NATURAL HISTORY SOCIETY OF GLASGOW. 181 



Of the species affecting the oak, G. cerris, Kollar, is about the 

 same size, and has the antennae also with 12 sessile joints in both 

 sexes; but is markedly distinct, having no dorsal stripes on 

 the thorax, the scutellum not being yellow, and the legs being 

 dusky yellow. 



The larva varies from three-quarters of a line to one line 

 in length, is white when young, but on attaining full growth, 

 ochreous yellow, often bright orange yellow ; body-margins paler. 

 The larvae live gregariously, during summer, among the leaves of 

 slightly arrested and twisted terminal shoots of the oak, Quercus 

 robur, Lin., which they leave to pass their transformations in the 

 earth, spinning each a white cocoon. 



The perfect insect makes its appearance in September. 



The deformation when fresh is not very noticeable, but after 

 the departure of the larvae it withers rapidly, assumes a blasted 

 appearance, and is then very conspicuous. 



Mr Cameron discovered this gall near Cambuslang, and brought 

 me specimens, and he tells me that he has observed similar larvae 

 inhabiting the diseased cup of the acorn. I afterwards found it 

 very abundant in Mugdock Wood, and have also observed the 

 withered shoots in Cadder Wilderness. It would seem, therefore, 

 to be a common and generally distributed species in this district. 



Cecidomyia cerastii, sp. n, 



Male:*" antennae fuscous, 15-jointed, joints stalked. Thorax 

 fuscous, sides at wing-roots testaceous ; dorsum with two rows of 

 hairs, and probably (in life) with three fuscous stripes ; scutellum 

 dusky testaceous. Abdomen dark fusco-testaceous. Legs fuscous. 

 Wings with pale grey pubescence; costa deep fuscous; second 

 longitudinal nervure pale brown, straight, reaching margin before 

 apex of wing ; third, very pale. 



Length, nearly three-quarters of a line. 



The larva, one line long, is brilliant orange or reddish-orange. 

 It is gregarious, and undergoes its transformations within the 

 gall. Two males emerged in the autumn, but escaped my notice 

 until after they were dead. 



The gall is found on Cerastium viscosum, Lin., is terminal, and 

 owing to the internodes not being developed, consists of a cluster 



* Described from dried specimens. 



