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Simple Summary: The scarce genus of Pelecocera Meigen, 1822 (Diptera: Syrphidae) from the Holarctic Region has 14 species described. The taxonomic diagnosis of the immature stages of Pelecocera has not been performed; however, Pelecocera (Chamaesyrphus) japonica (Shiraki, 1956) larvae were found feeding on Rhizopogon roseolus in Japan. Following the findings in Japan, larvae of Pelecocera were collected in Denmark. We here report the first morphological description of the immature stages of Pelecocera (Chamaesyrphus) lugubris and Pelecocera (Pelecocera) tricincta, as well as specific data on their breeding sites. Larvae of both species were collected feeding on Rhizopogon luteolus in Denmark. The morphology of immature stages of P. lugubris and P. tricincta was studied by using both a scanning electron microscope and a stereomicroscope. A taxonomic diagnosis of the immature stages of Pelecocera and a taxonomic key are provided to separate them from the larvae of other genera. With 14 species, Pelecocera Meigen, 1822 is a scarce and small genus of hoverflies (Diptera: Syrphidae: Rhingiini) from the Holarctic Region. Apart from the finding of larvae of Pelecocera (Chamaesyrphus) japonica (Shiraki, 1956) in fungi in Japan, the larval biology of these hoverflies is virtually unknown. The early stages of all Pelecocera species are undescribed. The adults of Pelecocera (Pelecocera) tricincta Meigen, 1822 and Pelecocera (Chamaesyrphus) lugubris Perris, 1839 are found in Palearctic conifer forests with sand dunes. We here report the first morphological evidence of the immature stages of Pelecocera (P. lugubris and P. tricincta), as well as specific data on their breeding sites. Larvae of both species were collected feeding on the hypogean basidiomycete Rhizopogon luteolus Fr. & Nordholm, 1817 in Denmark in 2021. The first larval stage and second larval stage of P. tricincta, the third larval stage of P. lugubris, the anterior respiratory process, and the posterior respiratory process of the puparia of these two species were analyzed and studied using stereomicroscope and scanning electron microscope techniques. The chaetotaxy of the puparium of each species is also described and illustrated. A taxonomic diagnosis of the larvae of the genus Pelecocera is proposed to separate them from the larvae of other genera of the tribe. [ABSTRACT FROM AUTHOR]