October, '171 BUSCK: MARMARA ELOTELLA 491 



deeply enough to injure the cambium and therefore this species is of 

 Httle economic importance. Mines similar in character, undoubtedly 

 caused by different species, were seen during the summer of 1916 on 

 poplar, ash, and pine. 



Life-History and Description of Life Stages 



Egg. — Description : 



Oviposition took place during the month of August while the writer was away, and 

 hatching had occurred before his return so that only the empty egg shells have been 

 available for examination. Judging from these the eggs are elliptical in shape, 

 flattened below and convex above. Approximate measurements: 0.7 mm. in length. 

 0.5 mm. in width. 



Location on the Tree. — These tinj^ eggs are deposited singly on 

 the smooth bark of apple twigs, oviposition for the most part being 

 upon two-old-year wood, and never on the present season's growth. 

 They are apparently stuck to the bark with a secretion of a mucilag- 

 inous nature. Eggs are rarely laid upon older wood excepting where 

 the bark is thin and smooth. The period of incubation is probably 

 about ten days. 



Mining Larva. — Description of Full-Grown Mining Larva (Fig. 24, 



1): 



Length 5.5-6 mm., width at first and second segment 1 mm. Dorso-ventrally 

 depressed, body strongly constricted behind the second segment, the remaining seg- 

 ments tapering gradually posteriorly and deeply incised laterally at their junction 

 points. Body semi-transparent, lemon-yellow in color and consisting of thirteen 

 segments excluding head. 



Head large, flat, slightly retractile, with dark chitinous supports. Mouthparts 

 very much modified and exserted (Fig. 24, 5). Labrum (Ir) fused with dorsal surface 

 of head and immovable. Mandibles (md) large, flat, and circular saw-like with the 

 distal margin serrated. Labium (li) consisting of a chitinous fold distaUy covered 

 by short spines and extending far back into the head. Maxillae rudimentary, sit- 

 uated in close apposition to the lateral sides of the labium at its junction with the 

 head. Antennae (ant) situated on each side of the head near the mouthparts, con- 

 sisting of two visible segments, the distal one bearing two papillae, one large and one 

 small, two large papillae present on second segment with a small one situated in close 

 proximity to a bristle which extends to the apex of the antenna. Ocelli (oc), two 

 pairs with lenses absent, situated posterior to the antennae. On the lateral margin 

 of the head mid-way between the antennae and the posterior margin of the head is a 

 stout^pine. 



Body. First and second segments widest, approximately 1 mm. Third segment 

 narrower than second and fourth. An internal chitinous shield extends from the 

 posterior border of the head into the prothorax and gives this segment a dark brown- 

 ish color. No legs or prolegs present. Semicircular fold, probably used in pro- 

 pulsion, situated at the posterior extremity. Body without bristles except on first, 

 second and third segments (thorax) where there are two short, stout spines laterally. 

 Anterior fourth of each body segment banded by closely set spine-like protuberances 

 of the body wall. These are directed backward and probably function in bracing 

 the larva during tunneling operations. Spiracles extremely minute but visible with 



