252 



PTILOTA: IMAGO EXTERNAL ANATOMY. 



Maxillee, or lower jaws (mx in the figures). These organs 

 are two in number, and are placed beneath the mandibles, 

 from which they differ 

 in their less firm con- 

 sistence and more com- 

 plicated structure, be- 

 ing formed of several 

 parts, and especially l>y 

 the possession of a slen- 

 der articulated appen- 

 dage or palpus, attach- 



ed to each. They ap- 



eat water-beetle (Hydnta J 



hum abore 100, from below 101, 



F'IK. 99, MuilU of the great wter-beetl 

 viftti} Been ' 

 from the back 



pear to be more espe- 

 cially connected with 

 the lower lip, serving, in some instances, as a sheath for its 

 defence ; in the beetles, however, they are generally quite 

 detached. In a table of the comparative variation of the 

 chief insect organs, Mr. MacLeay has shown that the maxilla; 

 are less liable to vary than any other ; hence it is important 

 to note the modifications to which they are subject. 



The maxillae appear typically to consist of five pieces, ex- 

 clusive of the maxillary palpi ; at least, those maxilla* which 

 are the most complicated in their structure exhibit this 

 number of parts. They are the cardo or hinge (figs. }W, K'O, 

 101 a), a most appropriate term, designating a trans vt rse 

 horny piece by which the jaw is affixed within the mouth 

 by membranes. Strauss calls this the branche transversale, 

 Savigny the support, Burmeister the base, and Newman the 

 insertio. This piece is especially distinct in beetles and bees. 

 The two following pieces (b and c) are closely soldered to- 

 gether, and compose the horny pillar between the basal 

 hinge and the terminal lobes. Of these two parts, the ex- 

 ternal portion (c), as first noticed by Latreille, and since 

 named la piece palpiftre by Strauss, and the squama by 



