OF THE MOUTH PARTS OF CERTAIN INSECTS. 187 



head sclerites. Supported upon the caido is tlie stipes or foot-stalk, derivinj^ its mus- 

 cular attachments largely fi-om the cardo ; but to some extent from the head itself, and 

 this feature is a variable one. Surmounting the stipes is a palpifer or palpus-bearer, 

 to which is attached a j^alpus, varying in the number of its joints. This derives all 

 its muscles from the stipes in the typically developed maxilhf. On the inner side of 

 the stipes is attached the subgalea, deriving its muscles from the head in large part ; 

 and this bears a two-jointed galea or hood. It is a matter of some importance to note 

 that this galea is never more than two-jointed under any circumstances, and that the 

 tendency is to maintain that number ; though in many instances it is reduced to one 

 only. It is the most persistent as well as the most variable of the maxillary struc- 

 tures, and is present when any of them exist at all. Inside of the snbgalca, and 

 attached to it as a rule, is the lacinia or blade, which may or may not bear a digitus oi' 

 finger. In the figures just cited we find what may be termed a normal or proportionate 

 development of all the parts, in which no one sclerite is unduly developed or sjjccial- 

 ized. Before attempting to study specializations it is important to note that, when 

 carefully examined, the sclerites are seen to be arranged in three parallel series. That 

 is to say three separable parts have grown together laterally, and this union bears with 

 it the possibility of future di-union or separation for special purposes. AVe have as the 

 inner series lacinia and digitu- ; as the middle, subgalea and galea ; and as the outer 

 the cardo, stipes and palpifer with the attached palpus. Xow if we examine some of 

 the Neuroi^tera, e. g., Sialis (PI. Ill, Fig. IG), we find this lateral arrangement very 

 strongly marked, and it is easily understood that each of these pai-allel sets may have 

 their own peculiar limitations, and that each may be separately and independently 

 modified. 



But lest this seem, after all, a far-fetched conclusion. Ictus examine the niaxilUe 

 of Bittacus strigosvs (PL III, Fig. 4''), and we find almost exactly the hypothetical 

 stale of alfairs actually existing! Lacinia, galea and palpifer all separated, of nearly 

 equal length, but of (piite difierent appearance. The appearance of a tran-versc sec- 

 tion made at about the middle is shown a- Fig. 4:'. For a generalized type this form i- 

 especially valuable, and we may fairly use it as a guide in owv discussion of maxillarj 

 possibilities. 



There is no absolute rule in the matter, but usually the galea tends to become the 

 dominant maxillary organ. In many N'euro[)lera, and e-pecially in their larval stages, 

 the laciniate structure is bu-t marked, as illustrated in IM. Ill, Fig. 9, representing 

 the maxilla of a Perlid larva Here the galea is reduced to a subordinate rank, and in 

 many prcdaceous Coleoptera it is truly palpilbrm. 



In many Orthoplera the development of the galea ju-tilies the name liy fniuiiug 



