■October 1S91] 



PSTCHE. 



163 



influence them before hatching. More- 

 over, they differ in another important 

 particular, which has not so far been 

 recorded, namely, in the number of lar- 

 val stages. Harrlsii has seven stages, 

 with a width of head at maturity of 3.3- 

 3.6 mm., while tessellarlshas nine stages 

 and a width of head of 4.1-4.3 mm. 

 These measurements were derived from 

 a number of larvae I'aised in confinement, 

 as well as from some found in nature, 

 and correspond, varying only within the 

 limits indicated. 



I have not been able to find any dif- 

 ference in the markings of the imagos 

 bred from these two forms of larvae, 

 but an examination of the male genitalia 

 reveals differences that appear to be 

 constant. In harrisii, the side pieces 

 are furnished on the lower side with two 

 tapering, overlapping points, the lower 

 one longer than, and projecting beyond 

 the upper ; in tessellaris these points are 

 also present, but the upper one is slightly 

 longer than the lower, the two closely 

 ovei lapping, almost appearing as a 

 single point. The parts seem slighter 

 and more transparent than the corres- 

 ponding ones in harrlsii. From the 

 above facts, I conclude that Halisidota 

 harrisii Walsh, is a distinct species, 

 entitled to stand as such in our lists. 



The fact that it is not to be distin- 

 guished from H. tessellaris in markings 

 can not militate against this conclusion, 

 as there is no essential reason why two 

 species should differ in markings except 

 that they naturally would do so in most 

 cases, owing to their not intercrossing. 

 We can hardly suppose that the special 



markings of a species afford a means of 

 recognition for the individuals of it, 

 except in a general way, as this would 

 imply too nice discrimination in these 

 insects. But that they can discriminate, 

 even in rubbed and faded examples 

 which would be the despair of an ento- 

 mologist, there can be little doubt, 

 though I can not believe that they do 

 this by the sense of sight alone. 



In New York state there are two 

 other species of Halisidota, namely H. 

 caryae and H. maculata, that stand to 

 each other in much the same relation as 

 H. tessellaris and H. harrlsii. but the 

 differentiation seems to have progressed 

 further, so that they are readily separable 

 in the imago state. H. caryae has nine 

 stages, as I have already recorded in 

 Psyche, while H.tnaculata, has but seven 

 to judge from the last two, which are 

 all I have observed. In the last stage, 

 caryae has a width of head of about 4.3 

 mm., while maculata has one of 3.2-3.6 

 mm. 



Halisidota harrisii Walsh. 



Egg. Rounded, obtusely conoidal, the 

 base flat; very shiny pearly greenish white; 

 diameter 0.7 mm. Laid in a mass of about 20 

 on the under side of a leaf of the food-plant. 



First larval stage. Head pale whitish, 

 eyes black, mouth brown; width 0.4 mm. 

 Body whitish, the warts concolorous, each 

 bearing a single blackish hair. 



Second stage. As before except that the head 

 is 0.6 mm. wide and the hair is more abun- 

 dant, several from each wart, longest near 

 the head. It is whitish, mixed with shorter 

 stiff black hairs. 



Third stage. Head as before, width 0.9 mm. 

 Body whitish, with a row of blackish subdor- 

 sal dashes on the middle segments. Warts 



