403 



abundant were Dakruma larvoe in the District of Columbia in the sea- 

 son of 1879 that it is quite probable the freedom of the Washing- 

 ton maples from this destructive scale since that time has been due in 

 large measure to this Dakruma. Later the insect was found to feed, 

 in a similar manner upon other large scale insects of the subfamily 

 Lecaniiua', and particularly upon the largest of our native species, 

 Lecanium tuUpifer(v Cook, which frequently occurs in enormous num- 

 bers upon the tulip tree and upon different species of Magnolia in the 

 South. 



The Dakruma larva, as is well known, leads a hidden existence. It 

 works beneath the bodies of the scale insects, eating them out, one 

 after another, from below. When the scales are crowded upon a twig 

 or branch, the Dakruma larva j)asses from one to another without show- 

 ing any indication of its presence. Where the scales are more scat- 

 tered, and some little distance intervenes between them, the Dakruma 

 larva still hides itself, traversing the open spaces within a delicate 

 silken tube which it spins as it goes. It is thus protected from ordinary 

 natural enemies, and no parasite has hitherto been known to affect it. 

 It has not, however, escaped the notice of one of the omnii)resent and 

 apparently sharp-eyed chalcidids. There was brought me recently from 

 the insectary a series of little parasites which had been reared, so the 

 labels stated, from a mass of specimens of Lecanium tulipiferw upon a 

 Magnolia tree, A^hich had been sent up from Florida by Mr. Hubbard. 

 The labeler supposed that he had before him a new parasite of the 

 Lecanium. A glance at the specimen, however, showed that the para- 

 site belonged to the subfamily Elachistinai, the species of which are, 

 so far as we know, invariably parasitic upon lepidopterous larvie. An 

 examination of the specimens of Lecanium from which the parasites 

 were supposed to have been reared was immediately made, and they 

 were found, upon lifting them from the twig, to have been eaten out by 

 the larva of the Dakruma, and from the Dakruma larva, not from the 

 scale insects, came the little parasites. 



This observation is of interest, in the first place, as indicating that 

 the Dakruma larva, with all its care, has not succeeded in hiding itself 

 from its natural enemies. In the second place, it emphasizes once more 

 the necessity for the most careful consideration of all the circumstances 

 ill recording the host relations of parasitic insects, and forms perhaps 

 a more striking example of this necessity than any of those mentioned 

 by the writer in an article upon this subject published in Insect Life 

 (vol. IV, pp. 48, 49). In the third place, the observation is of system- 

 atic interest, since the insect reared forms the type of a new genus. Its 

 characterization follows: 



LEUCODESMIA u. gen. 



Female: Resembles Stenomesius Westwood. Abdomen with a distinct, though 

 very short, petiole; scutellum with two longitudinal impressed lines; posterior 

 tibia' Avith one short spur; prothorax subcouical; wings broad. Head broad and 

 well rounded, shrinking very considerably, however, in death. Ocelli forming a 



