BY FREDERICK A. A. SKUSE. 53 



part in which the female inserts her ovipositor and deposits her 

 eggs. Although many of these excrescences offer a striking 

 analogy to those of the true Hymenopterous gall-flies (Cynipidie), 

 many of the deformations, as, for instance, some to be observed in 

 leaves, are merely discolourations and rolls, while Lasiopteva 

 vastatrix, a native of this country, simply causes a slight swelling 

 of a portion of the skin ; still all the deformations are commonly 

 regarded as galls, however erroneously, and are spoken of as such. 

 Different species are said to attack different plants, or unfrequently 

 an allied species of plant, and each gall-gnat infests only a particular 

 part of the plant, whether it be root, stem, flower or fruit. 



The list given by Julius E. von Bergenstamm and Paul Low 

 (Synopsis Cecidomyidarum, Verh. z-b. Ges. Wien, XXVI, 187G), 

 shows from the variety there recorded, that almost eveiy family of 

 plants probably furnishes sustenance to the larva3 of gall-gnats. In 

 the same highly invaluable paper 463 species of Cecidomyidte are 

 catalogued, being the total then described from all parts of the 

 globe ; probably that number has doubled since then. Out of the 

 463, however, some are not known beyond the larval state, and 

 the deformation they produce ; and altogether, accounts of the 

 economy and larvse of something over a fourth part only have 

 been published. Although the larva of a Cecidomyid is unmis- 

 takable, I do not think that the distinctions between those of 

 different species are sufficient to warrant tlie bestowal of new 

 names, and I much doubt if differences .sometimes existing between 

 the galls or malformations arc very often suflicient criteria, yet of 

 course it is constantly possible to decide that certain remarkable 

 galls are the work of particular insects. Notwithstanding that a 

 considerable amount has Iteen written about this family by 

 eminent men duiing the last 50 years, there is a very great deal 

 yet to bo dom;, and especially outside the more civili/ed portions 

 of the world. 



A few remarks may be added upon the geographical distribution 

 of Cecidomyidie. 



Species of the genus Cecidomyiei have been describixl from 

 almost all parts of the world — in Europe, from Lapland ami 



