SPOTTED WILLOW- APHIS. 139 



This species belongs to the genus Lachnus, of Illiger, which differs 

 from Aphis proper in the shortness of the antennse, the seventh joint 

 being rudimental or wanting, in the very short and almost obsolete 

 honey tubes, and in the habit of the species of stationing themselves 

 on the limbs of trees instead of the foliage. 



1 cannot find that this species has been described, and Prof. Uhler, 

 of Baltimore, to whom I transmitted specimens, confirms this opinion. 

 Dr. Harris describes a similar species found on the pig-nut hickory, but 

 this is a much larger species and has but four rows of dots on the ab- 

 domen. The same author also describes a species found, like the pres- 

 ent, on the limbs of the willow, and also resembling this in staining 

 the fingers red, when crushed. But this is a smaller species and 

 wholly destitute of the characteristic dots on the abdomen. Dr. Fitch 

 also briefly describes a species found on the willow, under the specific 

 name, sallicelis, which he refers to the genus Lachnus ; but this is a 

 still smaller species, and also, so far as we can judge from the descrip- 

 tion, without spots on the abdomen. From the similarity in habit of 

 Dr. Harris' species just referred to, the suspicion arises whether that 

 may not prove to be an abnormal variety of the present species. In 

 that case Dr. Harris' species would stand as a variety of the present, 

 inasmuch as the specific name of Salicti, given by him to that species, 

 had been pre-occupied. 



In selecting a name for this rather large and well-marked species, 

 the term saliois — meaning, of the willow — which first suggested itself, 

 was abandoned on account ©f its resemblance to several other terms, 

 which mean essentially the same thing, and which have been alreadv 

 employed to designate other species of Aphides. The term salicis^ 

 itself, moreover, has been applied by Linnasus to a European species 

 of the genus Aphis, and it is always desirable to avoid the repetition 

 of the same specific term in naming the species of closely allied genera. 



The term punctatus, referring to the dots on the abdomen, would 

 seem to be very expressive, but it is not sufliciently characteristic. 

 Prof. Uhler informs me that all the species of the genus Lachnus in 

 his collection have the abdomen more or less spotted, so that this would 

 seem to be a generic rather than a specific character. I therefore 

 made use of the term dentatus, having reference to the conical or tooth- 

 like process on the middle of the abdomen, and which, so far as I can 

 learn, is peculiar to this species. 



