Keys to the Aquatic Genera 



of North American Scopeumatidae 



Adults 



1. Frontal bristles or hair long 2 



— Frontal bristles extremely short, the front nearly bare 



Hydromyza Fallen 



2. Front tibia without a short, rectangular apical spine 

 below Cordilura Fallen 



— Front tibia with a short, stout, rectangular spine at 

 apex of ventral surface Acanthocnema Becker 



Larvae and Puporia 



1. Pharyngeal skeleton with dorsal processes tapering 

 and extending further caudad than the ventral processes 

 (fig. 14:626); posterior spiracular discs brown, sep- 

 arated from each other by a distance of less than their 

 diameter, the lower spiracular process greatly elongated 

 (fig. 14:62a, d) Hydromyza Fallen 



— Pharyngeal skeleton with dorsal processes stout and 

 extending no farther caudad than the ventral processes; 

 posterior spiracular discs yellow, separated from each 

 other by a distance equal to or greater than their 

 diameter, the 3 spiracular processes of each disc 

 subequal and digitiform Cordilura Fallen 



California Species of Aquatic Scopeumatidae 



Genus Hydromyza Fallen 



There is but one North American species, H. confluens 

 Loew, which is northeastern and does not occur in 

 California. Studies by Needham (1908) and Welch 

 (1914, 1917) show that this species normally mines 

 the petioles of the yellow water lily in New York and 

 Michigan. Berg (1950) has also reared it from the 

 roots of Potamogeton in Michigan. 



Genus Cordilura Fallen 



: Frohne (1939) has published very interesting details 

 .of die life history of Cordilura latifrons Loew in 

 [Michigan. This species is a common stem borer of 

 I bulrushes (Scirpus spp.), attacking the bottom 15 cm. 

 j of the culms. 



California species: 



adrogans Cresson 1918. 

 amans Cresson 1918. 

 beringensis Malloch 1923. 

 luteola Malloch 1924. 

 masonina Curran 1931. 



Sonoma County 



Marin County 



Del Norte, Humboldt 



Humboldt County 



Fresno, Inyo 



REFERENCES 



BERG, C. O. 



1950. Hyurellia (Ephydridae) and some other acalyptrate 

 Diptera reared from Potamogeton. Ann. Ent. Soc. 

 Amer., 43:374-398, 4 pis. 

 FROHNE, W. C. 



1939. Biology of certain subaquatic flies reared from 



479 

 Wirth and Stone: Diptera 



emergent water plants. Pap. Mich. Acad. Sol., Art.s 



and Lttrs., 24:139-147. 

 JOHANNSEN, O. A. 



1935. See Diptera references. 

 NEEDHAM, J. G. 



1908. Notes on the aquatic insects of Walnut Lake. 



In A biological survey of Walnut Lake, Michigan, by 



Thomas C. Hankinson. Mich. Geol. Suxv. Hop. 1907: 



252-271. 

 WELCH, P. S. 



1914. Observations on the life history and habits of 



Hydromyza confluens Loew (Diptera). Ann. Ent. Soc. 



Amer., 7:135-147. 

 1917. Further studies on Hydromyza confluens Loew, 



(Diptera). Ann. Ent. Soc. Amer., 10:35-45, 1 pi. 



Family MUSCIDAE (including ANTHOMYIIDAE) 



This family contains such well-known pests as the 

 house fly, stable fly, horn fly, and the root maggots 

 whose larvae are saprophagous or phytophagous. The 

 aquatic muscids are predaceous and fall within scat- 

 tered groups of that section of the family which has 

 been known as the Anthomyiidae. The muscids may 

 be separated from the other suborders and families of 

 aquatic Diptera by the presence of a laterodorsal 

 longitudinal seam on the second antennal segment, 

 the thorax normally with a complete transverse suture 

 on the dorsum, the lower calypter usually large, the 

 postscutellum not prominent, and the hypopleura bare 

 or with only weak hair. The larvae are usually smooth, 

 tapering, and maggotlike (fig. 1 4: QZd,e, k, m); the head 

 possesses an internal pharyngeal skeleton (fig. 

 14:63/, Z) with well-developed pharyngeal sclerite, 

 short robust hypostomal sclerite, and long slender 

 mouth hooks often appressed together, the posterior 

 spiracles flush with the body surface or on short 

 elevations, the spiracular plates with well-developed 

 button and peritreme, and the slits short and radially 

 arranged (fig. 14:63w). The puparia (fig. 14:63c,A,/, q, s) 

 are usually ovoid and reddish brown in color. 



One North American genus which does not occur 

 in California has known aquatic larvae; Mydaeina 

 obscura Malloch from the Canadian Arctic was col- 

 lected in ponds where it is truly aquatic. Malloch 

 (1919) described and figured the larva and puparium 

 (fig. 14:63<?,r,£); the latter is very slender with a 

 remarkable subapical constriction forming a caudal 

 float chamber to keep the posterior spiracles in 

 contact with the water surface (fig. 14:63<?). Other 

 aquatic genera occurring in California are described 

 below. 



Key to the Aquatic Genera of North American Muscidae 

 Adults 



1. Anal (6th) vein extending to the wing margin 



Hydrophoria Robineau-Desvoidy 



— Anal (6th) vein not extending to the wing margin 

 2 



2. Palpi distinctly dilated at apices; parafacies and 

 pteropleura haired Lispe Latreille 



