Phytomyza catenula, Lonsdale, 2021

Lonsdale, Owen, 2021, Manual of North American Agromyzidae (Diptera, Schizophora), with revision of the fauna of the " Delmarva " states, ZooKeys 1051, pp. 1-481 : 1

Phytomyza catenula sp. nov.

Figs 751-753

Description.

Wing length 1.9 mm (♂). Female unknown. Vein dm-m absent. Eye height divided by gena height: 3.7. First flagellomere ovate, slightly longer than high. Inner margin of fronto-orbital plate not evident, but slightly more sclerotised and raised at and lateral to base of fronto-orbitals. Cheek present.

Chaetotaxy: Two ori (anterior seta 2/3 length); two ors. Four dorsocentrals, decreasing in height anteriorly, with anterior three pairs slightly thinner than posterior pair and more equal in length. Acrostichal setulae in four scattered rows. Intra-alar region with moderate presutural setulae and only two postsutural setulae.

Colouration: Head brown with antenna, first flagellomere, posterior margin of frons, posterior 1/2 of fronto-orbital plate from second ors, back of head, clypeus, palpus and ventral margin of gena dark brown; anterior 1/2 of frons slightly darker; ocellar tubercle very dark, broadly triangular with rounded corners, not touching back of head, leaving postocellars on paler ground. Notum dark brown with moderate brownish silver pruinosity; notopleuron slightly paler. Wing veins brown. Halter white. Calypter margin yellow and hairs light brown. Legs dark brown with apices of femora yellowish.

Genitalia: (Figs 751-753 ) Hypandrium short and thick with broad haired membrane attached to small setose inner lobe. Postgonite emarginate on inner-distal margin and with one seta. Sclerites of basiphallus long and narrow with bases overlapping and interlocking. Sclerite of hypophallus small, pale, flat, separate, in line with basiphallus. Mesophallus and paraphallus not evident. Distiphallus narrow and flat, apically emarginate, dorsally angled and with dark V-shaped sclerotisation; sides with narrow flared lateral wing. Ejaculatory apodeme short, narrow and dark.

Host.

Unknown - likely Caprifoliaceae .

Distribution.

USA: VA.

Etymology.

The specific epithet is Latin for "little chain", referring to this species’ size and type locality.

Type material.

Holotype: USA. VA: Chain Bridge, 14.v.1924, J.R. Malloch (1♂, USNM).

Comments.

Based on the structure of the male terminalia, Phytomyza catenula can be placed within a lineage of morphologically similar Caprifoliaceae -feeding Phytomyza that was revised by Griffiths in 1974 (as Chromatomyia ), with additional species described by Eiseman and Lonsdale (2018) and Eiseman et al. (2021). Within this group, the new species is similar in external and genitalic morphology to three western species that have the apex of the basiphallus exceeding the base of the distiphallus ("supporting sclerite complex" of Griffiths 1974): P. caprifoliae Spencer (AB), P. fricki (Griffiths) (CA, ID, WA, WY) and P. linnaeae (Griffiths) (AB, YT, OR). Phytomyza caprifoliae differs in having the distiphallus evenly thick along its length when viewed in profile, and in ventral view, the distiphallus is smooth laterally, more angulate posterolaterally and distally, and it has a narrower stem on a discrete Y-shaped sclerotisation; furthermore, the hypophallus sclerite is larger, longer, darker and better defined ( Griffiths 1974: figs 26, 27). The latter two species are highly similar, and like the new species, have basal and subapical lobes on the distiphallus laterally, but both also have a better defined hypophallus, the distiphallus is slightly angled distally (not basally), the outline and medial pattern of sclerotisation on the distiphallus differs ( Griffiths 1974: figs 29-32), and P. fricki is slightly smaller.

Figures

Figures 751 - 753. Phytomyza catenula, sp. nov., male genitalia 751 hypandrium and postgonite, ventral 752 hypandrial complex, left lateral, with (functional) anterior view of distiphallus inset 753 phallus, ventral.