354 PROF. S. A. MOKRZECKI. 



nourishment of the plants, owing to an insufficient amount of humus and nitrogen 

 in the soil, aggravated by the entire neglect of manuring by the growers. But 

 the immediate cause of the death of thousands of rose-bushes has proved to be 

 certain galls that are to be found on the stems, reaching 2-3 cm. in length and 

 sometimes twice as thick as the normal stem. 



When the gall is cut open, dark-coloured burrows may be seen circling the stem 

 just under the bark, the number varying from three to fourteen. Up till now, 

 however, no insects have ever been found in these galls, and previous investigators 

 attributed them to Agrilus viridis, L* Injuries of this kind have been also recorded 

 on roses in Italyf and France, | and Houard§ attributes them to the activity 

 of larvae of some Microlepidopteron. 



My investigations have led me to the conclusion that the galls are caused by 

 the larvae of Agrilus fovei coll is, Mars.,|| a species described from Siberia and never 

 recorded previously from any locality in Europe. 



The life-cycle of this new and very destructive pest of roses is not quite clear, 

 but the following points have been actually observed by myself. The beetles appear 

 in the middle of May and live on the leaves of roses, nibbling their margins. The 

 female, after copulation, lays her eggs, up to 30 in number, each separately, under 

 the bark of one-year-old shoots. Each e^^ is laid in a scarcely perceptible oblong 

 hole, made by the ovipositor ; it is about 0-3-0 -4 mm. long, white, with the surface 

 covered with a network of fine furrows. The eggs hatch after 5-7 days, and even 

 during the first 2-3 days of its life the larva may make as many as three annular 

 burrows around the shoot, under the bark, filled with black excrement. No swelling, 

 however, is formed during the first summer (fig. 1). In the second year the swelling 

 is noticeable and increases gradually (figs. 2 and 3), while the infested shoot begins 

 to dry up. In the third year the whole stem gradually dies (fig. 4). 



The life of the larva lasts apparently about one year, and that is why larvae 

 are not to be found in the galls which are already well formed. There may be several 

 galls on the same stem. 



* Dr. Nikoloff, M. Stefanoff and N. Pouchkareff : " The Culture of Roses in Bulgaria," Revue 

 d'Inst. des Recherches agronomiques en Bulgarie, i, nos. 5 & 6, 1921, pp. 11-14 (in Bulgarian). 

 There is a figure of A. viridis, L., and its larva and cocoon, with descriptions taken from 

 Richter von Binnenthal's book: "Die Rosenschadhnge aus dem Tierreiche," Stuttgart (1903), 

 as well as original figures of the burrows as observed by the authors in Bulgaria. 



t Del Guercio, " Intorno ad una deformazione del fusto della Rosa in Italia." — Nuove Relaz. 

 Staz. Entom. Agr. Firenze, pp. 143-146, pi. ix, figs. 1-2. 



X J. Beauderie, " Les Croussins du Rosier." — Hort. Nouv. Lyon, 1911. 



§ " Les Zoocecidies des plantes d'Europe," i, p. 542. 



II Coleopt. Hefte, v, 1869. I am much indebted for the identification of my specimens to 

 the Imperial Bureau of Entomology and to its Director, Dr. G. A. K. Marshall. 



