KHODOSTROPHIA. By L. B. Prout. 35 



species has been gained solely by obtaining eggs in captivity. The $9 deposit their eggs very readily, and many 

 of the species are quite easy to rear, the commonest weeds, such es knotgrass and da.ndelion, being willingly 

 accepted by most of them. They show a marked predilection for withering leaves, and some, indeed, thrive 

 well on food which is actually mouldy. In some cases there are two or more broods during the summer, but 

 many of the larvae grow very slowly, and produce only a single brood of imagines. The pupa is rarely, if ever, 

 truly subterranean, although many species, if provided with earth, will use it in the constructions of their 

 slight cocoons. The usual habit, however, is to spin up loosely among dead leaves or other refuse on the sur- 

 face of the ground. The remarkably different habit of the Cosymbia-group has been mentioned in our Intro- 

 duction. The colour is usually light brown, scarcely ever that reddish brown which is general among the 

 subterranean pupae. The surface is usually pretty smooth and almost, or altogether, without markings, but 

 some species of Ptychopoda are somewhat rougher, with the dorsal surface spotted and the wing-vems 

 strongly marked. The dui'ation of the pupal stage, except in hibernating Cosymbia, is generally short. The 

 method of dehiscence is characteristic, the anterior part of the pupa-case being much broken and the entire 

 thorax strongly cleft dorsally, the edges at the point of cleavage bending markedly inwards. 



The moths as a rule fly gently at dusk or later and are usually found in la.rge numbers where they 

 occur, although many are excessively local ; several species will occasionally visit flowers or the sugar spread 

 for Noctuids, or may be attracted by a strong light. During the day they rest among bushes or herbage, a 

 few species, such as Acidalia mar^inepunctata, Ptychopoda eburnata etc., on rocks or stone wells. The majority 

 can easily be disturbed, and do not fly fast or far, so that their capture presents no difficulty. Sometimes 

 in their resting-places they are not even conceaied; thus Acidalia floslactata and Ptychopoda rusticata often sit 

 on the upper side of leaves, the latter species (and perhaps also the former) being sufficiently protected by a 

 resemblance to the excrement of birds. 



The Acidaliinae may be divided into 3 principal groups, one of which, the Cyllopoda-gnowji, belongs 

 to the Central and South American Region. The other two groups a.re of almost world-wide occurrence, al- 

 though very weakly represented in the Arctic regions and wanting in New Zealand and Hawaii, with the excep- 

 tion of a single (probably introduced) species in the former country. The typical or Acidalia-gxo\x]i has the 

 pupa normal, the imago with the first subcostal vein occasionally free, but if stalked or anastomosing with the 

 other subcostals, then separating early — usually weU before the fifth subcostal, the areole usually large, 

 not infrequently double, the palpus rarely long, the ^ a^ntenna mostly ciliate, the ^ hindleg very commonly 

 aborted, the ^ genitalia with the valve simple in form, only a long unarmed flap or a simple valve ending in 

 a curved head. Tlie Cosym&w-group has the pupa attached to a leaf by its tail and a silken girth, resem 

 bling that of many butterflies, the imago with the first subcostal vein stalked to (usually) well beyond the fifth 

 the areole usually very small or wanting, never double, the palpus often long, the ^ antenna strongly bipecti 

 natj, the ^ hindleg usually not aborted, the ^ genitalia with the valve of a much more complex structure 

 than in the Acidalia-gvowp . The larvae vill also probably present reliable distinctions; at present we merely 

 call attention to the less cylindrical form and strong rugosity of many of the larvae of the Acidalia group 

 and their attachment to low plants and larval hibernation, while those of the Cosj/mfeia-group affect trees 

 and hibernate as pupae. The preseijce of rounded white discal spots on one or both wings is also generally 

 indicative of a species of the C'os^/m^ia-group, but cannot be always relied upon. 



Neither the Acidalia- not the Cosymbia-gvouT^ can be regarded as arising at ail directly frjm the other; 

 each is the more specialized in certain respects, and they must have sprung collaterally from the primitive 

 Acidaliid stirps. It is also noteworthy that the genera with double areole (which, according to the usual con- 

 ception of phylogeny, should be older than those with single areole or with all the subcostals stalked) furnish 

 scarcely any exemples of unmodified hindleg structure; most of the genera in which both sexes retain all the 

 spurs are found among the groups with single areole or even (Chrysocraspeda) without areole. 



On account of the large number and general similarity of the species I have given somewhat fuller 

 descriptions, differentiations and synonymy here than in the other subfamilies. 



The Acidalia-group. 



Areole double (*) Genera 1 — 6. 



Areole single (**) Genera 7—23. 



1. Genus: Bhodostropliia Hbn. 



Palpus rather short or moderate. Antenna in (J moderately long, bipectinate, with slender branches, 

 two pairs on each segment. Hindtibia in ^ slender, with or without hair-pencil, with a pair of terminal 



*) The outer areole open at its distal end in Apostates. 



**) Occasionally open at its distal extremity, the first subcostal merely approaching instead of anastom.osing with 

 the others; see Ptychopoda and Cleta. 



