Maskell. — On Aleurodidae. 417 



this stage the differentiation of species can be fairly com- 

 menced. In general form and outHne there is httle distinc- 

 tion, the larvae being (as far as is at present known) always 

 elliptical and flatfish ; but in the colours, in the character of 

 the secretions and fringes, in the arrangement, or the absence 

 of hairs, spines, pustules, or other features, it is possible to 

 note clearly enough the specific differences, as will be seen 

 from the descriptions and figures given in this paper. Gene- 

 rally, in the ea.rliest form of the larva, it is simply a thin, 

 flattish, elliptical, motionless object in which no trace of 

 organs is visible with the exception of an orifice near one 

 extremity, which in this paper I term the " vasiform orifice," 

 and of which I shall speak more particularly presently. As 

 the larva grows, indications of the rostrum appear, and still 

 later rudiments of feet and antennae may be faintly traced. 

 According to the two authors mentioned above, the larva 

 remains in this state only for about a fortnight, and then, 

 without change of position or discarding of its envelope, 

 passes into the pupa stage. This is the view adopted by 

 most writers on the family, and it seems to be, as a general 

 rule, correct ; so that there is extreme difficulty in recognis- 

 ing, except perhaps by size, the difference between a late larva 

 and a pupa, and most authors seem to speak indiscriminately 

 of both, under the names of "early larva," "adult larva," 

 "nymph," &c., these stages being apparently usually dis- 

 tinguished by the more or less definite outlines of the rudi- 

 mentary feet and antennae. In 1889 (Trans. N.Z. Inst., vol. 

 xxii.) I pointed out that in Alenrodcs asplenii, otherwise 

 sufficiently normal as regards tlie question here referred to, 

 it is possible to differentiate the larva from the pupa by 

 reference to the secreted waxy fringes. Still, as a rule, it 

 may, perhaps, be admitted that in this family the typical 

 larva passes nearly imperceptibly into the pupa stage. But 

 I am able in this paper to report some species {e g., A. floccosa, 

 A. piperis, &c.) in which the larva is clearly distinct from the 

 pupa, and in its metamorphosis discards its envelope, the 

 exuviae remaining attached to the pupa-case. In these 

 species I am unable to detect any rudimentary organs in the 

 larva. 



It is possible that at a future time it may be thought 

 necessary to create a new genus, or perhaps a sub-genus, for 

 the species which thus depart from the usual rule. I report in 

 this paper only four of these ; but others may hereafter be 

 found. However, at present I shall not separate them. In 

 only one of the four {A. j^ij^Gris) have I yet seen the adult 

 form, and that does not seem to present any remarkable 

 features. 



The pupa-case, as remarked above, in the normal state 

 27 



