248 Linnean Society. [June 7? 



tinues to feed until it is full-grown ; which is not until some days, 

 and sometimes even weeks, after the earwig has assumed the imago 

 state. The larva then escapes by forcing itself between the segments 

 of the earwig's body, and the victim,, already rendered sterile, soon 

 dies. The larva at first move& about very quickly, but soon becomes 

 quiet and changes to the pupa condition, usually within a couple 

 of hours. When this state is assumed during- the summer, or in 

 the early part of the autumn, the fly is produced in about a fortnight 

 or three weeks, according to the temperature of the season ; but 

 when the earwig's body is not left until late in the autumn the pupa 

 remains through the winter in the earth, and the fly makes its 

 appearance in the spring ; and this also is the case when the larva 

 remains in the earwig's body during winter, and assumes its pupa 

 condition in the spring or early part of summer. 



The body of the larva is about three-tenths of an inch in length, 

 is soft, white, and tapers anteriorly to a very small but distinct head, 

 which is furnished with a pair of retractile hooks. The body is 

 formed of twelve distinct segments, including the head, and 

 posteriorly has two projecting, corneous, black, tubular breathing 

 organs. The^M^« is oval, smooth, and of a dark brown colour, and 

 retains the breathing organs of the larva projecting obliquely out- 

 wards on either side, at its posterior extremity. The imago fly ap- 

 pears to be referable to the genus Metopia of Meigen, and the author 

 proposes to designate it Metopia Forficulce, and to distinguish it as 

 follows : — 



Genus Metopia, Meig. 



Metopia FoRFicuLiE, cinerea, oculis testaceis, antennis nigris, corpore 

 pedihusque pilis longis nigris vestitis ; thoracis pilis lineas 6 loiigitudi- 

 nales efForniaiitihiis, scutello alarum basi feraoribusque ferrugineis. 



Mused domesiicd aliquanto minor ; Forficulas prope Londlnum infestat.' 



The author also exhibited specimens of another parasite of the 

 same family, Exorista larvarum, which he had bred from pupas of 

 the Emperor Moth, Saturnia Pavonia minor. This species is con- 

 stantly seen in the early part of summer, in the hot sunshine, on 

 hawthorn hedges, when the larvae of Pavonia are feeding. It appears 

 to be the common parasite of the Emperor Moth, in one cocoon of 

 which were the dead pupa of the moth, together with ten living 

 pupae of the fly. In other cocoons there were nine, seven, six, four, 

 three, and two respectively, and in one instance only a single parasite. 

 The pupa of the moth, in each instance, had been perforated by the 

 parasites, wliich thus appear to cft'ect their escape into the cocoon, 



