110 LYMANTEIIDAE. By Dr. E. Strand. 



The funnel-shaped warts are said to serve as defensive organs against the attacks of Ichneumons, 

 etc., probahly givinj,' off a nauseous scent imperceptible to us. They are reversed by the pressure of the 

 blood and retracted by muscular action. In some species (e. g. Lymantria monucha and concolor, Hypo- 

 gymnia viorio) they are quite small. They are known from several Indian species, e. g. Euproctis plana, 

 ritellina, guttata and scintiUans, Laelia exclamationis, Dasychira inclusa (dalbergine), etc., while in the larvae 

 of some Indian Dasychira they are said to be probably absent. The hairs of the before-mentioned tufts 

 and brushes is spun into the cocoon by the larva, and in some species produce an inflammation on the 

 human skin. The hairs of young larvae of Lymantria are distinguished by bladder-like swellings (aero- 

 phores), whereby the specific gravity- is diminished and the possibility of the larvae becoming dispersed 

 is increased. Most larvae of Lymantriids are short and stout, and in the dense covering of hair resemble 

 the larvae of tiger-moths. They live more often on trees than on herbs and usually hibernate as larvae ; 

 the cocoon is sometimes double and the pupa is slender (pupa obtecta), soft-skinned and sometimes very- 

 hairy. The larvae of the (5'(^ are often smaller than those of the $$. When touched the Lymantriid 

 larvae do not roll up and are mostly rather sluggish. Exceptionally (e. g. in Lymantria dispar) they are 

 cannibals. 



Some of the Lrjmantriidae are the insects most noxious to cultivation, especially notorious being 

 the Black Arches {Lymantria monacha) and the Gip-sj- moth (L. dispar) (the name Lymantria meaning 

 destroyer). Gynandromorphous specimens have frequently been observed in L. dispar, and lately B. Brake 

 has bred whole series of interesting gynandromorphs by crossing aUied races. The Lymantriids usually 

 hibernate as larvae. 



The position of the wings differs sometimes rather considerably even in otherwise closely allied 

 species, as e. g. Arciornis l-nigrum and Stilpnotia salicis. The wings of several species bear poisonous hairs. 



It is not always easy to distinguish the different species of these insects. In many cases it is 

 possible to find new characteristics not as yet known or taken into account, e. g. the anal tuft of the $ 

 of Euproctis chrysorrJwea consists of simple tliin filiform hairs, while in E. transversa Moore from Java 

 it is formed of broad lanceolate scale-hairs, so that these two species can without difficulty be distinguished 

 bj^ the anal tufts alone. 



The most notorious among the noxious Lymantriids is the „black arches" moth {Lymantria mon- 

 acha). The species is generally comparativeh' sparse even in forests which are unusually favourable for 

 their rapid increase, but when they once begin to multiply their number grows astoundingly in a few- 

 years. The moth is not remarkably fertile, only laying about 100 eggs, but all the same the number of offspring 

 of a single specimen after 5 generations is said to reach four or five millions, even apart from the large 

 number which have in the meanwhile been destroyed by various enemies. Many remedies for getting 

 rid of this plague have been tried in vain; even infecting them with fungi has met with little or no 

 success. But many larvae perish from a natural disease caused by fungi. It also appears that after 

 some time the persistent increase of specimens in one locality is arrested by the disparity in the number 

 of specimens in the two sexes. At the height of such a devastation, migrations of large swarms of this 

 moth have frequently been observed, the insect thus often invading far-off districts which until then had 

 remained free from attack. Such migrations also occur among other Lymantriids, e. g. Stilpnotia salicis. 

 In consequence of their habit of coming down the trees and crawling up the stems of others it is possible 

 to mitigate the destruction by putting limed rings around the trees. Another of our most noxious species 

 of Lymantria, L. dispar, was in 1868 or 1869 introduced into N. America, wdiere it since 1879 occurs in 

 iumaense numbers and under the name of Gipsy moth has become known as one of the worst insect- 

 plagues, being there much worse than in Europe. From 1889 to 1897 no less than 750 000 dollars were 

 granted by the government of the States for the destruction of this insect. 



Among the parasites of the Lymantriids one of the commonest is Pimpla instigator, which infests 

 the pupae of Ocneria, Porthesia, etc. 



Lymantria dispar is a favourite subject for research on questions relating to sexual distinctions, 

 as e. g. experiments in castration. The larvae of dispar are an ideal subject for such experiments, and 

 on account of the strong sexual dimorphism the fully developed moth is also very suitable for this purpose, 

 all the more because the species is particularly interesting on account of the frequency of gyandi'O- 

 morphous specimens. By these experiments in castration the following results have been obtained, inter alia, 

 which are doubtless of wider bearing or may even be of general application. The size of the genital glands 

 and the capacity of the abdomen are correlative. But castration has no effect whatever on the secondary 

 sexual characteristics, the genital glands not at all influencing the development of the secondary- sexual 

 characters. These glands do not influence the characters of the regenerated wings, nor has castration 

 any influence whatever on the psychic differences of the sexes (Oudemans, Meisenheimer.) 



We divide the family into two groups, viz.: Areolatae, in which an areole is often present, and 

 Inareolatae in which it is always absent. Whether the areole is present or not has no great significance, 

 as in some species both is the case, the areole being sometimes present in one wing, absent in the other. 



