OF THE STATE ENTOMOLOaiST. 93 



of the band, and the two inferior coalesce with the black band margininof it behind. 

 On the eleventh seirment the trapezoidal fuscous spots are of a well-detined oval form ; 

 above the stigma is another similar spot. On the twelfth sejrment the corresponding 

 spots are round, and the trapezoid has its broadest side in front. Tiie anal shield bears 

 two spots centrally and five marofinal ones, of which the medial one is elongated. On 

 the sides of the larva a yellowish shade rests on the incisures. Ventrally, white and 

 black interrupted bandings are observable on the abdominal segments wiien extended ; 

 the thoracic region is almost wholly white; on segments four and tive tlie orange band 

 is continued beneath, inclosing on the former four and on the latter six rounded black 

 spots. The legs are dull yellow, tipped or edged on tiie two joints vvith black, and 

 dotted with black interiorly. The prolegs are dull yellow, with a velvety black base, 

 and with two lateral lines and three bhick .spots (one small); the terminal pair have a 

 black line outwardly and a cluster of black spots behind, wliich, as well as all of the 

 lilack spots noticed "in the above description, are piliferous, having the hair somewhat 

 longer and stouter tlian in (jrata. 



Length of the mature larva one inch and one-eighth ; diameter three-sixteenths of 

 an inch. 



Mr. Lintner then quotes me as writing to him that I find the "two species abso- 

 lutely undistinguishable,'' (my friend has here done me injustice by omitting the qual- 

 ifications, for what I did write was essentially what I- have said above, making reference 

 to the smaller hump and smaller size), and then makes out the following list of differ- 

 ences : 



Contracted by their preservation in alcohol, the two unio larv;e average in length 

 1.05 in. ; the six grata 1.29 in. They differ in form, in that the latter presents much the 

 more prominent hump ou tlie penultimate segment, and is angulated at that point to a 

 degree that were it a vertebrate, it would suggest the idea of its terminal portion drag- 

 ging from having been broken at that point ; in unio the hump is moderate, and the 

 peculiar angulated form, well represented in theflgure, is not seen. 



Unio is the more heavily marked with black, both in its bands and spots. In none 

 of the examples of grata are the black bands broader than one-half the width of the in- 

 tervening white ones, while in one unio their average width is nearly double that of the 

 white. The spots on the head are the same in position in both species, but are smaller 

 in grata. In that species there are usually two distinct piliferous spots on the base of 

 the clypens ; jn two of my examples these are confluent, running together by slender 

 projections in a broad V-form ; in unio the two are united as a band across the clypeus. 

 In unio a black spot, broadly rounded beneath, following the curved line of the ocelli, 

 and tapering to a point above, incloses the four superior ocelli; this is not present in 

 (jrata, but in two examples some of the ocelli are indistinctly annulated with black. 



At c, in Fig. 5, [see 22], the spots on the collar of grata are faithfully represented 

 in position, but their size might have been slightly enlarged. In u7iio, the four spots of 

 the anterior row are separate, but those of the posterior row, from their greater size as 

 (compared with grata., are confluent, except the two medial ones; in grata, these spots 

 are separated by spaces A'arying from one diameter of a spot to two and one-half diame- 

 ters. 



The spots on the caudal hump of grata., shown at d, in the figure, are isolated, 

 while in unio those in each row are connected by the black band to which they are 

 united. 



Similar comparisons might be instituted of all the other spots of the two species, 

 but the above may indicate their differences. The feature which should serve better 

 than any other to" distinguish unio, is the blackisli coloring (its outline not permitting 

 its designation as a stripe), above the prolegs and continued on the two following- seg- 

 ments, the three piliferous spots above the prolegs being connected with it; this is en- 

 tirely wanting in grata. It results, apparently, from the increasing breadth and coales- 

 cence of the black bands as they descend to the ventral region. \n one of the examples, 

 the ventral region of the proleg segments is essentially blackish, which feature was 

 also observed in a number of the living larvae, according to my recollection and that 

 of Mr. Meske. who also collected the larvse and bred from them several imagines. 



The differential features above indicated are not entitled to the reliability that 

 would attach to them, were^they drawn from living examples; but should they prove 

 to be sustained by future observations, there need be no necessity of failing in the de- 

 termination of these species, when eitlier may chance to be collected. 



After all these minutia?, I find no reason to change the opinion I have expressed 

 above, and unless the relative sraallness of the anal hump (and the difference in this 

 respect is not so very striking) prove a constant and reliable criterion, he would be rash 

 who would decide whether a single larva brought to him, without knowledge of its age 



