26 ASTACID^E. 



The wings are either long and well developed, or .short, or entirely 

 wanting. The short-winged Orthoptera (Gryllus, Locusta, Blatta, Perla, 

 Termes, Psocus) have been carefully described by Messrs. Fischer, Von 

 Siebold, Lucas, Brauer, and myself; the short-winged or apterous 

 Hemiptera, by Westwood and Uhler (Amphibiocorisiae, Gerridae, etc.) ; 

 the short-winged Diptera by Schaum ( OrmthoUa and Lipoptera). Mr. 

 Brauer has recently given an interesting paper upon dimorphism in the 

 genus Neurothemis, which belongs to the Odonata. The dimorphic 

 females have wings with a less complicated neuration and different 

 colors. There is even a case of trimorphism in some butterflies, accord- 

 ing to the observations of Mr. Wallace. PapiUo Ormenus, from Celebes, 

 has three distinct forms of females, and in some cases the number of 

 female forms appears to be four. Dimorphism consisting in different 

 shape and size is observed in the Lepidoptera (Equites, etc.), in the 

 Coleoptera, in the Lamellicornia, and in the Longicornia, and perhaps in 

 the Lymexylon and Hylecoetus ; in the Hymenoptera (Cynips) ; in the 

 Diptera (Phasia). The dimorphism in the Dipterous genus Phasia, dis- 

 covered by Loew, is very remarkable. Having seen his specimens, I 

 may be permitted to add here a written communication by Mr. Loew, 

 sent to me some years ago and still unpublished : - In the genus 

 Phasia every species has two male forms ; one similar to the female, 

 and another much larger, with the wings broader and more colored, 

 and usually the body more colored. The two forms fly at the same 

 time and unite with the same form of females. The genital parts of the 

 larger. males are in shape and size identical with those of the smaller 

 males. There exist some intermediate forms of males, and it is some- 

 times, in certain species, possible to form a complete series, which seems 

 to unite the two different forms. I say seems, because I have never 

 seen a male which I hesitated to place in one of the two forms." 



I have noticed here the occurrence of dimorphism in the insects to show 

 how variable in the different families and genera is the mode of dimor- 

 phism, even from that observed in the Astacidce. Perhaps a closer 

 examination will disclose even some difference in the sexual parts in 

 certain dimorphic insects, and it now seems probable that some forms, 

 heretofore described as distinct species, will be hereafter recognized as 

 only dimorphic variations. Still, it is possible that very different facts 

 are to-day united under the same name of dimorphism. 



Certainly the discovery of a dimorphism in another part of the Artie- 

 ulata, viz. in the Crustacea, leads us to suppose that it will be found 

 also among the worms. 



The Rarity of Varieties is mi Important Character for Cambarus. — The 

 rarity of varieties in the genus Cambarus is worthy of remark, and may 

 be considered as an important character of this genus. In the true 

 . 1 iacus, the two species living in Europe vary so much that even by 



