Phytomyza ilicis

AGROMYZIDAE
- AGROMYZINAE
- PHYTOMYZINAE

Summary

Species

Phytomyza ilicis Curtis, 1846

Mine

Variable, usually blotch-like but may be entirely linear [with frass in a continuous, slightly off-central line]. Pupariation within the mine.

Host Plants

Ilex

Confusion Species

N/A [the mines of Phytomyza jucunda, a species not recorded from GB&I may be identical]. If the mine is linear, with frass in a slightly off-centre, continuous, dark line, the anterior spiracles must be examined to separate ilicis from jucunda [see January 2021b newsletter].

Recording Grade

2,5

National Status

Common.

Puparium

Orangey-red, slightly flattened.

Adult

Head: frons broad, twice width of eye, not projecting above eye in profile; 2 equal ors, 2 ori (lower weaker); jowls deep, 1/3 height of eye; third antennal segment small, rounded, slightly longer than broad.
Mesonotum: 3+1 dc; acr unusually numerous, in some 6-8 rows.
Wing: 2.8-3.3 mm; second costal section 3.5-4x length of fourth.
Colour: frons somewhat variable, generally brown in front, paler, yellowish above; orbits dark; jowls and face brownish; all antennal segments black, mesonotum matt black; sides of thorax entirely dark; legs black, even fore-knees scarcely paler; squamae grey, margin and fringe black.

Additional information

During 2021, Sam Thomas swept an ilicis-type male which had genitalia that was assumed to be P. jucunda but the phallus was not an exact match. In December 2023, Sam returned to the collecting site and found mines on Ilex aquifolium agreeing with those described and illustrated below. Many mines were collected and adults were successfully reared, with male genitalia agreeing exactly with the specimen collected in 2021.

In November 2023, Dan Houghton found atypical P. ilicis tenanted mines (see images below) on two leaves of a very young Holly sapling in South Hampshire. These mines were collected but out of three larvae, only one survived and pupariated successfully. Examination of the anterior spiracles (see image below) confirm that it is not P. ilicis. Although P. jucunda is the only other species known to utilise Holly in Europe, there are several Nearctic species that also mine Ilex.

Dan found more mines in January 2024 and several were collected for rearing. Adults emerged in late January/early February and examination of the male phallus confirm it is an undescribed species.

This new species will be described in due course but recorders should be aware that mines on Holly fitting the images below must be reared and not assumed to be P. ilicis. Mines of the undescribed species are to be found on seedlings no more than approx. 15 cm in height.