PLATE I. 



Some mouth-parts of Lachnus longistigtna. 



Figure 1. 

 Cephalic view of the head and ventral view of the labium. 



A. — First two segments of the antenna\ "~ 



B. — Frontal ocellus, situated in the epicranium. 



C. — Compound eye. 



O. — Ocular tubercle. 



D. — Frons. 



E.— Clypeus. 



F. — Basal sclerite of mandibular Beta?. 



G. — Labrum. 



H. — Labium. 



I. — Mandibular setfe separated. 



J. — Maxillary seta; not separated. 



Settv are all slightly displaced for the sake of illustration. 1, 2 and 3 are the 

 first, second and third joints of the labium, respectively. 



Figure 2. 



Ventral view of the labrum. 

 A. — Epipharynx. 



B. — Chitioized rod formed by the approximation of the lateral folds or margins 

 of the labrum. 



FlC4URE 3. 



Dorsal view of a mandibular seta. 



A. — Muscular attachment of seta>. 



B. — The basal sclerite. 



C. ^Greatly enlarged distal point of the same seta or stylet. 



D. — Lumen. 



Figure 4. 



Ventral view of the labium with the seta; removed and the canal open. 



A. — Antelabial sclerite. 



B. — Median chitinized floor which supports the maxillary sette. 

 C. — Chitinized lines which support the mandibular eetie. 



D.^The chitinized floors are in the canal which becomes eliminated at this place 

 on account of the profunal bend in the labium. 



Figure 5. 

 Cross-section of the first joint of the labium with the set;y removed, canal closed. 



A. — Chitin'zed floor. 



B. — Chitinized wall. 



C. — The labial canal in which the seta? may be held. 



D, E. — Paired tongues and grooves, respectively, which firmly lock the two lateral 



edges of the canal together when the insect is drilling into its host-plant. 



This connection is more perfect nearer the distal end of the canal. 

 F. — Outer margin of the labium. 

 G. — Some of the musculature. 



Figure 6. 

 Cross-section of the labial canal with the seta^ in place. 

 A.— Chitioized floor. 

 B. — Chitinized wall. 

 C. — Labial canal. 

 D. — Mandibular stylet. 

 Fi. — Lumen in mandibular stylet. 

 F. — Maxillary stylet. 

 G. — Lumen in the maxillary stylet. 

 H.— Tube through which the food is taken. 



