Vol. xxvi] 



ENTOMOLOGICAL NEWS. 



299 



DIATOMS ATTACHED TO THE LARVAE. 



While examining the larvae and exuviae of Thaumatoneura 

 the great number of diatom shells attached to them was very 

 apparent. A single leg, which had been detached from an 

 exuvia, was sent to Prof. Albert Mann, Custodian in charge 

 of the Diatom Collection of the U. S. National Museum at 

 Washington, who has sent the following remarks on the dia- 

 toms adhering to this member: 



The species discovered on this very minute quantity of material are 

 as follows : 



Achnanthes ventricosa Ehr. 

 Cocconeis placcntula Ehr. 



and variety. 



Cymbella ventricosa Ag. 

 Epit hernia gibba (Ehr.) Kg. 

 E. gibberula (Ehr.) Kg. 

 E. zebra (Ehr.) Kg. 



and variety. 



Eunotia monodon Ehr. 



Gomphonema parvulum Kg. 



Navicula viridis Kg. 



N. oblonga Kg., var. 



N. n. sp. 



Nitzschia sp. 



Pleurosigma sp. 



Syncdra ulna (Nitz.) Ehr. 



Of the foregoing, Epiihcmia zebra is by far the most frequent. Corn- 

 phoncma parvulum next, Syncdra ulna next, Achnanthes ventricosa 

 next, and the others rather infrequent. The unnamed Nitzschia and 

 Pleurosigma afforded only one specimen each and their position was 

 such that I was unable to correctly identify them, but I am quite con,- 

 fident that they are not new. The new Navicula is extremely small and 

 very delicately marked, and I fortunately have two specimens. 



I should say that there were at least 500 diatoms on the small leg 

 of this larva. The most of these are forms that grow attached by a 

 transparent jelly-like stipe; but several of them are free and free-mov- 

 ing for example, the different species of Navicula. 



The finding of these forms on this aquatic larva is of importance be- 

 cause it helps to throw light upon a difficult problem connected with the 

 distribution of diatoms. It has always been more or less of a mystery 

 how isolated pools and bodies of water of recent origin become stocked 

 with a rather extensive diatom flora and frequently within a very short 

 period of time. Little is known regarding the spore formation of di- 

 atoms, investigations in this respect having been confined almost ex- 

 clusively to pelagic marine forms, such as Rhizosolenia. In most of the 

 genera no spore formation has ever been discovered. Some light has 

 been thrown upon this distribution by supposing these organisms are 

 carried on the feet of wading birds, but this method of transportation 

 is plainly very inadequate. If, however, we add to this transportation 

 by aquatic insects, many of which have the power of flying, we have 



