Feb. is, 1921 Leconte's Saw fly, an Enemy of Young Pines 743 



HEAD (PL. 90, A-E) 



Structural characters. — The dimensions of the head are 2.33 mm. 

 in height (dorsad-ventrad) by 1.75 mm. broad. The capsule (PI. 90, B, C) 

 is of thin chitin with two openings, the occipital foramen in the posterior 

 wall where the head joins the thorax and the buccal foramen in the 

 venter where the pharynx, mandibles, etc., are situated. The head con- 

 sists of the following sclerites, areas, and organs: Epicranium, eyes, 

 antennae, frons, adfrons, pleurostoma, hypostoma, clypeus, labrum, 



and is termed the spiracular area, while the second area, that posterior to the above and armed with few 

 spines, is below folds C l > 2 > 3 and is termed the postspiracular area. 



The sternum consists of two transverse folds before the hypopleurites, one between and one behind 

 them. The hypopleurites bear the uropods. 



These segmental divisions are all rather well defined externally by infoldings of the skin or body wall 

 (PI. 89, B; 91, D, E), which serve to bear the attachments of certain muscles. These muscles are of con- 

 siderable value in defining the folds but are not discussed here in detail, since they would require much 

 comparison of forms, bring matter irrelevant to the subject at hand into the paper, and can better be treated 

 fully in a separate paper after further study. It should be said, however, that the studies made thus far 

 seem to bear out the foregoing conclusions and to offer an excellent method by which to limit segments 

 and segment subdivisions and check up homology of the areas, abdomen to thorax, species to species, and 

 larva to adult. 



The interpretation of the segmental composition and terminology outlined above is applied to the thorax 

 (PI. 91, A, D) in the following way: Each of the three thoracic segments (prothorax, mesothorax, and 

 metathorax) is 4-annulate tergally, and the ann illations when viewed with reference to ornamentation, shape, 

 position, and relation with one another homologize in order with the primary divisions (A, B,C, and D) 

 of the abdomen, the third, C, not being subdivided. 



The pleurum is distinctly divided into four lobes, preepipleurite, postepipleurite, prehypopleurite, and 

 posthypopleurite, in all three segments; and the postspiracular area is present, in approximately its relative 

 abdominal position, in the mesothoracic and metathoracic segments, despite the absence or displacement 

 of the spiracle. 



The sternum consists of three small, rather indistinct folds anterior to the leg's basal attachment to pre- 

 hypopleurite and posthypopleurite. 



Further, the transverse circumference of the larva is divided into longitudinal areas of about equal width, 



(PI. 91. F). 



Tergum or Dorsum 



Thetergum or dorsum in the present paper is intended to designate that portion of the larva which is 

 dorsad of the spiracular and postspiracular areas and which is divided into transverse folds or annulets 

 A, B, C, and D in the thorax, and A, B, C 1 ' 2 - 3 and D in the abdomen. 

 I<*.— Middorsal, a single longitudinal midtergal line. 

 I.— Dorsal, a pair of longitudinal tergal regions, one to either side of the middorsal line. 

 II.— Subdorsal, a pair of longitudinal regions, one to each side of the dorsal regions. 

 III.— Laterodorsal, longitudinal regions, laterad of subdorsal regions. 

 IV. — Supraspiraculai , longitudinal regions, laterad of latero-dorsal regions. 



Pleurum or Latus 



The pleurum or latus designates that portion of the larva between tergum and sternum. 

 V.— Spiracular, longitudinal regions, one to each side of the larva and ventrad of the supraspiracular 

 regions, with the abdominal spiracle situated therein in most sawfly larvae, including Neodiprion 

 lecontei. 

 VI. — Epipleural, longitudinal regions ventrad of spiracular. 

 VII. — Pleural, longitudinal regions ventrad of epipleural. 



VIII.— Hypopleural or lateroventral, paired longitudinal regions, in which are situated the hypopleurites, 

 one to either side of the sternum and ventrad of the pleural regions. 



Sternum or Venter 



The sternum or venter designates that portion of the larva beneath the body between the uropods. The 

 ventrad projection of the uropods places them with reference to the position they occupy in relation to 

 other structures in the adventral longitudinal areas. 



IX.— Adventral, paired longitudinal regions containing the uropods, one protruding from each hypo- 

 pleurite. 

 X. — Ventral, a pair of longitudinal sternal regions. 

 X« — Midventral, a single, midsternal, longitudinal line. 



