Molorchus (Caenoptera) minor (Linnaeus, 1758)

Molorchus (Caenoptera) minor (Linnaeus, 1758) View in CoL

( Fig. 2, 3A View Figure 3 )

New continental records. USA: MA: Worcester Co., Worcester , Hope Cemetery, 42.23582°, −71.82453°, 1 Jun 2022, N Keleher, multiple funnel trap, exotic Ips lure (3♂ 1♀, DFOC) ; Same locality, 7 Sep 2022 – 12 May 2023, MJ

Bohne, emergence chamber, ex Picea abies , dead branches, (1♂, DFOC) ; Same locality, 30 May 2023, F Hubacz, multiple funnel trap, exotic Ips lure (1♂, UNHC) .

Diagnosis. Molorchus minor may be distinguished from the sole eastern North American member of the genus by the presence of a narrow, oblique, ivory colored, raised fascia on each elytron ( Fig. 2). Molorchus bimaculatus Say usually have bicolored elytra, but the maculae are not raised, narrow and oblique. The California endemic M. eburneus is very closely related to M. minor , both sharing the oblique raised fasciae, and similar host preferences. They may be distinguished by differences in the shape, setation, and arrangement of calluses of the pronotum as described in the key below. Males of M. minor may be easily distinguished from females by the number of antennal segments (12 in male, 11 in female).

Biology. Duffy (1953) describes the larval biology in detail. A preference for twigs and branches has been observed. Eggs are oviposited in recently cut or damaged branches, and, seldomly, in exposed roots and boles. Galleries are predominantly subcortical and larvae subsequently bore into the outer sapwood where pupation occurs. Adults eclose in late summer but remain in their pupal cells until the following spring. The life cycle is two years.

Hosts. Molorchus minor is polyphagous in conifers and is known to infest Pinus , Picea, Abies , Larix , and Pseudotsuga ( Bense 1995; Bringmann 2001). Reports of larval development in Cupressus and Betula are most likely erroneous ( Vitali 2018). Duffy (1946) reported M. minor in Betula based on his own field observations and breeding experiments. Anisimov and Bezborodov (2021) reported larval development of M. minor in Juglans , Carpinus , Ulmus , Crataegus , and Frangula , however specimen records or references were not provided. It is likely these were taken from the Titan database ( Tavakilian and Chevillotte 2018) which, although listed under larval host, are probably referring to records of adults on flowers of these hardwood genera, or are misidentifications. Sama (1988) concluded that records of M. minor from broadleaf host trees are likely erroneous and should refer to other species. Softwood species records in literature include Picea abies ( Doychev et al. 2009) , Picea pungens Engelm. ( Doychev and Georgiev 2004) , Picea sitchensis (Bong.) Carr. ( Bringmann 2001) , Pinus strobus L. ( Szczepański et al. 2022), Pinus sylvestris L. ( Starzyk et al. 2008), Pinus nigra J.F.Arnold ( Kovács and Hegyessy 1995) , Abies alba Mill. ( Pfeffer and Zumr 1983) , Larix decidua Mill. ( Kovács et al. 2000) and Pseudotsuga menziesii (Mirbel) Franco ( Bringmann 2001) . Additionally, the Titan database ( Tavakilian and Chevillotte 2018) adds the following host species without specimen records or references: Abies cephalonica Loudon , Abies cilicica (Antoine & Kotschy) Carrière , Abies sachalinensis F.Schmidt , Picea jezoensis (Siebold & Zucc.) Carr. , and Picea orientalis (L.) Link. Adults are often found feeding and copulating on flowers of various plants including Crataegus and the family Apiaceae ( Bílý and Mehl 1989) .