220 NATURAL HISTORY OF BHOMPSTON POND. 



which also bears two hairy appendages (b), enabling the larva 

 to suspend itself from the surface film, thus keeping its 

 tracheal system in communication with the air. The head 

 of this larva is shown in fig. 63 ; it has no mouth, but instead 

 it possesses two sharp sickle-shaped tubular mandibles (a), 

 by means of which it can imbibe the juices of prey. Near 

 the eyes (b) arise the antennae (c), while in front between 

 the mandibles are the maxillae (d), with their maxillary 

 palps (e) and the labial palps (f). 



Colynibetes fuscus (fig. 65) was also taken together with a 

 much commoner beetle (Ilybius ater). The tracheae of these 

 beetles open into an air space between the abdomen and the 

 elytra, an arrangement which enables them to remain some 

 time under water. When the air in this chamber is exhausted 

 they rise to the surface and, lifting their Aving cases above 

 water, they take in a fresh supply of air. These insects 

 are carnivorous, readily attacking even the newt larvae of 

 the pond. To enable the male to hold on smooth surfaces, 

 the three basal joints of the first tarsi are expanded into 

 adhesive disks, and those of the second pair of legs are also 

 modified. In the latter of the above mentioned beetles 

 the three proximal segments of the anterior tarsi bear adhesive 

 hair-like structures (fig. 66) in the case of the males. The 

 third pair of legs in both sexes are flattened and are furnished 

 with setae for the purpose of swimming. The gnathites 

 are adapted for biting. The labrum (fig. 67) is simple and 

 trans verse, the mandibles (fig. 68) are short, thick, and strongly 

 toothed. The basal part of the first maxilla (fig. 69) is the 

 protopodite, i.e., the stipes (a) and cardo (b). The endopodite 

 consists of the lacinia (c), bearing a masticatory fringe (d), 

 and the galea (e) and the exopodite is represented by the 

 maxillary palp (f). In the labium (second maxillae (fig. 70) 

 the endopodites (b) and the protopodites (c) are fused together, 

 but the exopodites are represented by the three- jointed labial 

 palps (a). 



As might be expected the " Bloodworm " is present in 

 the pond. This insect, the larva of Chironomus, forms 





