Beiträge zur Biologie und Ökologie der Fichtengallmücke Dasyneura abietiperda Hensch. (Cecid. Dipt.)¹

Abstract

Zusammenfassung Die Gallmücke Dasyneura abietiperda Hensch. tritt in einigen Revieren Schleswig‐Holsteins an Fichtenmaitrieben auf. Ihre Biologie und der Bau der Galle werden beschrieben. Die Generation ist einjährig, die Imago fliegt im Mai, die Larve ist im Herbst ausgewachsen und überwintert in der Galle, deren Entwicklung von der Larve abhängig ist. Ein Vergleich mit der zweiten bisher auf Fichtentrieben gefundenen Gallmücke Dasyneura piceae Hensch. zeigt weitgehende Übereinstimmung in Morphologie der Jugendstadien, Biologie und Gallbildung. Es wird vermutet, daß es sich bei dieser zweiten Art um eine abweichende Form von D. abietiperda oder aber um eine inquiline oder parasitische Art handelt. Wirtspflanze war ausschließlich die Rotfichte (P. abies). Es waren alle Altersstufen zwischen sieben Jahren und Hiebreife befallen. Der Schaden besteht in einer Verformung der Krone und kann stellenweise erheblich sein. Die natürliche Sterblichkeit ist im ersten Larvenstadium sehr hoch. Als wirksamer natürlicher Feind tritt eine Chalcididenart auf. Eine chemische Bekämpfung erscheint nur in Sonderfällen notwendig. Summary The gall midge Dasyneura abietiperda Hensch. occurs in some districts in Schleswig‐Holstein in young spruce shoots. Its biology and the structure of the gall are described. There is one generation annually, the adult flies in May, the larva is mature in autumn and hibernates in the gall, the development of which is dependent on the larva. The morphology of the larva, the biology and gall formation is very similar to that of the second gall midge found in spruce shoots, Dasyneura piceae Hensch. and it is assumed that this second species represents an abnormal form of D. abietiperda or an inquiline or parasitic species. The host was exclusively the red‐spruce (P. abies) which was attacked at any age between 7 years and the time it was ready for felling. The damage consists of a deformation of the crown and can be considerable in places. Natural mortality is very high in the first larval instar, a Chalcid species is an effective natural enemy. Chemical control appears to be necessary only in exceptional cases.

Piceacecis (Diptera: Cecidomyiidae), a New Genus for a Non-Native Pest of Norway Spruce from Europe and its North American Relative

“…We concur with Schneider (1962), who determined by regular observations throughout the season that there is one generation per year. Earlier publications had postulated two generations per year (Barnes 1951).…”

“…Dasineura abietiperda was initially described as appearing in blister galls along the length of twisted branches that had lost their needles; D. piceae (Henschel) was described for the blister galls that in aggregate cause the base of the branches to swell. Inasmuch as we reared indistinguishable adults from both kinds of damage and no second generation was observed by us or by Schneider (1962), we consider the symptoms to be caused by the same insect.…”

“…The heaviest number of galls typically occurs under bud scales . In Germany larvae pupated in early to mid-April and adult emergence followed in about two weeks in late April to early May (Schneider 1962). Schneider (1962) found that eggs were laid between scaly leaves of buds or near needles of young shoots and that larvae hatched in about one week and bored into shoot tissue.…”

“…) and several hours spent by one of us (LG) looking for the damage near Düsseldorf, Germany, uncovered none. The insect's biology and ecology in northwestern Germany were studied by Schneider (1962), but the species has never been properly described, nor has its taxonomic position been critically appraised. The American species, P. tsugae, and its new junior synonym, P. piceae Felt, have also never been properly described or satisfactorily placed to genus.…”

“…The life history of D. abietiperda was studied in Germany by Schneider (1962) and of P. tsugae (as P. piceae) by Smith (1952) in New Brunswick, Canada. Both species have a similar life cycle consisting of one generation per year with the larval stage overwintering; however, emergence of P. tsugae adults was later than D. abietiperda, presumably because New Brunswick, Canada, is generally colder than Germany.…”