LACHNEIDES. 439 



a large many-haired wart, as in the Anthrocerids. On the other 

 hand, in Trichiura, Lachneis, and Malacosoma, ii is very ill-developed, 

 i being much larger. In the last-named genus iii is a single-haired 

 chitinous-based, generalised tubercle, whilst in Trichiura, iii and 

 iv -4- v form large many-haired Avarts as in Pachygastria, Lasiocampa, 

 Eutricha, &c. The character of the tubercles in the first instar is well 

 illustrated by the following table drawn up by Bacot : 



Poecilocampa. — i smaller than ii, both many-haired warts, iii small (2 or 3 

 hairs), iv and v close together, many-haired warts (iv larger than v). 



Trichiura. — i large many-haired wart, ii small single-haired tubercle, iii many- 

 haired wart, iv + v a combined many-haired wart. 



Lachneis. — i larger than ii, i with 3 or 4 large hairs, ii very small with 2 small 



Malacosoma. — i much larger than ii, both chitinous warts, i large and bearing 

 4 or more large hairs, ii small and bearing only two small ones, iii a single-haired, 

 chitinous-based, generalised tubercle, iv and v represented by a double generalised 

 tubercle bearing 2 hairs. 



Pachygastria. — i and ii large many-haired warts, i larger than ii, iii a many- 

 haired wart, iv + v a large many-haired wart ; also a supplementary prespiracular. 

 many-haired wart (? newly-developed not a primary tubercle). 



Lasiocampa. — i and ii large, many-haired flattened warts or cushions, much 

 more specialised and flattened than in Pachygastria and Poccilocampa, iii large, 

 many-haired, more wart-like than i and ii, iv + v large, many-haired wart; a 

 large supplementary prespiracular on anterior edge of segment. 



Cosmotriche. — i large and many-haired wart, ii smaller (but still large) many- 

 haired. 



Eutricha. — i and ii large many-haired warts, iii large many-haired wart, iv + 

 v very large ; supplementary prespiracular on anterior edge of segment. 



Dendrolimus. — i large many-haired wart, ii also large and many-haired (but 

 smaller than i), iii a large and many-haired wart, iv + v large many-haired wart 

 (rather posterior); supplementary prespiracular many-haired wart also present. 



For comparison the tubercles of Bombyx mori have been worked 

 out, and result as follows : 



Bombyx mori. — i large, flat, with 4 setse, ii minute, a chitinous button giving 

 rise to a single hair, iii small, bearing 2 or 3 hairs, iv is post- and v subspiracular. 



Bacot further notes that " compared with the Psychids, Noctuids, 

 &c, we are on the whole correct in saying that the more generalised 

 larvae of the Lachneids have lost the generalised tubercles and setae, 

 whilst the more specialised larvae are in a fair way to lose the many- 

 haired warts that replace the primitive tubercles in the first instar as 

 well. In all the Lachneid larvae examined, with the exception of P. 

 populi, i is larger and more important than ii. The reverse is the case 

 in P. populi, and may point to the species having branched from the 

 primitive stock much earlier than the others (a view supported to some 

 extent by the characters of the egg), or, more probably, it may merely 

 be an aberrant development from some unexplained cause. In this 

 connection Ave may suppose that only a slight tendency to have a Aveak 

 ii Avas present in the primitive stock, or we may assume that it was as 

 strongly marked a character as in Malacosoma, in Avhich genus 

 degeneration has not even yet gone so far that it might not, under 

 special conditions, increase at the expense of i. The chief reason for 

 holding the vieAv that the large size of ii in P. populi may be a special 

 development is, that the lateral tubercles of P. populi are not so 

 generalised as in Malacosoma in the first instar. It may be here 

 remarked that the general dwindling tendency of ii observable in the 

 Lachneids is also \ r ery strongly marked in Bombyx mori Avhich is 

 presumably related to the Lachneid as well as to the Saturniid and 



