200 INSECTS IN SPONGILLA FLUVIATILIS. 



hands are most usefully engaged : indeed, after fifty years of 

 constant use of the microscope, I can truly say that it is only 

 now that I am perfectly satisfied in the employment of that 

 instrument. — Thomas Gill. — 125, Strand, March 23rd, 1839. 



Anomalous Insect found in Spongilla Jluviatilis. — At the 

 meeting of the Entomological Society held on the 3rd of De- 

 cember, 1838, Mr. Westwood read the description of a minute 

 and anomalous species of insect recently discovered as the in- 

 habitant of the Spongilla Jluviatilis. These little insects are 

 scarcely more than one eighth of an inch long, and of a pale 

 green colour, with six moderately long legs, having, at first 

 sight, much of the appearance of Aphides. They are, how- 

 ever, apterous, and of a very peculiar structure, so that not 

 only is the family doubtful to which they belong, but even 

 the order and class. The antenna are about half the length 

 of the body and very slender, and the mouth consists of four 

 naked seta, exceedingly delicate, porrected, and equalling 

 the antenna in length ; they arise in pairs at a short distance 

 apart, and are not inclosed in any sheath, like the setce of 

 Hemiptera. The body is clothed with numerous long hairs, 

 and each of the abdominal segments is furnished at the sides 

 with a pair of long, flattened, articulated filaments, somewhat 

 like those of the larva of Sialis lutaria, which are evidently 

 organs of respiration, and are kept in constant agitation in 

 their watery abode. Mr. Westwood is doubtful whether, not- 

 withstanding several of their characters, these insects ought 

 not to be regarded as having arrived at their full growth, as 

 they possess certain points of resemblance with the perma- 

 nently apterous Coccida and Aphida, whilst there is no tribe 

 or family of insects of which they can be regarded as the lar- 

 va, (except perhaps the anomalous genus Acentropus, that 

 has been regarded by Stephens as Neuropterous, Curtis as 

 Trichopterous, and Westwood as Lepidopterous, and of which 

 the larva is unknown). 



Mr. Hogg, F.L.S., by whom these insects were discovered, 

 during a series of minute investigations upon the Spongilla, 

 has arrived at the conclusion that the motions of these in- 

 sects, and the undulations which they produce in the water, 

 have been mistaken by Laurenti and others for movements of 

 the sponge itself, and which they have accordingly regarded 

 as affording proofs of the animality of that substance. 



