Feeding patterns of a specialist and a generalist grasshopper: electronic monitoring on their host plants

Abstract

Hypochlora alba (Dodge) is a specialist grasshopper that lives and feeds almost exclusively on Artemisia ludoviciana Nutt., a sage plant mostly avoided as food by generalist or polyphagous grasshoppers, such as Melanoplus sanguinipes (Fabr.). Adaptations to feeding on the pubescent sage foliage containing high levels of allelochemics may involve behavioural as well as physiological specialization. Using an electronic device to monitor feeding activity, we compared feeding periodicity, bout length, bout frequency, and overall time spent feeding by H.alba on sage foliage and by M.sanguinipes on seedling ryegrass (Lolium perenne L.), the plants on which they had been reared. Although both species fed for about the same amount of time per day (c. 4–5%), they achieved this by two different feeding patterns. H. alba had feeding bouts averaging c. 10 min each, compared to c. 4–5 min for M.sanguinipes. Bout frequency was reversed, with M.sanguinipes feeding about once every hour and H.alba about half as often. Bout length for both species was unaffected by phase of the photoperiod while bout frequency, and consequently the rate of feeding in min/h, was typically reduced by two‐thirds or more during the dark phase. The relationship of grasshopper feeding behaviour to host plant specialization is discussed.

Attraction of the grasshopper, Melanoplus sanguinipes, to host plant odors and volatile components

“…Because the chemicals we identified in ryegrass odor are commonly emitted from green leaves of a number of potential food plants, they most likely act in concert with vision as general cues for relatively long-distance orientation of grasshoppers to plant foliage. Grasshoppers presumably feed at night, as indicated by laboratory observations and experiments (Simpson, 1982;Blust & Hopkins, 1990); therefore, odor may assume an even greater role in location of potential food plants during that period, when vision would be minimal. Olfactory cues may also elicit initial steps in feeding behavior by grasshoppers in close proximity to their food plants.…”

Compensatory feeding in response to variable food quality by Melanoplus differentialis

“…1). Blust & Hopkins's (1990) electronic device worked well when grasshoppers fed on living plants, but was not sufficiently stable on artificial diets. We modified the circuit to solve this problem ( Fig.…”

“…Feeding monitor. An inexpensive electronic device, modified from that of Blust & Hopkins (1990), was used to monitor the feeding activity of each test insect ( Fig. 1).…”

“…1). Blust & Hopkins (1990) were made to increase the stability of the electronic circuit: we grounded the non-inverting input (+) of the operational amplifier (op-amp) and added a 1 m resistor between this input and the grasshopper in addition to the already existing 4.7 k resistor; we connected a 1 pF capacitor between each power supply pin of the op-amp and ground. To facilitate the observation of circuit functioning, we added a light-emitting diode along with a 680P resistor between the output of the op-amp and ground.…”

“…Much is known about factors affecting meal initiation, duration and termination in the final instar nymphs of the African migratory locust, Locusta migratoria, because of the detailed analyses of their feeding patterns (Bernays & Chapman, 1972;Blaney et al, 1973;Simpson, 1982Simpson, ,1983Simpson, ,1990Simpson & Ludlow, 1986;Simpson et al, 1988). However, in order to generalize results obtained from L.migratoria it is necessary to investigate feeding patterns of different developmental stages as well as responses by many different insect species (Roessingh & Simpson, 1984;Joern et al, 1986;Reynolds et al, 1986;Timmins et al, 1988;Chapman & Beerling, 1990;Blust & Hopkins, 1990;Timmins & Reynolds, 1992).…”