84 



The maxillary palpi are prominent, but are only one-seg- 

 mented. The labial trunk or proboscis may be described as 

 being made up of three portions, a basal third, the basipro- 

 boscis, from which arise the maxillary palpi, and in which are 

 imbedded two slender chitinous rods, the "maxillary ten- 

 dons" probably representing the greatly reduced rnaxillas ; a 

 middle third, the mediproboscis, strongly chitinized ; and a 

 distal third, the distiproboscis, including the disk-like, fleshy 

 labella. The labella is like that of the horse-fly, but in the 

 house-fly it is the only organ for obtaining food. With it 

 traversed as it is by transverse, horny, chitinous ridges, the 

 " pseudotrachea" hard food substances may be rasped so that 

 fine particles of food mixed with, or sometimes dissolved in, 

 a salivary secretion, which issues from the ridges, can flow 

 into the mouth, along the dorsal furrow of the labial proboscis. 



Make a drawing of the mouth-parts from a lateral view ; 

 and also of a portion of the labella, highly magnified, to 

 show disposition of the pseudotracheas. 



MOUTH-PARTS OF THE MONARCH BUTTERFLY. 



(Anosia plexippus ; order Lepidoptera?) 



In the higher Lepidoptera the mouth-parts have under- 

 gone a profound modification ; mandibles are wholly want- 

 ing and the labium is reduced to a small, immovable sclerite, 

 not functional in food getting. The maxillce, on the other 

 hand, are greatly elongated and are united to form a long, 

 slender, coiling, sucking tube. 



In examining the mouth-parts of Anosia it will be found 

 necessary to remove carefully the scales and scale-hairs 

 which cover the head before bleaching. 



Labrum. Immovably joined to the clypeus is a very 

 narrow, mostly transversal sclerite, the labrum. It bears two 

 tapering, cephalad- projecting points, the pilifers, rising from 



