8 



Cincinnati Society of Natural History. 



gella. It is quite probable that Mr. Dimmock is right in regarding 

 them as rudimentary maxilla? and their palpi; but if this is so, still 

 in the other genera above named no traee of their organs has been dis- 

 covered, unless a minute bulb, 1 2000th of an inch long on the neck of 

 the labium in some only of the lower or flat larvae of Lithocolletis 

 represents it. But Mr. Dimmock was influenced somewhat by the fact 

 that in Gracillaria there are two bristles on each side representing the 

 two lobes of the maxillae. In the species of Lithocolletis just referred 

 to, there is only a single little bulb, no bristle, while in Ornix, as 

 shown in the figure, there are three, which perhaps may indicate that 

 instead of maxillae these processes may be the result of a division of 

 thelabrum like that which is found in Tischeria, Antispila, Aspidisca, 

 and JSFepticula, as shown in figs. 58-76. I incline, however, to the belief 

 that Mr. Dimmock is right" in considering them to be the degraded re- 

 mains of the maxillae. 



However this may be, at the first or some subsequent moult, the 

 larvae exchange this rudimentary, or as I have elsewhere called it, 

 "first" form of trophi, for the "second 7 ' or ordinary form in which all of 

 the organs are present. This change takes place at different moults in 

 different genera, or even in different species of the same genus. Thus 

 in Gracillaria, Coriscium alid Ornix it takes place at the first moult; 

 in those species of Lithocolletis, in which the form of the larvae is cyl- 

 indrical (cylindrical group), it takes place at the third moult; in Litho- 

 colletis ornatella, and in the flat group of Lithocolletis, and in the 

 genus Leucanthiza, at the fifth moult, and in the genus Phyllocnistis 

 at the moult (4 ?), at which it passes into the last larval stage. As 

 above stated, in this second or ordinary form, all of the organs of the 

 mouth are present, but in the flat Lithocolletis larvae, and in Phylloc- 

 nistis, some of them are in a very rudimentary or degraded state. In 

 Phyllocnistis this is the case with all of the organs except the spinneret; 

 indeed, I have not been able to detect the mandibles in Phyllocnistis 

 in its last larval stage. Fig. 1 represents the antennae of Phyllocnistis 

 in the "first form," and fig. 2 in the second; fig. 56 the labrum in the 

 first form, fig. 57 in the second; and the labial palpi and maxillae which 

 are absent in the first form are, in the second, rudimentary, as also 

 are the antennae. Fig. 31 represents the mandible of Coriscium in the 

 first form, and that of Phyllocnistis in that form is almost identical; 

 figs. 3 and 4 represent the antennae of a Lithocolletis of the flat 

 group, in the first and second forms respectively ; figs. 5 and 6 

 those of a Lithocolletis of the cylindrical group ; figs. 29 and 30 are 



