336 



Leech and Chandler: Coleoptera 



Fig, 13:33. Helophorus aquaticus, head and prothorax of adult extablishing on air funnel to renew 

 its air supply; dotted portion represents air (Hrbacek, 1950). 



pairs of well-developed biforous spiracles. The larvae 

 of Berosus (fig. 13:37a) have abdominal gills contain- 

 ing tracheoles, hence need not come to the surface 

 to breathe, and are able to live in deeper water, far- 

 ther from shore, than are other hydrophilid larvae. 



Life history. — Adults of many species of hydroph- 

 ilids fly well, and like the Dytiscidae have spring 

 dispersal flights, usually in April and May. The life 

 cycle is completed during the summer, and there is 

 commonly a dispersal of the newly emerged adults in 

 August and September. At such times, especially in 

 the spring, the flying beetles may be attracted in 

 thousands to electric and other lights. 



The eggs are usually laid in the spring, but some 

 species oviposit throughout the summer. Eggs may be 

 deposited singly (Hydrochus spp., some species of 

 Berosus), or collectively. The egg mass is enclosed 

 in a nearly transparent bag-shaped case and carried 

 by the female beneath her abdomen in the genera 

 Helochares (fig. 13:35a), Epimetopus, and Spercheus 

 of the exotic allied family Spercheidae. In other known 

 examples the eggs are either embedded in a loose 

 web (Sphaeridium, Cercyon, Cymbiodyta, Paracymus) 

 or a blanketlike covering (Coelo stoma), or completely 



Fig. 13:34. Hydrophilidae. o, Helophorus aquaticus, adult 

 taking in fresh air at the water surface; dotted area indicates 

 the region of the air funnel; b, Hydrophilus alerrimus, adult 

 obtaining air with body deeply submerged; dotted area indicates 

 air film; c, Hydrochus elongatus, head and prothorax of an adult 

 approaching the surface of the water to replenish its air supply; 

 dotted area indicates air film on beetle (Hrbacek, 1950). 



enclosed in a silken case which has a vertical mast 

 or flexible ribbon attached (Helophorus, some Berosus 

 spp., Hydrophilus, Hydrochara, Laccobius, Anacaena, 

 Hydrobius, Enochrus). Eggs of the terrestrial Sphaeri- 

 diinae (Sphaeridium, Cercyon, Coelostoma, above) are 

 laid in damp or wet places; those of the aquatic 

 hydrophilids are in the water. 



The larvae are usually found during the summer 

 but some species are reported to pass the winter in 

 both larval and adult stages. There are normally three 

 larval instars, the first two of short duration. In most 

 species the newly hatched larvae swallow some of 

 the air trapped in the egg case (fig. 13:30c?) and are 

 thus able to float to the surface and take in fresh air 

 in the regular manner. Otherwise they must laboriously 

 crawl up, or drown. When mature, most aquatic larvae 

 crawl up onto the shore and burrow into the damp soil, 

 where some make well-defined pupal cells (see figs. 

 14, 15, in Wilson, 1923a). A typical pupa (fig. 13:39a) 

 has long spines which keep it from contact with the 





Fig. 13:35. Hydrophilidae. o, Helochares maculicolli s, ventral 

 view of egg case, detached from abdomen of female; b, Phaeno- 

 notum sp., undersurface of adult to show lack of carina on first 

 abdominal sternite; c, Dactylosternum sp., undersurface of adult 

 to show carina on first abdominal sternite (a, Richmond, 1920; 

 b,c, Horn, 1890). 



