168 INSECT AND VERTEBRATE ENEMIES 



reproduction." It attacks M. domestica in the j^upal stage. The 

 female is a minute insect measuring from 1 nnn. to 2"80 mm. in 

 length and is of a metallic dark brassy-green colour ; the eyes are 

 garnet coloured. The male is about one-third smaller than the 

 female, varying in length from 0'60 mm. to 2'00 mm. It is lighter 

 in colour, more brassy in appearance, metallic and gi-een ; the eyes 

 are sometimes a brilliant carmine. The wings of the male appear 

 to be functionless as they have never been seen to fly and although 

 the female is able to fly both sexes appear to prefer to crawl and 

 are able to crawl quickly. They reproduce very rapidly like most 

 Pteromalid parasites. Maggots and puparia of M. domestica were 

 placed in a breeding jar with females of Nasonia brevicornis on 

 September 9, 1908 ; reproduction of the parasites occurred, and on 

 September 26, 1908, males and females of the Pteromalid parasites 

 emerged. The average life-cycle of Nasonia brevicornis under 

 natural temperatures is 22|- days ; the duration of the develop- 

 ment is longer in the spring than in the summer. The parasite 

 hibernates in the larval stage in the puparium of its host and 

 transforms to a pupa in the spring ; a number of species of Ptero- 

 malids have this habit. 



Another parasite of this group which these authors have found 

 attacking the house-fly is Pachycrepoideus dubius. It was reared 

 in experiments with Nasonia brevicornis and was obtained from 

 the pupae. 



The same authors also describe a third Pteromalid parasite 

 attacking Musca domestica and its coprophagous allies. This 

 species they have named Muscidifurax raptor; it is a minute 

 black insect with clear wings and is somewhat solitary in its 

 habits. The female apparently lays from thirty to forty eggs 

 which are deposited in the pupae, in the interior of which the 

 last annual brood passes the winter as a fuU-gTown larva. The 

 average duration of the summer broods Avas between nineteen and 

 twenty days. 



Richardson (1913) has described a new species, Spalangia 

 muscidarum, which was bred from the pupae of M. domestica and 

 of Stomoxys calcit7'ans\ 



1 More recently Richardson (1913) has described the habits and development of 

 Spalangia muscidarum. The highest proportion of parasitised house-fly puparia 



