J. T. Wadswortii 165 



harder, and the tissue between adjacent chambers that have fused 

 together also becomes drier and harder, and in this manner the hard 

 plurilocular gall is produced (Figs. 3 a and 4). 



The interesting fact revealed during this process is that the stimulus 

 produced by the presence of the larva in the embryonic tissue of the 

 developing ovule, and in the hypertrophied receptacle, induces a reaction 

 of the plant to form a structure that is possibly protective to the plant 

 itself, but which is also at the same time exactly suited to the require- 

 ments of the fully-grown larva, forming as it does a very efficient means 

 of protection to the larva during tlie prolonged period of hibernation. 



Several larvae, pupae, and imagines of Parasia melzneriella Stt. 

 were obtained from the flower-heads during this investigation ; 30 % 

 of the heads examined were found to contain these lepidopterous larvae. 

 By far the greater number of larvae were found in chambers that had 

 originally been made by Urophora larvae, and it is a subject for further 

 investigation to find out what becomes of the original occupants of these 

 chambers. 



Eleven larvae of an unidentified dipteron were found feeding on the 

 ripening seeds ; they were found in 9 per cent, of the heads examined. 

 Small orange-coloured larvae of a Cecidomyid were very abundant, 

 almost every flower-head examined contained several specimens. 



A lepidopterous larva which differed from that of P. melzneriella 

 was found feeding on the seeds in 25 per cent, of the flower-heads 

 collected by Prof. Hickson at St Bees ; as the moth has not yet emerged, 

 I have not been able to identify the species to which it belongs. 



The larvae of two species of Coleophora, C. alcyonipennella Koll. 

 and C. conspicuella 7j. are recorded from Centcmrea nigra. The larvae 

 found at St Bees may belong to one of these two species. 



Sum MAE Y. 



1. A description of Urophora solstitialis L. and an account of its 

 systematic position and geographical distribution are given, together 

 with an abstract of the w^ork of previous observers on this species. 



2. A list of its British and continental food-plants is given ; the 

 records of the latter show that on the continent the larvae feed on 

 various species of thistles, and on three species of Centanrea, but not 

 on Centanrea nigra, whereas with the exception of one record of their 

 occurrence on Serratula tinctoria, the larvae in this country are recorded 

 as feeding exclusively on Centaurea nigra. 



