sc//':\CE-aossj/'. 



295 



ritniilics. Tlicir use here is not very nppiirvnt, 

 lis llicy soi-iii loo small to Ijc of service in break- 

 ing and siraping the coiiipariUively hard surface 

 111' the pupji case. A similar strucliire is to be found 

 on the ovi|K)sitor and genitalia of some Diptera, 

 Apidac, and Coleuptera, where it is protxibly for 

 sensory purpases. This fact rather confuses than 



Kn;. 3. Ht'itd oi S. ////ar/,1, >Iinwiiig ptiUiuini expanded. 



throws light mi llie uses ul llic -.InicUire » htii [ilaced 

 on the ptilinum. 



On the sides of the thorax of Stonio.\ys calcilrans, 

 the familiar blood-sucking Hy, between the fore and 

 middle legs, on that part of the thorax technically 

 known as the meso-epimerum, are two patches of this 

 characteristic membrane, though not ()uite identical 

 under a power of 350 diameters with that on the 

 head. I believe these have not been before noticed, 

 and are indeed difficult to make out. They show 

 well enough on a cleared and mounted insect, but 

 only appear as a darker spot on the body when 

 examined .is an opaque object. They are about the 

 same size .as the spiracles, though totally different in 

 appearance. It has been the custom of observers on 

 finding an organ whose use is not apparent to class 

 it as auricular. The comb on the fore tibia of many 

 I lymenoptera, used for cleaning the antennae, was 

 explained thus, and it is possible that these may be 

 for auricular purposes. That being so, one would 



i 





Fic".. 4, Minute scales of ptilinum. 



expect to find it on nearly related species. I have 

 carefully examined a number of Muscidac, but failed 

 to find it ; therefore, arguing from analogy, I am 

 inclined to think that they are used in the same way 

 as the ptilinum and for the same purpose, and add 

 another complication to the anatomy of this already 

 highly specialised insect. 



go Belsize Road, South Haiiipslcad, K. II'., 

 February znj, 1900. 



NOTES 0\ VVOODLK K. 



liv Wiiiiti-.ii Makk Wijiii, I'.L.S. 



'T'lIEKK is no doubt that among crustaceans the 

 woodlice are very much left to themselves by 

 naturalists in this country. Here and there, how- 

 ever, one finds that some trouble has lieen spent 

 upon these creatures, and quite recently a paper deal- 

 ing with them was re.id before the North London 

 Natural History .Society by Mr. James B. Casserley. 

 It is mainly to record some facts brought fcjrward in 

 this contribution that the present article has been 

 written. 



Of greatest interest are the remarks with regard to 

 Ariuadillidiuni Tu!f;art' Latreille, based upon notes 

 made daily from June to December 1897. Kor some 

 weeks the developing young could be seen through 

 the «all of the brood-jjouch formed by plates on the 

 under side of their mother, in which the eggs are 

 carried about after they are laid. On July 18th a 

 brood was found struggling about among the lumps 

 of mould in the breeding-cage, each individual being 

 about the size of an ordinary pin"s-head. .Smaller 

 parents, it was noticed, had proportionately smaller 

 otTspring. As soon as they had quitted the brood- 

 pouch, the young woodlice began to run about briskly, 

 and were able to roll themselves up into balls in 

 exactly the same waj' as do the adult members of 

 their particular species. They were white in colour, 

 and apparently resembled their parents in structure, 

 save that while the latter liave seven pairs of walking 

 legs, the former had but six pairs. Owing to the 

 cannibalistic propensities of the older woodlice, Mr. 

 Casserley was not able to observe the first moult, 

 after which the seventh and hindermost pair of limbs 

 is found to be present. 



The conclusion that was arrived at is that woodlice 

 must live a considerable time. During the six 

 months that they were watched, no individual 

 changed its skin more than once, and the increase in 

 size after moulting was so slight as to be but barely 

 perceptible. It is only reasonable to think that a 

 long period will be required, under these circum- 

 stances, for a creature the size of a pin's-head to 

 grow to a length of three-quarters of an inch. It is 

 worthy of note too, that Armadillidium goes on 

 growing after it is sexually mature. 



The larger the animal the darker is its hue, 

 until a length of the third of an inch has been 

 reached ; then the characteristic slaty-black colour is 

 aci)uired. Mr. Casserlej is at a loss to explain the 

 variation that occurs in the number of the green 

 spots that were distinguished on the dorsal surface of 

 every specimen, with the exception of one or two 

 large ones. Two examples of the same age would 

 change their skins at the same time, says the ob- 

 server, and after moulting one might have the numlicr 

 of decorations nearly doubled, on the other very few- 

 could be seen. 



The following description of the process of 



