INTRASEXUAL AGGRESSION IN THE STICK INSECTS 
DIAPHEROMERA VELIEI AND D. COVILLEAE AND 
SEXUAL DIMORPHISM IN THE PHASMATODEA* 
By John Sivinski 
Department of Entomology and Nematology 
University of Florida 
Gainesville, Florida 32611 
Introduction 
Pairing 1 in the Phasmatodea is notable for its duration. The 
Indian stick insect Necroscia sparaxes may remain coupled for up to 
79 days (a record for insects) and accounts of matings lasting days 
or weeks are commonplace (LeFeuvre 1939; Korboot 1961; Gan- 
grade 1963; Gustafson 1966; Clark 1974). Intromission may occur 
only initially or intermittently. In either case, a substantial propor- 
tion of male time-investment is not spent in ejaculate transfer. In 
captivity, Diapheromera veliei and D. covilleae pair for 3 to 136 
hours and the penis may be inserted and removed up to 9 times. The 
genitalia are not in contact for ca. 40% of this period, and 
attachment is maintained by a male clasping organ. 
According to the best current explanation, males remain with 
females when not actively engaged in insemination to guard against 
the introduction of rival ejaculates and so avoid sperm competition 
(the competition of sperm from 2 or more males for the fertilization 
of an ovum; Parker 1971, 1974). Male aggression for possession of 
mating females has been described in a variety of insects (Parker 
1970). In the only account known to me of attempted mate theft by 
a stick insect, an intruding male Orxines macklotti made several 
futile efforts to engage his genitalia, climbed off and walked away 
(Robinson 1965). Also indicative of a passive defense was a 
congregation of Carausius alluaudi collected in the Seychelles 
Islands consisting of 6 males clasping a female’s abdomen at various 
points (a seventh male was nearby) (Bolivar and Ferriero 1912). 
While sedentary guarding of the female might be typical, lack of any 
* Manuscript received by the editor January 27, 1979. 
'The vocabulary describing attachment between male and female is often inade- 
quate for insects. In this paper mating, coupling, and pairing imply continuous 
attachment and not constant intromission. 
395 
