SYRPHIDAE OF MAINE. 229 



females were as follows: The length ranged from .8 mm. to 1.057 mm., 

 with an average of .96 mm.; the maximum width ranged from .315 mm. 

 to .4 mm. with an average of .36 mm. Figure 30-7 and 2 is from camera- 

 lucida drawings of three masses of eggs as found in nature. The 

 sculpturing on the egg-shell (Fig. 30-5) consists of irregularly-shaped 

 elevations 5 to 10 times as long as broad and separated by depressed 

 areas several times their width. Each elevation has around its border a 

 varying number (commonly about a dozen) of short, irregularly-sized 

 and un symmetrically-placed, lateral extensions. Forty-five to fifty of 

 these elevations occur end to end the length of the egg, and eighty to 

 ninety side by side around its circumference. Color : chalk white. 



Larva. (Fig. 30-4, 5, 6). Length when well extended 8 to 9 mm,, 

 width about 2.5 mm. Color saturate lettuce-green, a little more yellow- 

 ish mediad. One of the most characteristic things about this species is 

 the unusual transparency of the integument and the unusual plainness' 

 with which much of the viscera shows through the body wall. Integu- 

 ment finely papillose but without vestiture. The isegmental spines con- 

 sist of a fleshy, sub-conical base surmounted by a slender blunt peg of 

 about equal height, the whole small, light-colored, entirely inconspicu- 

 ous. The greenish color is usually entirely obscured mediad, from a little 

 in front of the middle, backward, by a black muss of visceral matter. 

 This mass extends nearly half the total width but is overlaid on each 

 side by several longitudinal chains of whitish, adipose cells, which ex- 

 tend throughout about the posterior two-thirds of the body. Between 

 the latter is a longitudinal, pulsating heart-line, entirely dull black 

 except where it is crossed by folds of the intestine. Laterad of the 

 several whitish chains of cells, and to some extent among them, the 

 black again appears. Near the mid-dorsal line in the second fourth of 

 the body on each side is a single chain of black polygonal cells. The 

 lateral third of the body and all of the anterior end entirely greenish, 

 except for a slender white line on each side formed by the longitudinal 

 tracheal trunks, which run from anterior to posterior spiracles. These 

 trunks give off fine superficial branches mediad at each segment. 



The transverse folds of the integument and the division into somites 

 are inconspicuous, as are also the antennae and anterior spiracles. The 

 latter are a little more than usually elongate and conical. The double 

 A-shaped mouth-parts may be seen through the segments at the anterior 

 end or terminally when extended. There is a pair of heavy, black, 

 lateral mouth-hooks. Just in front of the posterior respiratory organ, 

 between the two tracheal trunks, is a mass of very finely-divided white 

 filaments (tracheae?) especially noticeable when the larval skin is moist. 



The posterior respiratory process is about .3 mm. broad at the end, 

 about .17 mm. in depth, and elevated above the surface of the last seg- 

 ment only to a length of about .1 mm. or .12 mm. Circular plate evi- 

 dent; the three pairs of spiracles unusually short, less than twice as 

 long as broad, .05 mm. long by about .03 mm. wide. The inter- 

 spiracular ornamentation consists only of four pairs of short, rounded 

 nodules. A moderate emargination between the two stigmal plates. 



