THE SYRPHIDAE OF OHIO 55 



Syrphus americanus Weidemann 

 (Plate IV, Figs. 41-57.) 

 See the O/iio N'atiiral/st, Vol. XII, No. 5, pp. 477-488, March, 1912. 



Egg — L/englh about 0.9 mm., diameter about 0.3 mm., white. Taken on apple, 

 Phragiiiifes, black willow and Riuiiex sp.. May, June and July, 35 to 45 eggs depos- 

 ited by each female in captivity. Duration in egg stage, indoors, 55 to 60 hours. 



Larva — When first hatched, very hairy in appearance. When mature, about ii 

 mm. long, slender, prominently wrinkled. General color yellowish or salmon-brown 

 marked with black and white or yellowish-while. Inte^.'ument covered with short, 

 close-set black spines, almost microscopic. Segmental bristles not conspicuous. Pos- 

 terior breathing appendage short (0.2 to 0.25 mm. in length) and about twice as broad, 

 emarginale for half its length; dorsal spiracular spines moderately long, sharply con- 

 ical witha very small, lateral, sub-basal spur. The spiracles irregularly and consid- 

 erably curved, about 0.25 mm. long, the median one 011 each side nearer to the ven- 

 tral than to the dorsal one. Mouth parts with three pairs of booklets, the jaws rather 

 short;. 



Larvae were taken on cabbage and other Cniciferae, feeding on Aphis brassicae, 

 in colonies of aphids on Phraginites, preying on the European Grain Aphid (Sip/io- 

 coryne avenae) on apple, on Aphis niiiiieis on Riiiiiex spp., and among colonies of 

 Melanoxanthiis salitti on black willow. 



Puparium — Length about 6.5 mm., height 2.5 mm., width 2.6 mm., not strongly 

 elevated posteriorly. Integumental spines rather prominent, color brownish. Dur- 

 ation in pupal stage (indoors) 48 hours to 8 days. 



Adult — Length 8-10 mm. Face with brown stripe in middle not reaching anten- 

 nae. Cheeks blackish, separated from mouth by a narrow yellow border. The 

 yellow a>)dominal bands separated from the margin by a narrow black interval. 



Syrphus sp. — The larvae described below were, when taken, supposed 

 to be, without doubt, distinct from the others I had reared. But when the 

 adults emerged they were found to come within the limits of Syrphus 

 americanus Weidemanu as described by Osten vSacken. It has not been 

 possible up to the present time to determine whether both kinds of larvae 

 and ptipae can be secured experimentally from the same strain; nor have 

 I been able to find a satisfactory basis for the specific separation of the 

 adults although they appear on the whole somewhat distinct from the 

 ones I have reared from Aphis brassicae, etc., as described under the pre- 

 ceding species. The following descriptions and notes are therefore given 

 on what may prove to be a distinct species, showing possible convergence 

 of imaginal characters toward S. americanus; or else an interesting and 

 rather striking larval variety of the former species. 



Larva— Length 1 1 to 20 mm., width 2.75 to 5 mm., height 2.5 to 3.5 mm. The larg- 

 est and most beautiful of the Syrphidae that I have seen. The shape and appendages 

 are suggestive of .V. americanus: a long, comparatively slender larva tapering nicely 

 in front, with the entire dorsum beset with short microscopic hairs. These integu- 

 mental hairs seem somewhat smaller than those in S. aineiicanus and also rather 



Syrp. 5 



