. Bee flies of the world: the genera of the family Bombyliidae. Bombyliidae; Parasites. 38 BEE FLIES OP THE WORLD. Text-Figure 2.—Planidial or first-stage larvae of bee flies: a, SysWechus species, after Brooks; b, B. pumilus Meigen; c, B. t/a/pinuj-Wiedemann, after Engel; D, late-stage larva, B. vulpinus Wiedemann; E, Heterosty- lum robustum Osten Sacken, after Bohart. abdominal spiracles anterior to the penultimate ones were poorly developed and possibly vestigial. Sartor described the first-instar larva as highly active and hav- ing a humped appearance in the thoracic region when it is movi
. Bee flies of the world: the genera of the family Bombyliidae. Bombyliidae; Parasites. 38 BEE FLIES OP THE WORLD. Text-Figure 2.—Planidial or first-stage larvae of bee flies: a, SysWechus species, after Brooks; b, B. pumilus Meigen; c, B. t/a/pinuj-Wiedemann, after Engel; D, late-stage larva, B. vulpinus Wiedemann; E, Heterosty- lum robustum Osten Sacken, after Bohart. abdominal spiracles anterior to the penultimate ones were poorly developed and possibly vestigial. Sartor described the first-instar larva as highly active and hav- ing a humped appearance in the thoracic region when it is moving forward. Berg (1940) presented a remarkable morphological study of the larval stages of Systoechus vulgaris Loew; see figures reproduced here. SECOND-INSTAR LARVA Working with Ihnafulus Say, Sartor found that these larvae were 3 mm. long after the first moult, but Marston (1964) found them only to mm. in length at the time of this first moult. Sartor also states that the milky white tissues are much in evidence in this stage, and that 12 body segments are easily counted. The larva is compressed dorsoventrally, with broad pleural protuberances on the third thoracic segment and on the first to fifth abdominal segments; each seg- ment is well marked by segmental lines. He found the head shallowly invaginated wuth only the dark brown mouth hooks discernible. The spiracles were visible on the eighth segment and partly hidden dorsally by the overhanging seventh segment, but project over the ninth segment. The prothoracic spiracle according to Sartor is crescentic and opens posteriorly with 11 barlike sclerotic spots. The caudal spiracle is round with 8 barlike schlerotic spots. Berg (1940) gives an excellent description of this larval stage as well as the first and third stage in his work on Systoechtis vidgaris Loew. Both Sartor and Bohart comment on the difficulty of finding second-instar larvae. Sartor states that the second-instar larvae of Anthrax Ufnatulus
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