﻿I 68 FIELD AND FOREST. 



Berlin, 1874.) Acariasis is the best known. A very small opening 

 leads to the inner cavity. Seven kinds of galls on ten plants. 



Family II. Anguillula galls. (See A. Braun, Ueber Gallenbildung 

 durch Aelchen, Botanische Zeitiing, 1875, No. 23.) These do not 

 properly belong to the Arthropoden galls. 



Class II. Galls of limited growth. The inhabitants (one or more) 

 remain in the gall only during their larval condition. These galls 

 ripen quickly, usually before the larva have completed their growth. 

 The commencement of the gall is always a group of cells. 



Order I. Larval galls. The larva for a short period of their youth 

 abstract the sap. According to entomologists the egg is always laid 

 on the outside of the plant, but in botanical works the opposite is usu- 

 ally asserted, viz : that the female insect makes a hole with its ovipos- 

 itor and inserts in it the egg. Tachenberg in Forstwirthschaftliche 

 Insectenkunde, 1874, p. 42) says of Cecidomya salieiperda Duf, that 

 the female lays its eggs like a chain on the bark, the larva as they 

 come out bore perpendicularly through the bark into the wood. 



Family I. Mantel (or scale) galls. The insects life is spent on the 

 outside of the epidermis, hence the sap must exude through this to 

 supply the gall tissues proper. In some cases the epidermis is raised 

 on both sides, as in the galls of of Cecidomyia corni and C. ulmarice. 



Group I. Simple galls that are morphologically an extension of leaf 

 tissue. 



Series I. Various kinds of leaf distortion in which the lamina aban- 

 don their natural plane of growth. About twenty-two Cecidomyias 

 are known to produce such malformations, mostly on trees. 



Series II. Spherical leaf galls opening freely to the air, usually near- 

 large nerves. Of these I count about twenty, as Cecidomya annulipes, 

 Hrt. and C. fagi, Hrt. on Beech. C. trcmula, Winn, on Populus 

 tremula, C urticce, Perz., on Urtica dioica, &c. 



Group II. Collective galls. Morphological value is variable. They 

 may be composed of one or more leaves or segments of leaves or of a 

 leafy stem. There are about thirty-five of these, among them C. mill 

 efolii,\j., and C. hyperici, Bremi. 



Series I. In which leaves alone enter into formation of the gall, as 

 the pod like galls of Cecidomyia genista, L., on Genista germanica, 

 and the large flower buds of some Verbascums and Scrophularias at- 



