298 



not a single female having been produced from a virgin female. In 

 the case of Lysiphlebus tritici virgin females occasionally produce a 

 few females in addition to males. 



Investigations at the United States Parasite Laboratory indicate 

 that males are usually produced from virgin females of Braconids 

 and Ichneumonids, but that in the case of Hemiteles, an Ichneumonid 

 hyperparasite, both sexes are produced parthenogenetically. 



Patterson (J. T.). Studies on the Biology of Paracojyidosofnojjsis. 

 IV. The Asexual Larvae. — Biol. Bull. Marine Biol. Lab., Woods 

 Hole, Mass.; Lancaster, Pa., xxxv, no. 6, December 1918, pp. 

 362-371. [Received 20th May 1919.] 



Silvestri reported in 1906 the discovery of a peculiar type of larva 

 in the Chalcid, Lito7nastix truncatellus , Dalm., which he regards as 

 asexual. According to him the egg of Litomastix produces a thousand 

 or more sexual larvae and a variable number of so-called asexual larvae. 

 The former undergo metamorphosis and produce adult insects of both 

 sexes, and the latter, which are characterised by the absence of certain 

 important organs, including the reproductive system, die without 

 undergoing metamorphosis. It has been suggested that these two 

 forms really belong to two very different parasites, as the asexual 

 larvae closely resemble certain very young Ichneumonid larvae. 

 Further, it has been argued that as in many Chalcids larvae of the 

 sexual type are able to break down and assimilate the tissues of 

 their host, it is improbable that a single species should have 

 developed a peculiar sexless and moribund larva for this particular 

 purpose. 



Paracopidosomopsis floridanus, Ashm., which is very similar to 

 L. tninca,tellus, oviposits in the egg of Phytometra {Avtographa) brassicae 

 (cabbage looper), the parasitic egg developing in the body cavity or 

 tissues of the host caterpillar. By the time this is ready for pupation 

 the larval parasites have consumed its entire contents, leaving only the 

 skin of the host. In studying the development of the larvae of 

 P. floridanus only those host caterpillars were used that had been 

 reared under experimental control in the laboratory to ensure their 

 freedom from other parasites. Under these conditions it was found that 

 the parasitic egg produces asexual as well as sexual larvae, irrespective 

 of whether or not the female parent has paired. The time that elapses 

 between the laying of the egg and the emergence of the adults is about 

 28 to 30 days in August and September, and about 40 to 45 in 

 the cooler months of October and November. 



Dissections of a large number of infected caterpillars 12-15 days old, 

 revealed the presence of asexual larvae in nearly every case. It 

 is probable that in a few cases no asexual larvae are developed, and 

 it is difficult to determine the exact number produced by a given 

 egg since they are formed continuously from the 3rd to the 15th day, 

 and those first developed degenerate before the last ones appear. 

 Apparently they do not live more than a very few days after being 

 set free in the body cavity, and seem to perform no function, there 

 being no evidence that they break down the tissues of the host and 

 thus prepare it for assimilation by the sexual larvae. 



