>T - 



454 ENTOMOLOGICAL NEWS [Dec., 'l 



Petiole of abdomen rather strongly, but very gradually widened at 

 apex, its spiracles at the posterior third not at all prominent. Ovipositor 

 as long as the three basal segments of the abdomen taken together. 

 Hairs on abdominal segments sparse and weak. Tooth on hind femora 

 well developed, acute; spurs of hind femora subequal, barely over one- 

 third the length of the metatarsus. Wings with a rather large oblique 

 areolet; median and submedian cells of equal length. 



Type from Cape Haitien, Haiti ; collected by Dr. W. M. 

 Mann. 



This is similar to E. aztecum to which it will run in Cock- 

 erell's table 2 and in my own : , but differs from the Mexican 

 species by its much smaller size and in the color of the legs. 



Dytiscus as a Destroyer of Mosquito Larvae (Col., Dipt.). 



Larvae of dytiscids or diving beetles, the water tigers, have long been 

 considered important enemies of the mosquito. Dr. J. B. Smith and 

 others have performed laboratory experiments in which they showed 

 that a single water tiger placed in a jar containing many mosquito 

 larvae will kill or devour large numbers of them. Smith mentions (Re- 

 port New Jersey State Agr. Exp. Station, 1904) a single experiment in 

 which a water tiger killed or devoured 434 mosquitoe larvae in two 

 days. He considers the water tigers as extremely important agents in 

 the control of the salt marsh and fresh water mosquitoes. 



The writer has observed in the field that many larvae are found in 

 pools also occupied by the dytiscids. A few laboratory experiments 

 showed that a single water tiger placed in a small jar containing many 

 mosquito larvae did kill or devour tremendous numbers. 



Three experiments were then performed in the .laboratory using a 

 few larvae only. Aquarium jars II inches in diameter and 7 inches in 

 height were filled to about two-thirds their capacity with water. In 

 each of them five water tigers were placed and were allowed to accus- 

 tom themselves to their environment for a period of about an hour. 

 Then to each of the iars were added 20 mosquito larvae of the second 

 molt of the species Culex pipiens. At the end of 8 days jar No. i (-till 

 contained 12 active mosquito larvae, jar No. 2 contained 9 living indi- 

 viduals and in jar No. 3 but 2 larvae remained. All the water tigers 

 survived the experiment. Later experiments performed with single 

 water tigers and the same number of mosquito larvae gave approxi- 

 mately the same results. 



It would seem that the dytiscids may be of great importance in kill- 

 ing larvae when present in tremendous numbers, but that where the 

 larvae are distributed pretty widely, there is little liability of their 

 complete extermination by such an enemy. F. E. CHIDESTER, Rutgers 

 College, New Brunswick, New Jersey. 



2 Proc. U. S. Nat. Mus. vol. 46, p. 62. (1913). 

 ? Tsyche, vol. 18, p. 21 (1911). 



