Pomona College Journal of Entomology 611 



SYRPHIDAE 



Always among the plant lice are to be found greenish, flat, sticky-looking 

 "worms" which are decidedly pointed at one end and which do not have a distinct 

 liead, eyes or legs. Tliese so-called "worms" are the larva- or maggots of a two- 

 winged insect or fly of the order Diptera and the family Syrphidae, which are 

 commonly called Sj'rphid or Flower-Flies. The larvae' (Figure 203 A) vary from 

 the minutest first-hatched maggot to nearly an incii in length, according to the 

 species to which it belongs. They are usually light or dark green, but some may 

 be brown, orange, very light or nearly black. Those feeding upon the citrus plant 

 lice and herein described are green with a longitudinal darker green or brownish 

 stripe on the dorsum. The mouth is situated at the small end and all of the food 

 is obtained by puncturing the body walls of the lice and then sucking out the 

 contents. This operation is easily observed in the field. The maggot firmly sup- 

 ports itself by the large posterior end, raises itself up and begins to blindly move its 

 mouth-end about in quest of food. If it touches a plant louse it immediately raises 

 it into the air and sucks it dry. This is very rapidly repeated, with very disastrous 

 results to the lice. When the larva is full grown it seeks some sheltered spot in 

 which to pupate (transform into the adult fly). This it may do on the stems or 

 upon the surface of a leaf. The pupa stage is shown in Figure 203 B and is a 

 long, roundish or oval, brown body, which shows no signs of life. From this 

 emerges the adult fly, which removes one end of the pupa case to escape. The 

 adults under consideration are dark with transverse yellow bands across the 

 abdomen as shown in the accompanying cuts. They are very swift fliers and are 

 often mistaken for bees. Thej' are common around flowers, feeding upon the nectar 

 and from this habit get the names "Flower or Honey Flies." On hot days they 

 are sometimes very numerous and are called "Sweat Flies" in the Eastern states. 

 They deposit their eggs singly upon leaves and twigs which are infested with 

 plant lice and these give rise to the green larvae. 



While these insects do much to prevent the spread of the plant lice, thej' are 

 in turn preyed upon by other insects. Ants, which foster and protect the plant 

 lice, kill and carry off the larvae in large numbers and greatly reduce their 

 efficiency. Internal parasites also prey upon them. I have hatched a large one 

 from the pupse of Syrphus americanus Wied. Insect Life, Vol III, p. 153, reports 

 the internal parasite Hemiteles syrphicola Ashm. as being reared from Allograpta 

 obliqua Say. 



There are three species here which are doing good work in keeping down the 

 Citrus Plant Lice: a very large species, Lasiophthicus pyrastri Linn., the common 

 Syrphid, Syrphus americanus Wied., and the small species Allograpta obliqua Say. 

 The following brief descriptions of the adult forms have been prepared: 



*Lasiophthicus pyrastri Linn. 

 (Figure 203) 

 This is the largest of the three species named above and measures seven- 

 sixteenths of an inch long. The large compound eyes occupy most of the head 



*NOTE. I am indebted to Prof. C. F. Baker, of Pomona College, for the iden- 

 tification of these species. 



