Linruean Society. 473 



A stream of fresh water, regulated by pipes, could easily be supplied 

 in all districts where the Salmon-tribe abounds. 



Read also " Notes on the Dipterous parasites which attack the 

 common Earwig and the Emperor Moth." By George Newport, 

 Esq., F.R.S., F.L.S. &c. 



After remarking that it is well known to naturalists that many 

 Dipterous insects of the family TachinaricB infest the Lepidoptera, 

 Hymenoptera and Coleoptera, Mr. Newport stated that he has recently 

 found one of the Demiaptera, also the common Earwig, to be subject 

 to the attacks of a species of the same family. He has obtained this 

 parasite, both in its larva and pupa state, from earwigs collected in the 

 autumn in the neighbourhood of London. The earwig is attacked 

 during its larva, or in the earlier period of its pupa state, when the 

 covering of its body is soft and easily perforated. The fly then attaches 

 a single e^s, to some part of its surface, and the young parasite hatched 

 from this penetrates into the abdomen of its victim, and there con- 

 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 moves 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 

 remaiiis 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 pupa 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 Netopia of Meigen, and the author 

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

 follows : — 



Genus Metopia, Meig. 



Mktopia Forficll^, cinerea, oculis testaceis, antcnnis nigris, corpore 

 pedilmsque pilis longis nigris vestitis ; thoracis pilis lineas (j loiigitudi- 

 nales eftbrmautibus, scutello alarum basi femoribusque fernigineis. 



Mused domesticd aliquanto minor ; Forficuias prope Londinuin infestat. 



The author also exhibited specimens of another parasite of the 

 same family, Exorista larvarum. which he had bred from pupae of 

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



