NATURAL SCIENCES OP PHILADELPHIA. 33 



onidae, etc., remarkable gradations can be established. The 

 highest perfection in the art of cocoon-manufacture is attained by 

 members of the old Linnaean genus, Attacus. Between the lowest 

 moths and the lowest type of butterflies a wide gulf intervenes. 

 This is bridged over by many small genera, which enable us to 

 reach the latter by a slightly circuitous course. Leaving out the 

 genus Attacus, there seems to be a more nearly continuous route. 

 May not certain members of this genus constitute the extreme 

 limits of one or more branches of the great tree of lepidopterous 

 life 



The small loop by which a Papilio or a Vanessa suspends itself to 

 a support, when about to pass into a pupa, and the girdle which 

 it throws around the middle of its body to prevent unlimited and 

 undue motion whereby injuries are prevented, are, it seems to me, 

 but the last traces of the cocoon with which in primitive times it 

 was wont to inclose itself. Indeed, there is a Brazilian moth of 

 the subfamily Tineina which swings itself from a twig \>y means 

 of a compound silken thread, thus imitating, though on a grander 

 scale, man}- of our Papilionidse, after which it spins a cocoon, a 

 perfect network of fibres, so loosely arranged that the chrysalis 

 may be discerned in all the distinctness of its parts. In this in- 

 stance, the sole object of the cocoon, if there can be no impro- 

 priety in recognizing it as such, is not to protect its inmate from 

 the inclemency of the weather, but to be, as it were, a domicile in 

 which the almost immobile pupa can sleep until it wakens to new- 

 ness of life. In point of utility this cocoon, judging from the 

 laxity of its formation, is but little superior to the slight silken 

 covering with which some of our earth-seekers line their cells. 

 Alucita porectella builds a somewhat similar cocoon ; but its 

 beautiful network, rivalling in beauty the mechanism of art, is 

 hidden away within curled-up leaves, or underneath them. There 

 is a very close resemblance in the cocoons of the above two spe- 

 cies. While the Brazilian larva utterly discards all extraneous 

 objects which would mar the beauty and transparency of its house, 

 Alucita porectella, for some unknown reason, selects a leaf as a 

 basis whereon to build its showy fabric, a very common occur- 

 rence. As far as my knowledge extends, these are the onty two 

 species of the family to which they belong that do not construct 

 cocoons of ordinary compactness. In Alucita, this marked loose- 

 ness is in a great measure atoned for by the leafy envelope 



