56 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 93 



Cape Code area, which is milder, but at times the insect is plentiful 

 over the whole area. One of the best records obtained is the rearing 

 of 139 0. laxifrons from 200 brown-tail moth caterpillars collected 

 at Lunenberg, Mass., in 1915. 



A few specimens in the collection indicate that Oarcelia laxifrons 

 is rarely a parasite of Malacosoma americana and M. disstria. Mr. 

 Webber has corroborated this under laboratory conditions by rearing 

 puparia of Oarcelia laxifrons (European stock) from Malacosoma. 



Records by the writer indicate that Oarcelia laxifrons and Oomp- 

 silura concinnata (Meigen) have been obtained from fie : .d collections 

 from the same host larva, Nygmia phacorrhoea™ In cases of severe 

 competition between these two species, it is considered normally that 

 O. concinnata has the best chance of survival; all conditions being 

 equal, this should occur only when the attack by both iorms on a 

 single individual does not produce a case of excessive multiple super- 

 parasitism. 



Adults, late April to June ; number per host, one to three ; genera- 

 tions, one; hibernation, in the puparium (adult characters usually not 

 formed until the following spring) . 



As the biology of this species has been frequently discussed in 

 literature, only a few additional remarks will be necessary. Under 

 laboratory conditions, crossmating or interbreeding between Oarcelia 

 laxifrons and Oarcelia malacosomae is obtained only with great diffi- 

 culty, and there is probably little or no interbreeding in the field. 



Mr. Webber has completed a series of most interesting laboratory 

 experiments in which Oarcelia laxifrons (European stock) and G. 

 malacosomae have been crossmated. Larvae of the brown-tail moth 

 and both species of Malacosoma have been subjected to attack by both 

 crosses. Adult progeny of these crosses were subsequently secured. 

 It is hoped that the results of this most interesting work and its 

 resultant effect on the taxonomic feature of the two species will be 

 made available in the near future. 



8. CARCELIA SEPARATA (Rondani) 



Exorisla separata Rondani, Dipterologiae Italicae proclronms, vol. 3, pp. 134, 16, 

 1859. — Bezzi and Stein, Katalog der paliiarktischen Dipteren, vol. 3, p. 246, 



1907. 



11 It has been observed in other instances that under equal conditions of competition 

 and host selection, a species of Larvaevoridae capable of superparasitisni can coinhabit the 

 same host specimen along with anotiier species which is also capable of superparasitism. 

 Whereas when a species capable only of solitary parasitism (survival of one specimen) 

 enters into competition to coinhabit the same host specimen with another species capable 

 of either solitary or superparasitism, only one species will survive. Several instances have 

 been noted where Opsosturmia ?iidico1a Townsend (solitary parasite) was the successful 

 survivor in a competition with Compsilura concinnata even though the lar\a of C. concin- 

 nata reached third-stage maturity before it succumbed. 



