]S"0. 64] DIPTERA OF CONNECTICUT: MORPHOLOGY :25 



the sciarids should be separated from the mycetophilids, and should 

 be grouped with the cecidomyids and scatopsids instead, although nu- 

 merous fundamental resemblances between the sciands and mjxe- 

 tophilids clearh^ indicate that the}' should be grouped together, as is 

 done by most dipterists. 



The compound eyes are contiguous above in many cecidomyids, 

 but in the genera Ti^omiixata (Barnes) and Trisopsis (Kieffer) the 

 lower portions of each eye become separated from the contiguous up- 

 per portions, with the result that there appear to be three compound 

 eyes in these insects, two eyes being lateral and the composite third 

 being dorsal in position. In Trlommafa^ the median dorsal composite 

 eye is connected with the lateral eyes by a narrow strand on each side, 

 but in Trisopsis the connecting strip on each side is lost, and the three 

 distinct parts of the eyes have the appearance of three compound eyes 

 as is shown in Fig. 1, 1. 



When the eyes are contiguous, they are usually approximated 

 above the bases of the antennae, although they may become approxi- 

 mated below the antennae in some empids, dolichopodids and cyrtids. 

 In Oneodes gibhosus (Fig. 1,D) the ej^es are contiguous for a consid- 

 erable distance between the ocelli, o, and the antennae, ant, and widely 

 separate the antennae from the ocelli, while in Acrocera globulus (Fig. 

 1, E) the eyes are contiguous below the antennae, which remain near 

 the ocelli in the latter case. The eyes rarely extend onto the ventral 

 surface of the head, as they do in the mosquito Psorophora, but in 

 some tipulids, such as the males of Erioptera meg ophthalmia^ they are 

 contiguous on the ventral surface of the head behind the rostrum. 



The compound eyes are hugely developed and occupy most of the 

 surface of the head region in certain cj^rtids, pipunculids, etc., while 

 in some of the wingless myrmecophilous and termitophilous phorids, 

 and in the parasitic braulids, streblids and n^ycteribiids, they are 

 I greatly reduced. According to de Meijei-e (1916, p. 51), the com- 

 pound eyes appear to be completely lost in some of the wingless 

 phorids. "streblids and nycteribiids, although minute vestiges of the 

 eyes might escape detection in such small insects, unless they were 

 examined under the higher power of the microscope. 



In the Diptera which live as ectoparasites on various hosts, the 

 ' eyes and antennae alike are reduced, but in other Diptera there is 

 j| frequently a correlation between the development of the eyes and 

 that of the antennae. Thus, in the Nematocera, in which the antennae 

 are longer and are better developed, the eyes are usually smaller with 

 larger facets, while the Orthorrhapha Brachycera and Cyclorrhapha, 

 in which the antennae are shorter and more reduced, usually have 

 somewhat larger eyes with smaller facets, which are more densely 

 crowded together. 



The eyes are usually bare in the Nematocera ; and in the tipulids, 

 for example, only the "Pediciini have short erect setae between the 

 facets. In the Tanyderidae, on the other hand, all of the species have 

 hairs between the facets of the eyes, and in the males of certain bibion- 

 ids, the haii-s on the eyes are long and numerous. Pilose eyes occur 

 more frequently in the"^ higher Diptera and are fomid in some of the 

 stratiomyids. tabanids, empids, cyrtids, ephj^lrids, tachinids, etc. 



