Baliosus nervosus (Panzer)

Eiseman, Charles S., 2014, New Host Records and Other Notes on North American Leaf-Mining Chrysomelidae (Coleoptera), The Coleopterists Bulletin 68 (3), pp. 351-359 : 352-353

Baliosus nervosus (Panzer)

Previously, the confirmed larval hosts of this species were Alnus serrulata (Ait.) Willd. (Betulaceae) , Malus sylvestris Mill. (Rosaceae) , Quercus falcata Michx. , Quercus agrifolia Nee , Quercus hemisphaerica Willd. , Quercus nigra L. ( Fagaceae ), and Tilia americana L. ( Tiliaceae ) ( Staines 2006). To this list I add Quercus velutina Lam. (black oak) and Betula lenta L. (black birch, Betulaceae ). I collected mines on Q. velutina on 11 July 2013 and on B. lenta on 12 July 2013, both in Sturbridge, Massachusetts. On 13 July, a birch larva emerged, and on 15 July an oak larva emerged, the latter having a nearly black head and prothoracic plate compared with much paler brown in the former. By 20 July, both had pupated in the bottom of their vials, and I left the pupae there rather than transfer them to jars of soil. The birch beetle emerged on 22 July. On 26 July, I could see with transmitted light that another oak mine now had two adults in it ( Fig. 2 ). By 31 July, the naked pupa and another internal pupa had eclosed. On 2 August in Pelham, Massachusetts, I observed one of two full-grown larvae in a similar black oak mine emerging through a hole it had chewed in the underside—suggesting that pupation outside the mine can occur in nature as well as in laboratory conditions. It is generally believed that all leaf-mining North American Chalepini pupate within their mines ( Staines 2006).

All of the B. nervosus mines I have found begin with a ragged hole through the leaf in the place of any egg remains, as noted for B. californicus above ( Fig. 3 ). Because mines that contained two larvae had only one chewed area, I believe this damage is associated with the oviposition site rather than from the larvae entering new leaves. On 6 June 2014 in Granby, Massachusetts, I found an adult B. nervosus that appeared to be ovipositing at the edge of a similar hole chewed in a black oak leaf. The beetle remained for several minutes despite my manipulating the leaf to photograph it. When it finally left, I was unable to find any evidence of oviposition, but this may be because I had disturbed it. According to West and Lothian (1948), eggs of this species are laid singly or in groups of 2–6 in a pit chewed in the upper leaf surface by the female, usually at least partly covered with a blackish coating of excrement. They found that newly hatched larvae chew directly into the leaf mesophyll from the eggs and are unable to chew through the epidermis if placed on the leaf surface.

On 5 July 2012, I collected a single leaf mine on Castanea dentata (Marshall) Borkh. (Fagaceae) in Pelham, Massachusetts, containing a larva that I am confident was B. nervosus . No other North American hispine is known to have larval hosts in the order Fagales ( Staines 2006) . As with the mines discussed above, this one included a ragged hole and had small, elongate fecal pellets scattered throughout. Unfortunately, the larva died after mining about 2.5 cm 2, and on 21 July a parasitoid ( Eulophidae : Entedoninae ) emerged. The completed black birch mine of a single larva covered about 8 cm 2, and the black oak mine from which I excised two adults covered about 16 cm 2.

Figures

Figs. 1–6. 1) Baliosus californicus mine in Ceanothus velutinus leaf; 2) Leaf mine in black oak (Quercus velutina) with section of upper epidermis removed to reveal two Baliosus nervosus adults and larval frass pattern; 3) Detail of Baliosus nervosus mine in black birch (Betula lenta) leaf, with ragged hole at lower right; 4) Chalepus bicolor larva mining in deertongue grass (Dichanthelium clandestinum), with frass expelled along the leaf margin; 5) Feeding sign of Chalepus walshii adults; 6) Glyphuroplata pluto larva mining in Panicum leaf, with frass in long strands.