INSECTS ON BIRCH: LEAF MINERS

Leaf-mining insects on birches belong to many different insect orders, such as moths (Lepidoptera), sawflies (Hymenoptera), flies (Diptera), and beetles (Coloptera). Below are a few examples from each group, click here, here, or here to get to pages with more birch leaf miners.

Leaf mining moths (Lepidoptera)

Leaf-mining moths on birches belong to over 15 genera in many lepidopteran families.

Eriocrania species

(Lepidoptera: Eriocraniidae)

Several leaf-mining Eriocrania species live on Finnish Betula species. The species can sometimes be separated on the basis of the shape and the location of the start point of the mine. The large blotch mines resemble the mines made by sawfly larvae (see below), but the frass inside the mine is clearly different (thread-like in Eriocrania, granular in sawflies).

 

Mine of Eriocrania sp. on Betula pubescens.

Mine and larva of Eriocrania sp. on Betula pubescens. Note the thread-like frass, which is very different from the grainy frass found in sawfly mines.

 
 

Eriocrania sparrmannella larva inside mine on Betula pubescens. Eriocrania salopiella also starts mining near the center of the leaf, but it occurs earlier in the summer (this young larva was photographed in early July).

Phyllonorycter species

(Lepidoptera: Gracillariidae)

At least four Phyllonorycter species make mines on birch leaves. The mines cause a slight fold on the upper surface of the leaf, while the lover surface remains flat.

 
 

Phyllonorycter ulmifoliella on Betula pubescens. Note the slight folding of the upper leaf surface, which is characteristic of Phyllonorycter mines.

 
 
 

Same P. ulmifoliella mine as above, but seen from below. The lower surface is flat but very thin and finely wrinkled.

P. ulmifoliella larva photographed after removing the thin lower epidermis of the mine.

Stigmella species

(Lepidoptera: Nepticulidae)

Stigmella is a large genus of leaf-ming moths, with numerous species making narrow, winding mines on a wide variety of plants. A thin line of frass in the center of the gallery distinguishes Stigmella mines from those made by agromyzid flies (see below), but separating the six Finnish birch-associated Stigmella species from each other is more difficult.

 

 

Vacated mine of Stigmella lapponica on Betula pubescens.

Stigmella sp. (probably S. confusella) mine on Betula pubescens.

Coleophora species

(Lepidoptera: Coleophoridae)

Coleophora species are known as casebearer moths, which tells the distingushing feature of their larvae: each larva constructs a shelter out of a small leaf fragment, other debris, silk, or frass. The larva then makes a hole on a leaf and feeds inside a mine, while the hind portions of the larva remain inside the case. Each species has its own characteristic way of making the shelter, which can therefore be used as a guide for species determination.

 

Coleophora serratella larva feeding inside mine on Betula pendula. When disturbed, the larva instantly retreats to its shelter, which hangs outside the entry hole on the leaf.

Larval case of Coleophora serratella on Betula sp.

Leaf-mining sawflies (Hymenoptera: Tenthredinidae)

Sawflies from five tenthredinid genera (Heterarthrus, Fenusella, Profenusa, Scolioneura, and Fenusa) make mines on leaves of Finnish birches. Click here to go to the page on leaf-mining sawflies, which also contains links to sites with other leaf miners.

Fenusella nana (left)

(Hymenoptera: Tenthredinidae)

The mine starts from the edge of the leaf, and a characteristic triangular patch of frass usually remains at the location from which the larva started feeding.

 

Profenusa thomsoni (right)

(Hymenoptera: Tenthredinidae)

The mine starts close to the center of the leaf and widens to a blotch mine.

 

Fenusella nana on Betula pubescens.

Profenusa thomsoni on Betula pubescens.

Scolioneura betuleti (left)

and

Scolioneura vicina (right)

(Hymenoptera: Tenthredinidae)

Both of these birch-associated Scolioneura species oviposit on leaf edges, but the blotch mines later encompass a large portion of the leaves. In the case of the S. vicina mine on the far right, the sawfly larva had already left to pupate on the ground, but its cast skin remained inside the mine (visible faintly near the central part of the mine). S. betuleti mines are found in late autumn, the closely related Scolioneura vicina mines birch leaves earlier in the summer.

 

Two mines of Scolioneura betuleti on leaf of Betula pendula.

Scolioneura vicina mine on Betula pendula. Note the grainy frass and cast larval skin.

Leaf-mining beetles (Coleoptera: Curculionidae)

The hyperdiverse beetle family Curculionidae includes a few leaf-mining species. Birch leafminers are found in at least in the genera Orchestes (=Rhynchaenus), Ramphus, and Tachyerges.

Orchestes rusci

(Coleoptera: Curculionidae)

Orchestes rusci mines start at the leaf edge near the tip, and extend towards the leaf base. Before exiting, the larva cuts a circular disc out of the leaf lamina and then pupates on the ground inside the disc. Similar-looking mines are made by other Orchestes species on other deciduous trees.

 

Empty mine of Orchestes rusci in leaf of Betula pubescens.

Leaf-mining flies (Diptera: Agromyzidae)

Agromyzidae is a large dipteran family which includes over 2,500 species worldwide. Agromyzid larvae live inside plant tissues, and many species are leaf miners. Leaf mines made by these flies are often linear galleries that contain only minuscule grains of frass. The larvae are small and have neither legs nor a clearly visible head.

Agromyza alnibetulae

(Diptera: Agromyzidae)

One leaf-mining fly species, Agromyza alnibetulae, occurs on Finnish birches. The fine-grained frass inside the mine is hard to see, which makes it easy to distinguish fly mines from the likewise linear galleries made by Stigmella moths (see above).

 
 

Mine of Agromyza alnibetulae in leaf of Betula pubescens. Note the lack of clearly visible frass.

 

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