Petiole miner/borer (Diptera: Agromyzidae) in Arnoglossum

Record Details

Record no.:	0686
Feeding guild:	Petiole miner/borer
Taxonomy:	Diptera: Agromyzidae: cf. Melanagromyza sp.
Stages observed:	trace, puparium
Hosts in Arnoglossum:	A. reniforme (great indian-plantain)

straw-colored, cylindrical puparium nestled in narrow, shadowy tunnel with rough walls — Puparium from *A. reniforme* petiole

Tunnels of this agromyzid occur in basal leaf petioles of the host. In one example observed, the tunnel system wound through much of the length of the petiole and even extended into some of the major veins of the leaf. The tunnel walls showed a ragged texture.

In 2021 I found several puparia in petioles, usually one or two per petiole. In 2023 I found tunneling in the lower portion of a petiole that appeared to be agromyzid in origin, and in 2025 I found a single additional puparium in a petiole.

In the 2021 findings I observed the placement of the puparia within the petioles. In each case the puparium was formed in a tunnel that led from the petiole interior to the surface tissues, with the puparium positioned just behind a roughly circular, transparent operculum of petiole epidermis that sealed off the end of the tunnel from the outside world.

One of the 2021 puparia whose characteristics I recorded was straw-colored with brownish posterior spiracular plates without obvious horns. Interestingly, the spiracular plates were borne on short lobes that were subtly but noticeably different in color from the surrounding surface of the puparium, and the anterior spiracles were unusually large and perhaps even more prominent than the posterior spiracles, both somewhat unusual features among stem borer agromyzids I have examined in this study. Furthermore, the arrangement of the posterior spiracles and the prominence of the anterior spiracles in the 2021 puparium appeared to match the same features in the 2025 puparium. These characteristics are significantly different from those shown by the puparium of M. arnoglossi (record 0075, 0078, so I suggest the petiole tunneler is a different species.

I have not yet reared adults, but they apparently emerge in spring from overwintered puparia.

Featured Images

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broadly triangular leaf blade with thick petiole about half again as long as the leaf blade is wide — Image #: 686-01 Inhabited basal leaf of *A. reniforme*. (Photo date: October 4, 2021)

there is a faint yellow subsurface trail visible in the otherwise greenish-yellow petiole surface — Image #: 686-02 Tunnel in petiole, viewed from the exterior. (Photo date: October 4, 2021)

the smooth and unremarkable exterior surface of the petiole is punctuated by a transparent window of epidermis covering the terminus of the fly's tunnel — Image #: 686-03 Operculum at end of exit tunnel in petiole. (Photo date: October 4, 2021)

the operculum is about one third as wide as the petiole is thick — Image #: 686-04 A second example of an operculum in an inhabited petiole.

brown, disc-shaped spiracle plates are at the ends of cylindrical lobes that are about as tall as wide — Image #: 686-06 Posterior spiracles of puparium from previous photo (0686-05).

the tunnels are whitish with ragged scraps of plant tissue hanging from the tunnel walls — Image #: 686-07 Tunneling in basal leaf petiole.

the affected part of the vein is subtly yellower than the unaffected part — Image #: 686-08 Base of leaf blade with petiole tunnel (hidden under the intact epidermis) extending up into vein. The larva stopped penetrating into the vein at the location denoted by the arrow; note the discoloration of the tunneled area relative to the unaffected vein tissue.

the affected part of the vein is more clearly discolored in this view, with the contrast between the healthy and damaged portions being more obvious, and the epidermis of the affected part of the vein has collapsed and wrinkled slightly — Image #: 686-09 Closer view of the affected vein in the leaf blade.

the tunnel takes up most or all of the width of the vein and has whitish ragged walls — Image #: 686-10 Same view as previous photo (686-09), but with the epidermis of the vein partly peeled away, revealing the tunnel beneath.

the dangling filaments of shredded vein tissue hanging from the tunnel walls are wispy and up to four or five times as long as wide — Image #: 686-11 Closer view of tunnel in leaf vein.

the strip of epidermis peeled away to expose the tunnel also has filaments of shredded tissue dangling from its inner surface, revealing that the larva's tunneling in the vein was shallow — Image #: 686-12 Another view of the tunnel in the vein.

the whitish shredded bits on the tunnel walls contrast sharply with the green color of healthy vein tissue in this view, and most of the long narrow portion of the vein gently arching across the frame has been tunneled — Image #: 686-13 Tunnel in leaf vein.

the squat, cylindrical puparium's rich gold color stands out against the pinkish color of the petiole tissue — Image #: 686-14 A tunneled petiole, dissected in the field, revealing intact puparium inside. (Photo date: November 13, 2025)

the puparium is nestled in a tunnel in the succulent petiole tissue; the tunnel has brownish walls, and the posterior spiracles of the puparium, borne on short lobes, are evident along with the prominent, short but slender anterior spiracles — Image #: 686-15 Closer view of puparium from previous photo (686-14), with another angle in the inset.

Page created: February 10, 2026. Last update: February 11, 2026