No. 04] DIPTERA OF CONNECTICUT: MORPHOLOGY 65 



The tarsomeres are usualh' quite slender (Fig. 8, A and G). but 

 in some Diptera, such as the sja^phid shown in Fig, 8, F, they may 

 become fairly broad, and in the syrphid shown in Fig. 8, J, the broad 

 tarsomeres bear long bristles. The basitarsus, ht^ of the fore leg of 

 the empid shown in Fig. 8, H, is greatly enlarged and swollen. The 

 distitarsus, dt., of the fore leg of the male dolichopodid shown in Fig. 

 8,1, is enlarged and compressed, and is clothed with short black hairs; 

 and in the males of the asilid Cyrto'pogon calUdipes, the two distal 

 tarsomeres of the middle leg bear a dense tuft of black bristles on 

 each side, forming a disk of setae, as a secondary sexual character of 

 the male. In the males of the platypezicl Platypcza 'pallipes Lav. 

 {Calotai\^a onmtipes Townsend), and in the males of Calotarsa cal- 

 ceata Townsend, shown in Fig 8, B and C. the first four tarsomeres 

 of the hind leg are strikingly modified and bear peculiar outgrowths 

 occurring o\\\y in the male sex, so that the tarsus appears to be the 

 region of the leg which presents the most striking secondary sexual 

 characters. Minnich (1926-1929) and others have investigated the 

 sensitivity of the tarsi of flies to various chemical stimuli, but the sub- 

 ject is still under discussion. 



Just beyond, or distal to, the last segment oi the tarsus dt of Fig. 

 8, K and L, is a small terminal segment of the leg which may be called 

 the posttarsus or acropod. This snuxll region represents a distinct and 

 separate portion of the leg, although it is usually overlooked in enu- 

 merating the segments of the leg, because of its relative insignificance. 

 This region is called the "praetarsus" by de Meijere, 1901, (although 

 it is posttarsal in position), who homologizes it with the terminal seg- 

 ment, or dactylopodite, of a crustacean limb. 



The unguitractor, u of Fig. 8, K and L, is the principal sclerite of 

 the pretarsus or acropod. The unguitractor muscles, attached to the 

 unguitractor tendon, ut^ draw the unguitractor plate, u^ back into the 

 cavity of the distal segment of the tarsus dt, when they contract. This 

 causes the unguitractor plate u to pull upon the flexor membrane at- 

 tached to the sclerites hu (Fig. 8, L and K) and to the claws un 

 (which are articulated to the dorsal, claw-bearing process or unguifer, 

 at the distal end of the last tarsal segment) , thereby flexing the claws, 

 which become extended again through the natural resiliency of the 

 parts, when the unguitractor muscles relax. The claws, or ungues, 

 un, are usually simple, but may be toothed or dentate in some parasitic 

 forms, etc., as is the case in the hippoboscid shown in Fig. 8, E. 



Immediately bej-ond, or distal to, the unguitractor plate it is the 

 ventral plantar area, Avhich in a few Diptera (such as the Trichocer- 

 idae, Simuliidae, etc.) contains a narrow transverse sclerite called the 

 planta. Two small sclerites (one on each side of the plantar area) 

 called the basij^ulvilli {bu of Fig. 8,L and K) are located at the 

 bases of the pulvilli. />r, or claws, un, and are of fairly wide-spread 

 occurrence in the Diptera. 



In certain Tipulidae, Trichoceridae, etc.. a single median lobe or 

 sac of the acropocl (pretarsus) is developed, and is apparently homol- 

 ogous with the median unpaired structure called the arolium in or- 

 thopteroid insects such as the Blattidae, etc. The writer (Crampton, 



