240 MAINE AGRICULTURAL EXPERIMENT STATION. 1916. 



and two yellow spots at the base besides. Femora yellow; the four 

 anterior ones in some specimens brownish at the extreme base only; 

 the hind pair with a more or less distinct brown ring on the distal half ; 

 four anterior tibiae and tarsi yellow ; the hind tibiae sometimes with a 

 brownish ring, the hind tarsi brownish. 



Male (Fig. 32-44). Front yellow, with a more or less distinct brown 

 spot above each antenna; cross-bands on the abdomen broader than in 

 the female, and distinctly broader than the black interval between them; 

 posteriorly, they are often nearly straight, sometimes distinctly arcuate, 

 especially the third band. The yellow spots on the second segment 

 are not coalescent, but separated by a narrow black interval (in some 

 specimens sub-coalescent) ; the fifth segment is yellow, with a black 

 spot in the middle. The four anterior femora are black at the base; 

 the hind femora are usually black, with a yellow tip; sometimes there 

 is a trace of yellow at the base ; hind tibiae usually with a brown ring 

 in the middle. 



SYRPHUS TORVUS Osten Sacken. 



(See also 30, p. 341 and 35 p. 57.) 



Common to abundant throughout June and first half of July ; 

 rare during late July and throughout August. Reared from 

 among Aphis spiraecola on spiraea and Phorodon humuli on 

 plum seedlings. Hundreds of adults were noted about these 

 colonies, feeding on the honey-dew secreted by the aphids. 

 One male in the collection bears the label: "Hibernating 

 puparium under leaves, Houlton, Maine, May 7, '07." 



Larva (Fig. 33-70, 77, 12, 13). Length, 10 to 12 mm., width 3 to 4 mm., 

 height about 2 mm. Shape sub-cylindrical, tapering rapidly in front 

 to the mouth-parts, slightly narrowed but blunt and emarginate at 

 posterior end; integument raised into numerous transverse folds con- 

 tinued laterally into a distinct longitudinal keel on each side (Fig. 33-70). 

 First three body segments small, retractile, gradually thicker; next 

 eight sub-equal ; terminal segment flattened, bearing on its dorsal sur- 

 face the posterior respiratory process (Fig. 33-70, b; 13}. The spiracles 

 narrow, elongate, nearly straight. The interspiracular ornamentation 

 of slightly elevated, inconspicuous ridges. Circular plate dorso-mediad. 

 Mouth-parts (Fig. 33-77) with a prominent pair of lateral mouth-hooks 

 (c). Between the second and third segments dorsally is a pair of 

 small brownish anterior spiracles (Fig. 33-70 a, n g} ', conical, the semi- 

 circular slit guarded by seven rounded teeth (Fig. 33-7-?). 



The general color of the larvae is brown pink. The integument is 

 tough but transparent; naked but very finely papillose. The black mid- 

 dorsal blood-vessel is prominent and in the living active larvae th<: 

 blood may be seen pulsating regularly from posterior to anterior end. 

 Laterad of this blood-vessel are two long yellowish bundles of fat, 



