December 21, 1906.] 



SCIENCE. 



811 



meneed to emerge by the liundreds. My friend, 

 Mv. Pergande, took the trouble to count the para- 

 sites which actually issued from one Plusia larva, 

 and, to our utter astonishment, the number 

 reached 2,528. An interesting problem now pre- 

 sents itself as to the nature of the cocoon-like cell 

 surrounding each chalcidid pupa in all these dif- 

 ferent hosts from Lithocolletis up to Plusia. In 

 the first place it is no silken cocoon, as is readily 

 shown by the microscopic structure. Neither is 

 it a membrane secreted in the general surface of 

 the chalcidid's body, for but a single wall exists 

 between two adjoining pupae. For the same rea- 

 son it is not the loosened last larval skin of the 

 parasite. But one hypothesis remains, and that 

 is that it is a morbid or adventitious tissue of the 

 host. * * * 



The same phenomenon was referred to by 

 the writer in Insect Life, Vol. IV., p. 193, 

 with illustrations, and again in his paper on 

 the ' Biology of the Hymenopterous Insects 

 of the Family Chalcididse,' in the Proceedings 

 of the U. S. National Museum, Vol. XIV., 

 p. 582 (1892). In the latter paper the state- 

 ment was made that in no case had it been 

 possible to count over 160 eggs in the ovaries 

 of a single Copidosoma, and that the number 

 of parasites issuing from a single Plusia, 

 therefore, was puzzling and only to be ex- 

 plained on the ground that several females 

 oviposited in a single larva at the same time, 

 as all larvae develop together, and transform 

 together, and issue nearly together. 



In the meantime E. Bugnion, in a most in- 

 teresting and important paper entitled ' Re- 

 cherches sur le Developpement Postembryon- 

 naire, 1' Anatomic et les Moeurs de I'Encyrtus 

 fuscicoUis ' (Becueil Zool. Suisse, Vol. V., 

 pp. 435-536, 1891) had studied with care one 

 of these interesting insects parasitic upon a 

 little Tineid larva, Hyponomeuta cognatella, 

 and he found that if one opens the little cater- 

 pillar at the end of April or the first half of 

 May, almost always, or at least with some of 

 -them, the embryos of the Encyrtus (or Copi- 

 dosoma) will be found associated together in 

 -the form of chains or strings. These chains 

 are composed of from 50 to 100 or even 

 120 individuals. The sac which contains 

 the parasites looks like a whitish tube, often 

 hi- or trifurcate, flexuous, folded upon itself. 



floating in the lymph of the caterpillar out- 

 side of the intestine. Formed of a cuticu- 

 lar membrane, it is clothed on the interior 

 with a layer of epithelial-like cells and en- 

 closes a fatty-albuminous mass in which the 

 embryos are enclosed. Later, according to 

 the observations of Bugnion, when the larvse 

 have attained a certain size, say at the end of 

 May or the beginning of June, the string or 

 chain, which may be 3.5 cm. long, presents a 

 series of swellings and constrictions. Each 

 swelling contains an undeveloped larva in the 

 nutritive substance. At the end of June, the 

 parasites having passed their first molt, break 

 the epithelial tube which envelops them, and 

 find themselves free in the body of the cater- 

 pillar. This period (second larval stage) lasts 

 about eight days. Finally the larvse, having 

 cleaned out the interior of the caterpillar, each 

 one pupates by enclosing itself in an ovoid 

 cocoon, and the caterpillar, whose skin molds 

 itself exactly upon these cocoons, becomes only 

 a rigid, bossy mass. The change from the 

 larva to the nymph takes place by a new molt, 

 and about twenty days afterwards the En- 

 cyrtus emerges. 



In 1898 Alfred Giard {Bui. Soc. Ent. 

 France, pp. 127-129) published a note on the 

 development of Litomastix {Copidosoma) 

 truncatellus, a parasite of Plusia gamma, in 

 which he describes precisely the same phe- 

 nomenon previously described by the writer 

 with the same parasite infesting Plusia hras- 

 siccB, but he reared more than three thousand 

 specimens of the parasite from a single cater- 

 pillar. He showed that a single female can 

 lay not more than a hundred eggs and that, 

 therefore, since all of the parasites emerge at 

 the same time, it is almost necessary to sup- 

 pose that several females (twenty-five to 

 thirty) simultaneously attacked the caterpil- 

 lar. This, however, Giard thought was most 

 unlikely, and he believed, therefore, that the 

 phenomenon with Plusia must be explained 

 on the basis of Paul Marchal's preliminary 

 note published the same year. This leads us 

 to Marchal's observations. 



Dr. Paul Marchal, entomologist of the 

 agronomic station under the Ministry of 

 Agriculture at Paris, a naturalist trained in 



