THAXTER. — MONOGRAPH OF TFI 10 LA HO ( T LH 10 \ I A( ' 10.10. 



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production of secondary appendages. Similar tendencies toward irregular division of the appendages, 



as well as of cell IV and of the inserf ion-cell, are also seen in L.CHvmalis (Plate LXI) and several allied 

 species, although a, perfectly normal type may be associated as in this species, with such abnormalities. 



It is evident that this large genus is a modem one, in which species making is in active progress, 

 and it is thus an extremely difficult one to treat from a systematic standpoint; especially in view of the 

 limited material usually available for study, and the poor condition in which such material is found in 

 collections, on dried insects which have in general been previously soaked in alcohol, and it must often 

 be a matter of opinion whether species, or varieties, or regional variations are in question. In endeavor- 

 ing to put in order the almost endless variations of the simpler, or " fiagellata" type, I do not feel that I 

 have in all cases been consistent in my view of what constitutes a variety and what a species. For example 

 under L. Tcxana and L. proliferans certain apparent variations are distinguished by varietal nanu s, 

 while from orientalis I have separated as species, L. japonica, L. pusilla and L. rhinopkora, although 

 the differences in these cases are no greater, perhaps, than they are in cases where the varietal designation 

 has been applied. I do not feel at all sure that it would not have been better to discard varietal designa- 

 tions entirely, or at least in L. Texana, L. proliferans and L. cauliculata, in recognition of the fact that in 

 these cases species making is in progress, although the forms do not appear to have become so well defined 

 as they are, for example, in a majority of the numerous closely allied species of the remarkable "Galeritce" 

 group. 



Apart from a crowd of forms which it is very difficult to assemble about any very definite type species, 

 there arc several subdivisions of the genus which may be distinguished with some definiteness; and among 

 these that which occurs on water beetles belonging to the Gyrinidae, and which may be grouped about 

 L. Gyrinidarum as a type, is perhaps one of the most clearly defined. This group, instead of suggesting 

 primitive conditions, which might be expected to throw light on possible aquatic ancestors of the family 

 as a whole, appears to illustrate, rather, one of its most highly developed types, as is indicated by the greater 

 complexity of the receptacle, appendages and, in many cases, of the perithecium. The more complicated 

 members of this group, however, are directly connected with the terrestrial types through forms like L. 

 variabilis; while it contains within itself a certain number of simpler forms like L. coarctata, for example, 

 in which the receptacle is absolutely normal. Among these aquatic species, of which there are about 

 twenty, L. aquatica alone shows a copious development of typical flask-shaped antheridia, while in the 

 others no bodies have been observed which can certainly be regarded as organs of this nature. It should 

 be mentioned, however, that material of these forms is almost invariably in bad condition, and that I 

 have made no attempt to reexamine fresh material of the common forms on American Gyriui in order to 

 determine this point. 



A somewhat similar and very curious tendency to secondary division, not only in the distal cells of 

 the receptacle, but in the basal cells of the appendages as well, is also seen in the group of forms referred 

 to above, occurring on Clivina and allied carabid genera Schizogenius, Morio, etc., although in these cases 

 the tendency has not become fixed, as is illustrated in figures 5-G of Plate LXI. 



As might be expected in a genus which includes more than two hundred species, the parasitism of 

 the latter is unusually varied; and although the Carabidse among the beetles harbor the great majority, 

 forms are known to occur on Staphylinidse, Gyrinidae, Cicindelidse, and several other orders among the 

 Coleoptera; on Diopsidse among the flies; on Termites among the Neuroptera; on two Gamasid mites, 

 and even on ants. It is rather remarkable that such extreme differences in hosts have, in most instances, 

 induced no considerable departure from the conventional type, even in cases where the character of the 

 host is so unusual as in those of L. Hageni and L. Formicarum which occur on Neuroptera and Hymenop- 

 tera. Whether the forms on Gamasidse (L. armillaris and L. Napoleoiiis) are aberrant, it is hardly possible 

 to determine from the published figures; but these hosts might certainly be expected to harbor very peculiar 

 species. 



The distribution of the species corresponds in some instances to that of the genus of host insects, as 



