Talponia plummeriana

Talponia plummeriana (Busck)

(Figs. 42–47)

Material examined. NORTH CAROLINA: Wake Co., Morrisville, Lake Crabtree County Park, 6.vi.2019, em. by 19.vii.2019, T.S. Feldman, ex Asimina parviflora, # CSE5675 (2♀, CUIC).

Hosts. Annonaceae: Asimina parviflora (Michx.) Dunal, A. triloba (L.) Dunal (Heinrich 1926).

Biology. Sedlacek et al. (2012) reported larvae boring in unripe and ripe pawpaw (Asimina triloba) fruit, and stated that previously this species had been documented to feed only by boring into pawpaw flowers and peduncles. More recently, larvae have been found feeding in roots and stems. According to Powell & Peterson (2015), this species overwinters in cocoons spun inside the twigs and stems, and in Ohio adults emerge in April or May when pawpaws are in bloom, leaving the pupal exuviae protruding from the stem (apparently always next to a bud). Eggs of the first brood are laid in flowers and the larvae feed on the anthers, then bore into the peduncles and from there into the twigs, feeding on the pith. Oviposition has not been observed in the next generation, but investigations during winter pruning revealed that the frass-filled gallery always leads upward to a leaf scar, beginning as a tiny white hole where a vascular bundle should be. Based on this observation, Powell & Peterson presumed that the egg is laid on the underside of the leaf midrib and the larva bores from here into the twig.

Our specimens were collected on 6 June 2019 as larvae feeding in the leaf midribs of Asimina parviflora, forming galleries that were externally visible as straight or winding brown lines (Figs. 45–47). In some cases the larval entrance hole was not in the midrib but in the adjacent leaf lamina. While we cannot rule out the possibility that some eggs are deposited directly on the midrib as suggested by Powell & Peterson (2015), we believe that the small leaf mines found on A. parviflora at the same locality were made by first-instar larvae of Talponia plummeriana, which then abandoned them to enter the midribs. These mines are full-depth and linear, 2–8 mm long, with granular frass scattered irregularly inside (Figs. 42–44). They are usually initiated adjacent to a major vein and frequently in a vein axil. We first observed vacated mines on 26 June 2018; similar mines were collected in a plastic bag on 5 July, and when the latter leaves were checked in 17 July, a 4 mm, apparently tortricid larva was found in association with window-feeding between the leaves. It was presumed that this larva had emerged from one of the mines, but this is not certain and we were unable to rear it. Fresh mines were found on 2 June 2019, including two that still contained larvae three days later, but these likewise could not be reared to adults. As noted above, we then collected leaves with midrib mines on 6 June. After these leaves turned brown in mid-June it was assumed that this rearing attempt had likewise failed, and they were ignored until mid-July when two dead, moldy adults were discovered. The larvae had fed externally between the deteriorating leaves, window-feeding, skeletonizing, and eating holes. Each constructed a pupal case, reminiscent of those made by Heliozelidae and Incurvariidae, consisting of oval sections excised from two leaves and tied together with silk.