IIT, Fig. 22, and may be i-eferred to in connection with the following 

 explanation. 



In a well-developed mandibulate mouth we have, forming an upper lip, the lab- 

 rum, often notched in front or toothed ; but never a paired organ, never with appen- 

 dages, and never mechanical in function. It is articulated at base to the clypeus and 

 serves to shield or protect the mouth in front; as a matter of fact, not a functional 

 mouth structure at all. It is marked Ihr in all figures. 



More or less intimately associated Avith it on the inner side is the epipharynx, which 

 is compared in function witii the palate of vertebrates, and is furnished with sensory 

 hairs, pegs or pittings. It may be so closely united with the labrum as to form, i)rac- 

 tically, a part of it, or may be entirely free. If free from the labrum, the epipharynx 

 is more closely united with the other mouth parts, and in such cases its supports go to 

 the mentum or labial structures. Not infrequently it has attachments to both. In 

 foi-m it may be a mere pointed process, or it may be a more or less divided, plate-like 

 organ; but its functions are gustatory or sensory in all cases — it never becomes a 

 functional mechanical structure, and I have never found it without a more or less de- 

 veloiJcd labrum to shield it. It is lettered epi in all figures. 



Just below these covering and gustatorj^ organs is a paii* of mechanical structures 

 — the mandibles — set, one on each side of the head, and attached to the inferior margin 

 of the epicraniuni or an extension from it. These mandibles are never jointed, rarely 

 bear appendages, and never such as are functional, rarely have a movable tooth, and 

 are usually solid and highly chitinized. They are actualh' made up of a number of 

 sclerites, laterally united, but distinguishable hi ceilain types like Cojjris, PI. I, Fig. 8. 

 I have elsewhei'c named and homologized these sclerites ; but as the matter is not in 

 dis})utc, and of no importance here, a simple reference to the figure in which they arc 

 named is all that is necessary. The position of this pair of mouth structures is iuva- 

 riable. fhcy are completely disassociated from the maxillary or labial structures and 

 remain attached to the head wlicii all the othei- parts are i-emoved in a body. They 

 attach b}^ socket joints to the epicraniuni and their tendons and muscles attach to 

 its inner surface. They never change in function, never become united with or 

 attached to the other mouth ortrans and never become internal structures. When not 

 needed for chewing or biting the tendency is to obsolescence: never toward a change 

 into a thrusting or piercing organ, so far as my observations extend. 



