128 On Subaquatic Insects. 



their retreat — they were as lively as if they had been sporting in 

 the sunshine, instead of having been under water for more than half 

 an hour ! One point was clear, (confirmed by repeated observations 

 subsequently",) that these Brachelytrous insects have the power of 

 enduring submersion and under salt water for at least half an hour. 

 But why did they leave their burrows at a lower part of the sand ? 

 I had previously often collected on this spot, at different periods of 

 the year, during the neap-tides, and on the most brilliant days, with- 

 out having seen a single Hesperophilus on the wing. It is fair, there- 

 fore, to suppose either that the extraordinary flight I witnessed was 

 a mere casual occurrence, or that, in some way or other, it is to be 

 accounted for by the state of the tide. (It was the first of the 

 spring tides.) On this latter supposition these insects must have 

 been warned by some peculiar instinct to move higher up the sands, 

 and thereby to avoid submersion for a period that probably would 

 have exceeded their power of endurance." 



Now the observations of MM. Dutrochet and Audouin, and the 

 perfect analogy between the habits of the Hesperophili, Bledii, and 

 Aepus fulvescens, prove that the immersion of these insects was not 

 a circumstance to which they were unused. And hence, I think, 

 we must look for some other solution to the inquiry why these in- 

 sects were on the wing in such swarms, than that suggested by Mr 

 Rudd. 



In a later number of the same work, (No. 18, January 1837,) 

 Mr Haliday states that he found Cillenum laterale under stones near 

 low-water mark. " They prey upon sandhoppers, (Talitrus Locus- 

 ta, Leach.) The tide retiring has scarcely uncovered the sand 

 when these little depredators are abroad from their hiding-places, 

 and alert in the chase. A great part of their existence is passed 

 under the sea, and the mode in which they obtain the necessary 

 supply of oxygen during their prolonged submersion, when the 

 small quantity in the air bubble which they convey with them is 

 exhausted, seems to deserve a more particular investigation." As in 

 Aepus we find the mouth of this insect strongly developed, and the 

 fore-legs are constructed in a peculiar manner, (somewhat analogous 

 to those of Aepus noticed above,) the upper edge of the tibial notch 

 being furnished with two deflexed spines, between which the end 

 of the moveable spine arising from the opposite angle is received. 

 The spines attached to the basal joints of the anterior tarsi are also 

 very strong. Thus the structure of this insect is equally adapt- 

 ed for its depredatory habits, whilst the strong bristles with which 

 the limbs and body are furnished are similar to those of Aepus. 

 In company with the Cillenum, Mr Haliday discovered a new and 



